Applications of Photonics, Laser, Plasma and Radiation Physics

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Entropy entropy	2.738	4.7	1999	19.9 Days	2000 CHF	Submit
Photonics photonics	2.536	2.3	2014	13 Days	1800 CHF	Submit
Physics physics	-	2.4	2019	20.9 Days	1400 CHF	Submit
Plasma plasma	-	-	2018	15.2 Days	1200 CHF	Submit
Universe universe	2.813	3.6	2015	19.3 Days	1800 CHF	Submit
Fractal and Fractional fractalfract	3.577	3.6	2017	18.3 Days	1800 CHF	Submit
Condensed Matter condensedmatter	-	3.7	2016	17.8 Days	1400 CHF	Submit

Open AccessCommunication

Hybrid Resonator 1319 nm Nd:YAG InnoSlab Laser

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Photonics 2023, 10(6), 652; https://doi.org/10.3390/photonics10060652 - 05 Jun 2023

Viewed by 216

Abstract

The InnoSlab laser has the advantages of excellent thermal management and high overlapping efficiency. In this work, we report an InnoSlab laser with high efficiency at 1319 nm end-pumped 0.6at.% Nd:YAG by 808 nm. The hybrid stable–unstable resonator was adopted. For a cavity [...] Read more.

The InnoSlab laser has the advantages of excellent thermal management and high overlapping efficiency. In this work, we report an InnoSlab laser with high efficiency at 1319 nm end-pumped 0.6at.% Nd:YAG by 808 nm. The hybrid stable–unstable resonator was adopted. For a cavity length of 17.9 mm and absorbed pumped power of 423.5 W, the output power of 81 W was obtained at T = 5%, exhibiting an optical conversion efficiency of 19.13% and a slope efficiency of 29.80%. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Plasma Treatment of Polystyrene Films—Effect on Wettability and Surface Interactions with Au Nanoparticles

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Plasma 2023, 6(2), 322-333; https://doi.org/10.3390/plasma6020022 - 29 May 2023

Viewed by 285

Abstract

Polystyrene (PS)/Gold (Au) is used for a wide range of applications, including composite nanofibers, catalysis, organic memory devices, and biosensing. In this work, PS films were deposited on silicon substrates via a spin coating technique followed by treatment with argon (Ar) plasma admixed [...] Read more.

Polystyrene (PS)/Gold (Au) is used for a wide range of applications, including composite nanofibers, catalysis, organic memory devices, and biosensing. In this work, PS films were deposited on silicon substrates via a spin coating technique followed by treatment with argon (Ar) plasma admixed with ammonia (NH₃), oxygen (O₂), or tetrafluoroethane (C₂H₂F₄). X-Ray photoelectron spectroscopy (XPS) analysis revealed modified surface chemistry for Ar/O₂, Ar/NH₃, or Ar/C₂H₂F₄ plasma treatment through the incorporation of oxygen, nitrogen, or fluorine groups, respectively. Size-controlled magnetron sputter deposition of Au nanoparticles (NP) onto these plasma-treated PS films was investigated via XPS and AFM techniques. The interaction of the Au NPs, as probed from the XPS and AFM measurements, is discussed by referring to changes in surface chemistry and morphology of the PS after plasma treatment. The results demonstrate the effect of surface chemistry on the interaction of Au NPs with polymer support having different surface functionalities. The XPS results show that significant oxygen surface incorporation resulted from oxygen-containing species in the plasma itself. The surface concentration of O increased from 0.4% for the pristine PS to 4.5 at%, 35.4 at%, and 45.6 at% for the Ar/C₂H₄F₄, Ar/NH₃, and Ar/O₂, respectively. The water contact angle (WCA) values were noticed to decrease from 98° for the untreated PS to 95°, 37°, and 15° for Ar/C₂H₂F₄, Ar/NH₃, and Ar/O₂ plasma-modified PS samples, respectively. AFM results demonstrate that surface treatment was also accompanied by surface morphology change. Small Au islands are well dispersed and cover the surface, thus forming a homogeneous, isotropic structure. The reported results are important for exploiting Au NPs use in catalysis and sensing applications. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

Decryption of Deterministic Phase-Encoded Digital Holography Using Convolutional Neural Networks

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Huang-Tian Chan

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Chi-Ching Chang

Photonics 2023, 10(6), 612; https://doi.org/10.3390/photonics10060612 - 25 May 2023

Viewed by 206

Abstract

Digital holographic encryption is an important information security technology. Traditional encryption techniques require the use of keys to encrypt information. If the key is lost, it is difficult to recover information, so new technologies that allow legitimate authorized users to access information are [...] Read more.

Digital holographic encryption is an important information security technology. Traditional encryption techniques require the use of keys to encrypt information. If the key is lost, it is difficult to recover information, so new technologies that allow legitimate authorized users to access information are necessary. This study encrypts fingerprints and other data using a deterministic phase-encoded encryption system that uses digital holography (DPDH) and determines whether decryption is possible using a convolutional neural network (CNN) using the U-net model. The U-net is trained using a series of ciphertext-plaintext pairs. The results show that the U-net model decrypts and reconstructs images and that the proposed CNN defeats the encryption system. The corresponding plaintext (fingerprint) is retrieved from the ciphertext without using the key so that the proposed method performs well in terms of decryption. The proposed scheme simplifies the decryption process and can be used for information security risk assessment. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

1064/1319 nm Dual-Wavelength Alternating Electro-Optic Q-Switched Laser Based on the Common Q-Switching Bias Voltage

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Photonics 2023, 10(6), 609; https://doi.org/10.3390/photonics10060609 - 24 May 2023

Viewed by 329

Abstract

A dual-wavelength alternating electro-optic (EO) Q-switched laser operating at 1064 and 1319 nm is designed, which takes the structure of double the gain crystals and a single EO modulator with the common Q-switching bias voltage (CQBV). The output characteristics of alternating dual-wavelength pulse [...] Read more.

A dual-wavelength alternating electro-optic (EO) Q-switched laser operating at 1064 and 1319 nm is designed, which takes the structure of double the gain crystals and a single EO modulator with the common Q-switching bias voltage (CQBV). The output characteristics of alternating dual-wavelength pulse lasers are studied via simulations and experiments. The results show that the energy ratio of the two lasing wavelengths can be controlled by changing the CQBV. This is because the CQBV affects the loss of two resonators, 1064 and 1319 nm, at the same time. The gain–loss relationship in the dual-wavelength laser resonators can be controlled by changing the CQBV in a certain range. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Optical Engine Design for a Compact, High-Luminance DLP Projector Using Four-Channel LEDs and a Total Internal Reflection Prism

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Shuihai Peng

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Zhiyao Zhang

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Yong Liu

Photonics 2023, 10(5), 559; https://doi.org/10.3390/photonics10050559 - 11 May 2023

Viewed by 586

Abstract

How to obtain higher brightness with a small volume projection engine for 4K resolution digital light processing (DLP) is of great significance. In this paper, we first use the fourth channel serving as a blue pump leading to a 52% gain of green [...] Read more.

How to obtain higher brightness with a small volume projection engine for 4K resolution digital light processing (DLP) is of great significance. In this paper, we first use the fourth channel serving as a blue pump leading to a 52% gain of green brightness. Secondly, a new inline total internal reflection prism glued with a spherical mirror is constructed to notably reduce the length of the relay illumination system by more than 10 mm, resulting in a more compact optical engine with a volume of 210 × 140 × 36 mm³. Thirdly, a projection lens is optimized with a modulation transfer function higher than 0.6 at 93 lines for a distance of 2125 mm with distortion lower than 1%. As a result, the efficiencies of RGB lights are higher than 60%, and the luminance and uniformity on the screen reach 1412 lm and 94.5% measured by the prototype. Our proposed projection system is significantly helpful for designing a compact and high-luminance 4K DLP projection. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Preliminary Study on Automatic Detection of Hard Defects in Integrated Circuits Based on Thermal Laser Stimulation

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Photonics 2023, 10(5), 540; https://doi.org/10.3390/photonics10050540 - 06 May 2023

Viewed by 307

Abstract

Locating the fault position is a crucial part of the failure mechanism analysis of integrated circuits. This paper proposes a hard defect locating system based on Thermal Laser Stimulation (TLS) technology. The equation for laser-induced changes in the electrical parameters of semiconductor devices [...] Read more.

Locating the fault position is a crucial part of the failure mechanism analysis of integrated circuits. This paper proposes a hard defect locating system based on Thermal Laser Stimulation (TLS) technology. The equation for laser-induced changes in the electrical parameters of semiconductor devices is a good guide to the hardware and software design of the hard defect locating system. The scanning mode of fast total scanning combined with slow point-to-point scanning can quickly locate abnormal areas. A modified median absolute difference (MAD) method is applied to the extraction of anomalous data. The system software can automatically and collaboratively control the 3D mobile station, laser, and signal acquisition unit. It also can intuitively display the distribution of abnormal points on the infrared image. Using a failure MRAM chip and a good one to conduct a comparative test, the abnormal points distributed on the infrared image of the chip indicate that the failure area is in the digital module or eFuse module of the chip, and the Emission Microscopy (EMMI) experiment also verifies the accuracy of the test system. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Study on the Expansion Kinetics of Plasma and Absorption Wave Induced by Millisecond-Nanosecond Combined Pulse Lasers in Fused Quartz

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Photonics 2023, 10(4), 411; https://doi.org/10.3390/photonics10040411 - 06 Apr 2023

Viewed by 572

Abstract

The transient temperature field, the velocity and pressure of plasma, and the absorption wave of fused quartz induced by millisecond-nanosecond combined pulse lasers are simulated. The theoretical model of plasma and absorption wave produced by fused quartz irradiated by a millisecond-nanosecond pulsed laser [...] Read more.

The transient temperature field, the velocity and pressure of plasma, and the absorption wave of fused quartz induced by millisecond-nanosecond combined pulse lasers are simulated. The theoretical model of plasma and absorption wave produced by fused quartz irradiated by a millisecond-nanosecond pulsed laser is established, in which pulse delay and laser energy are essential variables. The results show that the damaged effect of the millisecond-nanosecond combined pulse laser is different under the damaged effect of different pulse delay conditions. When the energy densities of millisecond-nanosecond combined pulse lasers are 800 J/cm² and 20 J/cm², respectively, the range of pulse delay is 0 ms <

Δ t

≤ 3 ms, and the energy coupling efficiency is the highest when

Δ t

= 1 ms. The addition of a nanosecond pulsed laser causes more obvious thermal damage and optical breakdown to fused quartz. The high pressure is concentrated at the plasma expansion interface or the shock wave front. The results can optimize the simulation parameters and be applied to laser plasma processing technology. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

A Cylindrical Optical-Space Black Hole Induced from High-Pressure Acoustics in a Dense Fluid

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Universe 2023, 9(4), 162; https://doi.org/10.3390/universe9040162 - 28 Mar 2023

Viewed by 1410

Abstract

We describe the construction of an optical-space, cylindrical black hole induced by high pressure in a dense fluid. Using an approximate analogy between curved spacetime and optics in moving dielectric media, we derive the mass of the black hole thus created. We describe [...] Read more.

We describe the construction of an optical-space, cylindrical black hole induced by high pressure in a dense fluid. Using an approximate analogy between curved spacetime and optics in moving dielectric media, we derive the mass of the black hole thus created. We describe the resulting optical-space using a Bessel beam profile and Snell’s law to understand how total internal reflection produces a cylindrical, optic black hole. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

Feasibility Demonstration of THz Wave Generation/Modulation Based on Photomixing Using a Single Wavelength-Tunable Laser

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Photonics 2023, 10(4), 369; https://doi.org/10.3390/photonics10040369 - 25 Mar 2023

Viewed by 563

Abstract

The photomixing of two lightwaves is one of the promising methods of generating a terahertz (THz) wave. The conventional photomixing system consisting of two lasers and a modulator results in large transmitter volumes and high power consumption. To solve this issue, we devised [...] Read more.

The photomixing of two lightwaves is one of the promising methods of generating a terahertz (THz) wave. The conventional photomixing system consisting of two lasers and a modulator results in large transmitter volumes and high power consumption. To solve this issue, we devised a novel THz wave generation and modulation system based on photomixing using a single wavelength-tunable laser in combination with delayed self-multiplexing. We successfully demonstrated the feasibility of 300-GHz wave generation and modulation. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Multistage Positron Acceleration by an Electron Beam-Driven Strong Terahertz Radiation

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Photonics 2023, 10(4), 364; https://doi.org/10.3390/photonics10040364 - 24 Mar 2023

Viewed by 610

Abstract

Laser–plasma accelerators (LPAs) have been demonstrated as one of the candidates for traditional accelerators and have attracted increasing attention due to their compact size, high acceleration gradients, low cost, etc. However, LPAs for positrons still face many challenges, such as the beam divergence [...] Read more.

Laser–plasma accelerators (LPAs) have been demonstrated as one of the candidates for traditional accelerators and have attracted increasing attention due to their compact size, high acceleration gradients, low cost, etc. However, LPAs for positrons still face many challenges, such as the beam divergence controlling, large energy spread, and complicated plasma backgrounds. Here, we propose a possible multistage positron acceleration scheme for high energy positron beam acceleration and propagation. It is driven by the strong coherent THz radiation generated when an injected electron ring beam passes through one or more solid targets. Multidimensional particle-in-cell simulations demonstrated that each acceleration stage is able to provide nearly 200 MeV energy gain for the positrons. Meanwhile, the positron beam energy spread can be controlled within 2%, and the beam emittance can be maintained during the beam acceleration and propagation. This may attract one’s interests in potential experiments on both large laser facilities and a traditional accelerator together with a laser system. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Prediction of the Number of Cumulative Pulses Based on the Photon Statistical Entropy Evaluation in Photon-Counting LiDAR

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Entropy 2023, 25(3), 522; https://doi.org/10.3390/e25030522 - 17 Mar 2023

Viewed by 459

Abstract

Photon-counting LiDAR encounters interference from background noise in remote target detection, and the statistical detection of the accumulation of multiple pulses is necessary to eliminate the uncertainty of responses from the Geiger-mode avalanche photodiode (Gm-APD). The cumulative number of statistical detections is difficult [...] Read more.

Photon-counting LiDAR encounters interference from background noise in remote target detection, and the statistical detection of the accumulation of multiple pulses is necessary to eliminate the uncertainty of responses from the Geiger-mode avalanche photodiode (Gm-APD). The cumulative number of statistical detections is difficult to select due to the lack of effective evaluation of the influence of the background noise. In this work, a statistical detection signal evaluation method based on photon statistical entropy (PSE) is proposed by developing the detection process of the Gm-APD as an information transmission model. A prediction model for estimating the number of cumulative pulses required for high-accuracy ranging with the background noise is then established. The simulation analysis shows that the proposed PSE is more sensitive to the noise compared with the signal-to-noise ratio evaluation, and a minimum PSE exists to ensure all the range detections with background noise are close to the true range with a low and stable range error. The experiments demonstrate that the prediction model provides a reliable estimation of the number of required cumulative pulses in various noise conditions. With the estimated number of cumulative pulses, when the signal photons are less than 0.1 per pulse, the range accuracy of 4.1 cm and 5.3 cm are obtained under the background noise of 7.6 MHz and 5.1 MHz, respectively. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

The Acceleration Phenomenon of Shock Wave Induced by Nanosecond Laser Irradiating Silicon Assisted by Millisecond Laser

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Photonics 2023, 10(3), 260; https://doi.org/10.3390/photonics10030260 - 28 Feb 2023

Viewed by 592

Abstract

The propagating evolution of shock waves induced by a nanosecond pulse laser (ns laser) irradiating silicon assisted by a millisecond pulse laser (ms laser) is investigated experimentally. A numerical model of 2D axisymmetric two-phase flow is established to obtain the spatial distribution of [...] Read more.

The propagating evolution of shock waves induced by a nanosecond pulse laser (ns laser) irradiating silicon assisted by a millisecond pulse laser (ms laser) is investigated experimentally. A numerical model of 2D axisymmetric two-phase flow is established to obtain the spatial distribution of shock wave velocity. Two types of shock wave acceleration phenomenon are found. The mechanism of the shock wave acceleration phenomenon is discussed. The experimental and numerical results show that the initial stage of ms laser-induced plasma can provide the initial ions to increase probability of collision ionization between free electrons and vapor atoms. The velocity of the ns laser-induced shock wave is accelerated. Furthermore, the ms laser-induced plasma as the propagation medium can also accelerate the ns laser-induced shock wave. The shock wave acceleration methods obtained in this paper can promote the development of laser propulsion technology. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

Simulation Study of Phase-Driven Multichannel Nano-Optical Conveyor Belt Using Rectangular Gratings

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Photonics 2023, 10(2), 201; https://doi.org/10.3390/photonics10020201 - 13 Feb 2023

Viewed by 649

Abstract

A nano-optical conveyor belt is a unique type of near-field optical tweezer, capable not only of capturing nanoparticles, but also transporting them. In this study, we propose a multichannel nano-optical conveyer, based on a simple rectangular distributed grating array. The design was optimized [...] Read more.

A nano-optical conveyor belt is a unique type of near-field optical tweezer, capable not only of capturing nanoparticles, but also transporting them. In this study, we propose a multichannel nano-optical conveyer, based on a simple rectangular distributed grating array. The design was optimized by varying the number of slits in the gratings, and particle transport was achieved by adjusting the phase difference of the excitation beams. Simulation and calculation results indicate that multiple optical traps and parallel transport channels can be generated by exciting the gratings with four incident beams. The optical force and trapping potential were used to confirm that 20 nm metallic nanoparticles can be stably attracted to the traps and dynamically transported along channels by adjusting the phase of the excitation beams. Compared to existing nano-photon conveyors, this design boasts a straightforward structure and exceptional performance, offering a promising new approach to particle manipulation. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

Quasi-Guided Modes Supported by a Composite Grating Structure with Alternating Element Widths

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Min Sun

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Zhanghua Han

Photonics 2023, 10(2), 110; https://doi.org/10.3390/photonics10020110 - 20 Jan 2023

Viewed by 965

Abstract

The efficiency of many optical processes is significantly dependent on the magnitude of the electric field. In this context, many artificially made resonating structures have been investigated to enhance light–matter interactions and facilitate the creation of practical applications. While metal–based terahertz metamaterials have [...] Read more.

The efficiency of many optical processes is significantly dependent on the magnitude of the electric field. In this context, many artificially made resonating structures have been investigated to enhance light–matter interactions and facilitate the creation of practical applications. While metal–based terahertz metamaterials have been extensively investigated for this purpose, their performances are mainly limited by the poor confinement of terahertz waves on metal surfaces, exhibiting low resonance quality factors. In this work, we propose and investigate a simple yet novel scheme of enhancing wave–matter interactions in the terahertz region by exploiting the phenomenon of quasi–guided modes. The quasi-guided modes with ultra–high quality factors and huge local field enhancement can be achieved by manipulating the guided modes supported by a slab waveguide. The guided modes with the dispersion lines below the light line have infinite Q factors and can not be accessed from external space. By using a new type of composite grating composed of two ridge grating arrays with alternating ridge widths, the grating period is doubled, leading to a folding of the first Brillouin Zone and the flipping of the dispersion lines to be above the light line. Then, the guided modes will be transitioned into new quasi–guided modes with the possibility of free–space excitation while the Q factors are determined by the level of period–doubling perturbation. The presented results of realizing quasi–guided modes can be extended to other structures, providing a novel means of manipulating light–matter interactions. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Influence of Exposure Parameters on Nanoliquid-Assisted Glass Drilling Process Using CO₂ Laser

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Photonics 2023, 10(1), 89; https://doi.org/10.3390/photonics10010089 - 13 Jan 2023

Viewed by 670

Abstract

Liquid-assisted laser processing (LALP) is implemented using a 10.6 μm continuous-wave (CW) CO₂ laser to drill holes in 1.1 mm thick soda-lime glass substrates fully immersed in a nanoliquid bath. The nanoliquid bath consisted of de-ionized water and carbon nano-particles (CNPs) of [...] Read more.

Liquid-assisted laser processing (LALP) is implemented using a 10.6 μm continuous-wave (CW) CO₂ laser to drill holes in 1.1 mm thick soda-lime glass substrates fully immersed in a nanoliquid bath. The nanoliquid bath consisted of de-ionized water and carbon nano-particles (CNPs) of different wt.%. The study focuses on the influence of exposure time (T_E, [s]), laser beam power (P, [W]) and number of pulses (N_P) on resulting geometrical features, namely, crack length (CL, [mm]), inlet diameter (D_INLET, [mm]) and exit diameter (D_EXIT, [mm]). The processed samples were characterized using an optical microscope. Findings show that LALP with investigated ranges of control parameters T_E (0.5–1.5 s), P (20–40 W) and N_P (1–6 pulses) led to successful production of drilled holes having CL range (0.141 to 0.428 mm), D_INLET range (0.406 to 1.452 mm) and D_EXIT range (0.247 to 1.039 mm). It was concluded that increasing T_E alone leads to increasing CL, D_INLET and D_EXIT, while keeping a good balance among the control parameters, especially T_E and N_P, will result in reduced CL values. Moreover, process statistical models were developed using statistical analysis of variance (ANOVA). These models can be used to further understand and control the process within the investigated ranges of control and response parameters. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

1.55 μm Narrow-Linewidth Pulsed Laser Based on MgO:PPLN

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Photonics 2023, 10(1), 77; https://doi.org/10.3390/photonics10010077 - 09 Jan 2023

Viewed by 615

Abstract

A high-power narrow-linewidth 1.55 μm pulsed laser, based on MgO:PPLN OPO, has been achieved using a F–P etalon. The pump source is a 1064 nm acousto-optical (AO) Q-switched Nd:YAG laser with a repetition rate of 10 kHz. Under the maximum pump power of [...] Read more.

A high-power narrow-linewidth 1.55 μm pulsed laser, based on MgO:PPLN OPO, has been achieved using a F–P etalon. The pump source is a 1064 nm acousto-optical (AO) Q-switched Nd:YAG laser with a repetition rate of 10 kHz. Under the maximum pump power of 18 W, the signal output power of 2.57 W is demonstrated at 1551.1 nm with a linewidth of 0.07 nm, corresponding to a slope efficiency of 16.1%. Different from traditional inversion lasers, the narrow-linewidth wavelength tunability of approximately 1.55 μm can be realized by changing the temperature. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Efficient Third-Harmonic Generation by Inhomogeneous Quasi-Phase-Matching in Quadratic Crystals

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Obid I. Sabirov

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Gaetano Assanto

and

Usman K. Sapaev

Photonics 2023, 10(1), 76; https://doi.org/10.3390/photonics10010076 - 09 Jan 2023

Viewed by 590

Abstract

We investigate the generation of optical third-harmonic frequency in quadratic crystals with a nonlinear domain lattice optimized with the aid of a random number generator. In the developed Monte Carlo algorithm and numerical experiments, we consider domain thicknesses to be taking either the [...] Read more.

We investigate the generation of optical third-harmonic frequency in quadratic crystals with a nonlinear domain lattice optimized with the aid of a random number generator. In the developed Monte Carlo algorithm and numerical experiments, we consider domain thicknesses to be taking either the values d₁ or d₂, with d₁ and d₂ being the coherence lengths for the cascaded parametric interactions

2 ω = ω + ω

and

3 ω = 2 ω + ω

, respectively. We focus on the cases with single segments formed by equal and/or different domains, showing that frequency tripling can be achieved with high conversion efficiency from an arbitrary input wavelength. The presented approach allows one to accurately determine the optimized random alternation of domain thicknesses d₁ and d₂ along the propagation length. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Critical Laser Intensity of Phase-Matched High-Order Harmonic Generation in Noble Gases

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Photonics 2023, 10(1), 24; https://doi.org/10.3390/photonics10010024 - 26 Dec 2022

Viewed by 788

Abstract

The efficient generation of high-order harmonic radiation has been a challenging task since the early days of strong-field physics. An essential requirement to achieve efficient high-order harmonic generation inside a gas medium is the phase matching of the high-order harmonic radiation and the [...] Read more.

The efficient generation of high-order harmonic radiation has been a challenging task since the early days of strong-field physics. An essential requirement to achieve efficient high-order harmonic generation inside a gas medium is the phase matching of the high-order harmonic radiation and the incident laser pulse. The dominant contribution to the wave–vector mismatch

Δ k

is associated with the ionization probability of the medium. In this work, we derive two analytical formulas to calculate the critical intensity of a general linearly polarized laser pulse that obey the phase-matching condition

Δ k = 0

. The analytic formulas are valid in the tunneling regime (ADK model) and the regime of the tunnel and multi-photon ionization (PPT model), respectively. We compare our results to numerical computations and discuss the scaling of the critical intensity depending on the pulse duration and the wavelength of a realistic incident laser pulse. The analytical approach demonstrated in this work is highly accurate and can compete with the existing numerical computational methods by an error of less than 1% and a decrease in the computation time of approximately 4 to 6 orders of magnitude. This enables complex theoretical studies of the efficiency scaling in HHG or to consider the effects of ground state depletion efficiently. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Effect of Lidar Receiver Field of View on UAV Detection

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Photonics 2022, 9(12), 972; https://doi.org/10.3390/photonics9120972 - 11 Dec 2022

Viewed by 744

Abstract

Researchers have shown that single-photon light detection and ranging (lidar) is highly sensitive and has a high temporal resolution. Due to the excellent beam directivity of lidar, most applications focus on ranging and imaging. Here, we present a lidar detection system for night [...] Read more.

Researchers have shown that single-photon light detection and ranging (lidar) is highly sensitive and has a high temporal resolution. Due to the excellent beam directivity of lidar, most applications focus on ranging and imaging. Here, we present a lidar detection system for night environments. Different from MEMS, we choose a large divergence rather than scanning to detect unmanned aerial vehicles (UAVs). Collection and detection are achieved through the use of high-efficiency optical devices. With time-correlated single photon counting (TCSPC), we performed subsequent drone search work at centimeter resolution. We believe that we have developed a new technique for detecting UAVs. We show how the field of view influences the detection process. For some key areas of air defense, it is extremely necessary to find UAVs quickly and in a timely manner. In short, the results represent an important step toward practical, low-power drone detection using lidar. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Laser Driven Electron Acceleration from Near-Critical Density Targets towards the Generation of High Energy γ-Photons

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Iuliana-Mariana Vladisavlevici

,

Daniel Vizman

and

Emmanuel d’Humières

Photonics 2022, 9(12), 953; https://doi.org/10.3390/photonics9120953 - 09 Dec 2022

Cited by 2 | Viewed by 732

Abstract

In this paper, we investigate the production of high energy gamma photons at the interaction between an ultra-high intensity laser pulse with an energetic electron beam and with a near-critical density plasma for the laser intensity varying between

10^{19}

–

10^{23}

[...] Read more.

In this paper, we investigate the production of high energy gamma photons at the interaction between an ultra-high intensity laser pulse with an energetic electron beam and with a near-critical density plasma for the laser intensity varying between

10^{19}

–

10^{23}

W/cm

^{2}

. In the case of the interaction with an electron beam, and for the highest laser intensities considered, the electrons lose almost all their energy to emit gamma photons. In the interaction with a near-critical density plasma, the electrons are first accelerated by the laser pulse up to GeV energies and further emit high energy radiation. A maximum laser-to-photons conversion coefficient of

30 %

is obtained. These results can be used for the preparation of experiments at the Apollon and ELI laser facilities for the investigation of the emission of high energy

γ

-photons and to study the electron-positron pair creation in the laboratory. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Photonic Integrated Circuit for Optical Phase Control of 1 × 4 Terahertz Phased Arrays

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Photonics 2022, 9(12), 902; https://doi.org/10.3390/photonics9120902 - 25 Nov 2022

Cited by 1 | Viewed by 1296

Abstract

In this manuscript, we report on a 1 × 4 optical beam forming network (OBFN) chip using optical phase shifters (OPSs) based on thermo-optically controlled optical ring resonators (ORRs) for 1D beam steering at 0.3 THz. The 1 × 4 OBFN chip consists [...] Read more.

In this manuscript, we report on a 1 × 4 optical beam forming network (OBFN) chip using optical phase shifters (OPSs) based on thermo-optically controlled optical ring resonators (ORRs) for 1D beam steering at 0.3 THz. The 1 × 4 OBFN chip consists of four OPSs and is fabricated using TriPleX technology. Each of the four OPSs is realized by two cascaded identical ORRs, to reach a phase shift of 2π. To allow transfer of the optical phase shift to the THz domain by optical heterodyning in high-frequency 1.55 µm modified uni-travelling carrier photodiodes, the ORRs are designed such that one carrier of the optical heterodyne signal is at the ORR’s resonance frequency, whereas the second optical heterodyne signal is at its off-resonance. By adjusting the resonance frequencies of the two ORRs in each OPS synchronously, a relative phase variation between two optical heterodyne carriers of up to 2π with a tuning efficiency of 0.058 W/π, is experimentally demonstrated. Due to the dispersive power transmission loss of the ORRs, phase tuning leads to a power variation of the optical heterodyne-generated signals up to 3.8 dB, which is experimentally characterized at 0.295 THz. It is shown numerically that this power variation only has a minor impact on the steering performance of a 1 × 4 phased array. The determined beam direction deviation and maximum absolute radiation power change are smaller than 1° and 2 dB, respectively. By sweeping the phase difference between two adjacent THz antennas in the 1 × 4 phased array, from −120° to 120°, a beam steering range of ~62° is demonstrated numerically at 0.295 THz. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Collisions of Electrons with Alkali, Alkaline and Complex Atoms Relevant to Solar and Stellar Atmospheres

by

Moncef Derouich

,

Saleh Qutub

,

Fainana Mustajab

and

Badruddin Zaheer Ahmad

Universe 2022, 8(12), 613; https://doi.org/10.3390/universe8120613 - 23 Nov 2022

Viewed by 570

Abstract

In solar and stellar atmospheres, atomic excitation by impact with electrons plays an important role in the formation of spectral lines. We make use of available experimental and theoretical cross-sections to calculate the excitation rates in s–p transitions of alkali and [...] Read more.

In solar and stellar atmospheres, atomic excitation by impact with electrons plays an important role in the formation of spectral lines. We make use of available experimental and theoretical cross-sections to calculate the excitation rates in s–p transitions of alkali and alkaline atoms through collisions with electrons. Then, we infer a general formula for calculating the excitation rates by using genetic programming numerical methods. We propose an extension of our approach to deduce collisional excitation rates for complex atoms and atoms with hyperfine structure. Furthermore, the developed method is also applied to determine collisional polarization transfer rates. Our results are not specific to a given atom and can be applied to any s–p atomic transition. The accuracy of our results is discussed. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Decoherence of Higher Order Orbital Angular Momentum Entangled State in Non-Kolmogorov Turbulence

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Photonics 2022, 9(11), 808; https://doi.org/10.3390/photonics9110808 - 27 Oct 2022

Viewed by 649

Abstract

The decay of OAM entanglement in non-Kolmogorov turbulence has been numerically evaluated. In this work, we explore the evolution of OAM entanglement with higher-order OAM mode in the weak scintillation regime. In particular, the results of the numerical evaluation show that the OAM [...] Read more.

The decay of OAM entanglement in non-Kolmogorov turbulence has been numerically evaluated. In this work, we explore the evolution of OAM entanglement with higher-order OAM mode in the weak scintillation regime. In particular, the results of the numerical evaluation show that the OAM entanglement state with higher value of the azimuthal mode and larger radial quantum number survives over a longer distance. Meanwhile, the beam parameters and turbulence parameters usually have significant influences on OAM entanglement. In addition, it is demonstrated that the effect of turbulence on the OAM entanglement is the most serious when the generalized exponent is around 3.07. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Thermodynamic Functions of a Metal Exposed to High Energy Densities in Compressed and Expanded States

by

Nikolay B. Volkov

and

Alexander I. Lipchak

Condens. Matter 2022, 7(4), 61; https://doi.org/10.3390/condmat7040061 - 27 Oct 2022

Viewed by 817

Abstract

The development of a wide-range phenomenological model of metal with a small number of adjustable parameters for studying the behavior of metals in expanded and compressed states under the exposition of high energy density fluxes is the objective of the paper present. Both [...] Read more.

The development of a wide-range phenomenological model of metal with a small number of adjustable parameters for studying the behavior of metals in expanded and compressed states under the exposition of high energy density fluxes is the objective of the paper present. Both the reference data, methods of the quantum-statistical model of the atom, the density functional theory, and the requirement to the expanded and compressed states description of metal should be consistent on their boundary were used in the model. The expressions for thermodynamic functions and the critical parameters of expanded iron were obtained within the framework of the soft sphere model. The Grüneisen parameters calculated for the expanded and compressed states of the metal appear to be in good agreement with each other was shown. A calculation technique of the ion component average charge of the metal in expanded and compressed states is proposed. The experimentally defined volume range of V/V₀ = 3–4 in which the character of iron conductivity changes from metallic to non-metallic includes the obtained in frameworks of our approach value of the critical volume: V/V₀ = 3.802 was established. The behavior of the average charge of the ion component is discussed. The contribution of the thermal electrons to the thermodynamic functions is evaluated. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Dual-Wavelength Continuous-Wave and Passively Q-Switched Alexandrite Laser at 736.7 nm and 752.8 nm

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Photonics 2022, 9(10), 769; https://doi.org/10.3390/photonics9100769 - 14 Oct 2022

Cited by 1 | Viewed by 814

Abstract

A dual-wavelength continuous-wave (CW) and passively Q-switched alexandrite laser based on a MoS₂ saturable absorber (SA) operating at 736.7 nm and 752.8 nm with a simple and compact 18 mm plano–plano resonator is reported. In the CW mode, the output power is [...] Read more.

A dual-wavelength continuous-wave (CW) and passively Q-switched alexandrite laser based on a MoS₂ saturable absorber (SA) operating at 736.7 nm and 752.8 nm with a simple and compact 18 mm plano–plano resonator is reported. In the CW mode, the output power is 1014 mW at the linear-polarized pump power of 5.44 W, with a slope efficiency of 28.7%. In the pulsed operation, the narrowest pulse width and the maximal peak power are 154 ns and 10.6 W, respectively. This laser can be used to generate 8.71 THz-wave light based on a suitable nonlinear optical crystal. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

Tunable High-Q Factor Substrate for Selectively Enhanced Raman Scattering

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Photonics 2022, 9(10), 755; https://doi.org/10.3390/photonics9100755 - 11 Oct 2022

Cited by 1 | Viewed by 741

Abstract

Most Surface-enhanced Raman scattering (SERS) substrates enhance all the Raman signals in a relative broad spectral range. The substrates enhance both the interested and background signals together. To improve the identification of target molecules from numerous background ones, substrates with multi high-quality (Q) [...] Read more.

Most Surface-enhanced Raman scattering (SERS) substrates enhance all the Raman signals in a relative broad spectral range. The substrates enhance both the interested and background signals together. To improve the identification of target molecules from numerous background ones, substrates with multi high-quality (Q) factor resonance wavelengths can be designed to achieve the selective enhancement of specific Raman transitions. When the resonance frequencies are modulated to match the excitation and Raman scattering frequencies, the detection of the target molecule can be more effective. In this paper, we design a tunable high-Q SERS substrate with periodic silver bowtie nanoholes on silica spacer and silver film. The substrate possessed three high-Q and high electric field resonance modes, which resulted from the interaction of the localized surface plasmon resonance (LSPR) of the bowtie nanoholes, the surface plasmon polariton (SPP) of the period bowtie nanoholes and the Fabry–Perot (FP) resonance between the bowtie and silver film bottom. The interaction between these resonance modes resulted in not only a higher quality (Q) factor, but also a higher electric field, which can be employed to realize a potential substrate in high-sensitivity and selective-detection fields. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

Optical-Frequency-Comb Generation Based on Single-Tone Modulation and Four-Wave Mixing Effect in One Single Semiconductor Optical Amplifier

by

Zeyu Tan

and

Lirong Huang

Photonics 2022, 9(10), 746; https://doi.org/10.3390/photonics9100746 - 09 Oct 2022

Viewed by 953

Abstract

We propose a novel optical-frequency-comb (OFC) generation scheme based on single-tone modulation and the four-wave mixing (FWM) effect in one single semiconductor optical amplifier (SOA) modulated by a radio frequency (RF) current. A comprehensive broad-band dynamic model, which considers single-tone modulation and the [...] Read more.

We propose a novel optical-frequency-comb (OFC) generation scheme based on single-tone modulation and the four-wave mixing (FWM) effect in one single semiconductor optical amplifier (SOA) modulated by a radio frequency (RF) current. A comprehensive broad-band dynamic model, which considers single-tone modulation and the FWM effect, is presented. The simulated results show that, although only one single continuous-wave light is input into the SOA, an OFC with a large number of frequency components can be achieved as a result of single-tone modulation and the FWM effect in the SOA. The number of comb lines and the spectral bandwidth of the OFC increase by raising the amplitude of the RF modulation current. Increasing the input light power can increase the average optical power of the OFC. The frequency interval is tunable within a certain range by tuning the frequency of the RF modulation current injected into the SOA. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Programmable Parallel Optical Logic Gates on a Multimode Waveguide Engine

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Photonics 2022, 9(10), 736; https://doi.org/10.3390/photonics9100736 - 08 Oct 2022

Cited by 2 | Viewed by 979

Abstract

Optical logic gates have been proposed and demonstrated on a function programmable waveguide engine constructed using buried silicon nitride waveguides in polymer and a set of thermal electrodes. The device can perform logic AND or OR operations for the input signals A and [...] Read more.

Optical logic gates have been proposed and demonstrated on a function programmable waveguide engine constructed using buried silicon nitride waveguides in polymer and a set of thermal electrodes. The device can perform logic AND or OR operations for the input signals A and B, each containing two bits of information, in parallel. The input signals, in the form of binary current values in the electronic domain, are applied to a subset of thermal electrodes, while the computed logic states are converted to optical intensity variations at the single-mode waveguide outputs. The rest of the electrodes work as weights to define the device function, either AND or OR, by adjusting the light interference in the multimode waveguide through thermo-optic effect. Simulations were first performed to reveal the nonlinear response of the received light intensity with respect to the applied current, thus allowing complex and effective manipulation of the light field on the waveguide engine. After chip fabrication and system integration, 65,536 experiments were performed automatically. The data are fed into a sorting program to find the valid settings that satisfy the respective truth table out of the 283,852,800 possible input/weight/output combinations. Four cases of operations for the AND and OR gates are presented in the end, with different bar and contrast values. This simple, low-cost yet powerful engine may be further developed for applications in on-chip photonic computing and signal switching. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

Theoretical and Experimental Investigations of Tunable Microwave Signal Generation Based on a 1-GHz All-Polarization-Maintaining Mode-Locked Fiber Laser

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and

Photonics 2022, 9(10), 717; https://doi.org/10.3390/photonics9100717 - 01 Oct 2022

Viewed by 761

Abstract

Photonics-based microwave generation brings the advantages of photonic oscillators, such as high stability, wide bandwidth, and low loss, to the microwave domain. In this paper, the generation of tunable microwave signals was investigated both theoretically and experimentally based on an all-polarization-maintaining 1-GHz mode-locked [...] Read more.

Photonics-based microwave generation brings the advantages of photonic oscillators, such as high stability, wide bandwidth, and low loss, to the microwave domain. In this paper, the generation of tunable microwave signals was investigated both theoretically and experimentally based on an all-polarization-maintaining 1-GHz mode-locked fiber laser. Based on beating between two highly chirped optical pulse trains with a relative time delay at the photodetector, tunable microwave signals could be obtained. The numerical simulations show that 40 GHz or higher microwave signals could be obtained by tuning the time delay and dispersion. To experimentally validate the theoretical model, the generation of tunable microwave signals from 2–4 GHz was demonstrated. Due to the utilization of polarization-maintaining devices, the optical output has a high degree of linear polarization of more than 99%, which verifies the enhanced system stability. These demonstrations are imperative for solidifying the advancements of recent years and could promote the utilization of photonics-based microwave generation in microwave photonics. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Goos–Hänchen Lateral Displacements and Angular Deviations: When These Optical Effects Offset Each Other

by

Stefano De Leo

,

Luca Maggio

and

Moreno d’Ambrosio

Photonics 2022, 9(9), 643; https://doi.org/10.3390/photonics9090643 - 07 Sep 2022

Cited by 1 | Viewed by 850

Abstract

For optical beams transmitted by a right-angle prism, the Goos–Hänchen shift can never be seen as a pure effect. Indeed, the lateral displacement, caused by the total internal reflection, will always be accompanied by angular deviations generated by the transmission through the incoming [...] Read more.

For optical beams transmitted by a right-angle prism, the Goos–Hänchen shift can never be seen as a pure effect. Indeed, the lateral displacement, caused by the total internal reflection, will always be accompanied by angular deviations generated by the transmission through the incoming and outgoing interfaces. This combined effect can be analyzed by using the Taylor expansion of the Fresnel coefficients. The analytic expression found for the transmitted beam allows us to determine the beam parameters, the incidence angles, and the axial distance for which lateral displacements are compensated by angular deviations. Proposals to optimize experimental implementations are also briefly discussed. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

A Plasma-Based Decontamination Process Reveals Potential for an in-Process Surface-Sanitation Method

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Plasma 2022, 5(3), 351-365; https://doi.org/10.3390/plasma5030027 - 06 Sep 2022

Cited by 1 | Viewed by 888

Abstract

Methods, which use an indirect plasma treatment for the inactivation of microorganisms in foods, claim a vastly growing field of research. This paper presents a method that uses plasma-processed air (PPA) as a sanitizer. In addition to a sanitation concept for the decontamination [...] Read more.

Methods, which use an indirect plasma treatment for the inactivation of microorganisms in foods, claim a vastly growing field of research. This paper presents a method that uses plasma-processed air (PPA) as a sanitizer. In addition to a sanitation concept for the decontamination of produce in the value chain, the presented method offers a possible application as an “in-process” surface sanitation. PPA provides antimicrobial-potent species, which are predominantly reactive nitrogen species (RNS); this has an outstanding groove penetration property. In an experimental approach, surfaces, made from materials, which are frequently used for the construction of food-processing plants, were inoculated with different microorganisms. Listeria monocytogenes (ATCC 15313), Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 10538), Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 43971), and Salmonella enterica subsp. enterica serovar Enteritidis (ATCC 13076) are all microorganisms that frequently appear in foods and possess the risk for cross-contamination from the plant to the produce or vice versa. The contaminated samples were treated for various treatment times (1–5 min) with PPA of different antimicrobial potencies. Subsequently, the microbial load on the specimens was determined and compared with the load of untreated samples. As a result, reduction factors (RF) up to several log₁₀-steps were obtained. Although surface and the bacterial strain showed an influence on the RF, the major influence was seen by a prolongation of the treatment time and an increase in the potency of the PPA. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Polarization-Insensitive Graphene Modulator Based on Hybrid Plasmonic Waveguide

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Photonics 2022, 9(9), 609; https://doi.org/10.3390/photonics9090609 - 28 Aug 2022

Cited by 3 | Viewed by 885

Abstract

A polarization-insensitive graphene-assisted electro-optic modulator is proposed. The orthogonal T-shaped metal slot hybrid plasmonic waveguide allows the polarization-independent propagation of transverse electric field mode and complex mode. By the introduction of dual-layer graphene on the ridge waveguide, the polarization-insensitive modulation depths of the [...] Read more.

A polarization-insensitive graphene-assisted electro-optic modulator is proposed. The orthogonal T-shaped metal slot hybrid plasmonic waveguide allows the polarization-independent propagation of transverse electric field mode and complex mode. By the introduction of dual-layer graphene on the ridge waveguide, the polarization-insensitive modulation depths of the TE mode and complex mode are 0.511 dB/µm and 0.502 dB/µm, respectively. The 3 dB bandwidth of the modulator we have proposed is about 127 GHz at the waveguide length of 20 μm. The power consumption of 72 fJ/bit promised potential graphene electro-optic modulator applications for on-chip interconnected information transfer and processing. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessCommunication

Holographic Encryption Applications Using Composite Orbital Angular Momentum Beams

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Photonics 2022, 9(9), 605; https://doi.org/10.3390/photonics9090605 - 26 Aug 2022

Viewed by 1043

Abstract

Optical orbital angular momentum (OAM) holography has been developed and implemented as a vital method for optical encryption. However, OAM holography can only be encoded and decoded with an OAM beam, which limits the level of optical encryption. Here, composite OAM beams are [...] Read more.

Optical orbital angular momentum (OAM) holography has been developed and implemented as a vital method for optical encryption. However, OAM holography can only be encoded and decoded with an OAM beam, which limits the level of optical encryption. Here, composite OAM beams are introduced using a computer-generated hologram (CGH) for holographic encryption. The target image is encoded with composite helical mode indices, and the OAM holographic image can only be reconstructed under a specific illuminating composite OAM beam. The experimental results are consistent with the theoretical design and numerical simulations, verifying that composite OAM beams can provide a higher security level for optical holographic encryption. The proposed method can be used to enhance anti-counterfeiting applications, secure communication systems, and imaging systems. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

High-Power, Narrow-Linewidth Distributed-Feedback Quantum-Cascade Laser for Molecular Spectroscopy

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Photonics 2022, 9(8), 589; https://doi.org/10.3390/photonics9080589 - 19 Aug 2022

Viewed by 1150

Abstract

Quantum cascade lasers are versatile light sources in the mid-infrared range for molecular spectroscopy which find a wide range of applications from high-resolution studies to sensing. While devices with either high power or narrow spectral linewidth have previously been reported, there is still [...] Read more.

Quantum cascade lasers are versatile light sources in the mid-infrared range for molecular spectroscopy which find a wide range of applications from high-resolution studies to sensing. While devices with either high power or narrow spectral linewidth have previously been reported, there is still a lack of sources combining both of these characteristics which are particularly important for precision measurements of weak spectroscopic transitions. In this article, we describe and characterize a novel master-oscillator power-amplifier distributed-feedback quantum cascade laser designed to fill this gap. At an output power of 300 mW, the device features a free-running linewidth of 1.3 MHz, measured with a frequency discriminator technique, at an emission wavenumber of 2185 cm

^{- 1}

. This linewidth is sufficiently narrow to enable a further reduction by a tight lock to a high-Q oscillator. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Design of a Broadband Perfect Solar Absorber Based on a Four-Layer Structure with a Cross-Shaped Resonator and Triangular Array

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Photonics 2022, 9(8), 565; https://doi.org/10.3390/photonics9080565 - 11 Aug 2022

Cited by 1 | Viewed by 1001

Abstract

As solar energy is a low-cost and clean energy source, there has been a great deal of interest in how to harvest it. To absorb solar energy efficiently, we designed a broadband metamaterial absorber based on the principle of Fabry–Pérot (FP) cavities and [...] Read more.

As solar energy is a low-cost and clean energy source, there has been a great deal of interest in how to harvest it. To absorb solar energy efficiently, we designed a broadband metamaterial absorber based on the principle of Fabry–Pérot (FP) cavities and surface plasmon resonance (SPR). We propose a broadband perfect absorber consisting of a four-layer structure of silica–tungsten–silica–titanium (SiO₂–W–SiO₂–Ti) for the incident light wavelength range of 300–2500 nm. The structure achieves perfect absorption of incident light in the wavelength range of 351.8–2465.0 nm (absorption > 90%), with an average absorption of 96.3%. The advantage of our proposed structure is that it combines the characteristics of both high and broadband absorption, and has high overall absorption efficiency for solar radiation. It is also independent of polarization and insensitive to incident angle. We investigated how absorption was affected by different structures, materials, geometric parameters, and refractive indices for different dielectric materials, and we explored the reasons for high absorption. This structure is refractory and ultrathin, and it offers a good tradeoff between bandwidth and absorption. It therefore has premium application prospects and value. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Planar Waveguide-Based Fiber Spectrum Analyzer Mountable to Commercial Camera

by

Xinhong Jiang

and

Ziyang Zhang

Photonics 2022, 9(7), 456; https://doi.org/10.3390/photonics9070456 - 28 Jun 2022

Viewed by 912

Abstract

We present the design of a planar spectrometer that separates the wavelength channels from an input fiber and focuses the spectral lines onto a camera without any free-space optical elements. The geometric arrangements of the waveguides to achieve different spectroscopic parameters are explained [...] Read more.

We present the design of a planar spectrometer that separates the wavelength channels from an input fiber and focuses the spectral lines onto a camera without any free-space optical elements. The geometric arrangements of the waveguides to achieve different spectroscopic parameters are explained in detail, allowing adjustable focal lengths, high spectral resolution, and broad free spectral range. The optical chip is fabricated on a low-cost polymer platform as proof of concept. The optical spectrum of a multiwavelength laser is measured by the proposed device, and the result is in good agreement with a commercial optical spectrum analyzer. The large focal depth of the chip allows an optical assembly of much relaxed alignment accuracy. We demonstrate a tube design to encapsulate the chip fixed with the input fiber. The assembly is then mounted to a commercial camera with standard C-mount threading as a convenient fiber spectrum analyzer without customized detectors and circuits. Our design may provide a low-cost and versatile solution for the development of compact spectroscopic equipment. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Beam Smoothing Based on Prism Pair for Multistep Pulse Compressor in PW Lasers

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Photonics 2022, 9(7), 445; https://doi.org/10.3390/photonics9070445 - 23 Jun 2022

Cited by 1 | Viewed by 1076

Abstract

Ultra-short, ultra-intense lasers provide unprecedented experimental tools and extreme physical conditions, enabling the exploration of the frontiers of basic physics. Recently, a multistep pulse compressor (MPC) method was proposed to overcome the limitations of the size and the damage threshold of gratings in [...] Read more.

Ultra-short, ultra-intense lasers provide unprecedented experimental tools and extreme physical conditions, enabling the exploration of the frontiers of basic physics. Recently, a multistep pulse compressor (MPC) method was proposed to overcome the limitations of the size and the damage threshold of gratings in the compressor for the realization of a higher-peak-power laser. In the MPC method, beam smoothing is an important process in the pre-compressor. In this study, beam smoothing based on prism pairs is investigated, and the spatial profiles, as well as spectral dispersion properties, are analyzed. The simulation results demonstrate that the prism pair can effectively smooth the laser beam. Furthermore, beam smoothing is found to be more efficient with a shorter separation distance if two prism pairs are arranged to induce spatial dispersion in one or two directions. The beam smoothing results obtained in this study will help optimize optical designs in petawatt (PW) laser systems, thereby improving their output and operational safety. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

All-Dielectric Structural Colors with Lithium Niobate Nanodisk Metasurface Resonators

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Photonics 2022, 9(6), 402; https://doi.org/10.3390/photonics9060402 - 08 Jun 2022

Cited by 2 | Viewed by 1548

Abstract

Lithium niobate (LN) is a promising optical material, its micro–nano structures have been applied to fields such as photonic crystals, nonlinear optics, optical waveguides, and so on. At present, lithium niobate structural colors are rarely studied. Although the nanograting structure was researched, it [...] Read more.

Lithium niobate (LN) is a promising optical material, its micro–nano structures have been applied to fields such as photonic crystals, nonlinear optics, optical waveguides, and so on. At present, lithium niobate structural colors are rarely studied. Although the nanograting structure was researched, it has such large full width at half-maximum (fwhm) that it cannot achieve red, green, or blue pixels or other high-saturation structural colors, thus, its color printing quality is poor. In this paper, we design and simulate lithium niobate nanodisk metasurface resonators (LNNDMRs), which are based on Mie magnetic dipole (MD) and electric dipole (ED) resonances. In addition, the resonators yield very narrow reflection peaks and high reflection efficiencies with over 80%, especially the reflection peaks of red, green, and blue pixels with fwhm around 11 nm, 9 nm, and 6 nm, respectively. Moreover, output colors of different array cells composed of single nanodisk in finite size are displayed, which provides a theoretical basis for their practical applications. Therefore, LNNDMRs pave the way for high-efficiency, compact photonic display devices based on lithium niobate. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Characteristics of a Source for Oxide Coating Deposition by the Electron-Beam Evaporation of Dielectric Materials

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Plasma 2022, 5(2), 258-264; https://doi.org/10.3390/plasma5020020 - 25 May 2022

Cited by 1 | Viewed by 1173

Abstract

We describe our investigations of a plasma-cathode electron source designed for the deposition of oxide coatings by the electron-beam evaporation of dielectric materials. Tests carried out using oxygen as the working gas showed that the source is operable without a change in parameters [...] Read more.

We describe our investigations of a plasma-cathode electron source designed for the deposition of oxide coatings by the electron-beam evaporation of dielectric materials. Tests carried out using oxygen as the working gas showed that the source is operable without a change in parameters for at least ten hours of continuous operation. The current–voltage characteristics of the hollow-cathode plasma source in oxygen displayed a monotonically increasing character, and the voltage dependence of the discharge current was exponential. At the same time, for argon, nitrogen, and helium, the discharge voltage remained unchanged over a current ranging from 0.1 A to 1 A. A possible reason for these differences is the formation of oxides on the electrode surfaces for operation in the oxygen, impeding the discharge operation and requiring higher voltages for the same current as the other gases. The dependencies of the electron beam current on the accelerating voltage were monotonically increasing curves for all the gases except for helium, for which the beam current remained unchanged with increasing voltage over a range from two to ten kilovolts. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Open AccessArticle

Optical Properties of Black Carbon Aerosols with Different Coating Models

by

Yanxia Tang

,

Yong Huang

and

Keyong Zhu

Photonics 2022, 9(5), 359; https://doi.org/10.3390/photonics9050359 - 19 May 2022

Viewed by 1291

Abstract

Research on the optical properties of black carbon (BC) aerosols is highly important for investigating global climate change. A general inhomogeneous particle superposition model is developed. Inhomogeneous particles with arbitrary shapes can be constructed by this model. BC aerosols with core-shell, spherical, ellipsoid, [...] Read more.

Research on the optical properties of black carbon (BC) aerosols is highly important for investigating global climate change. A general inhomogeneous particle superposition model is developed. Inhomogeneous particles with arbitrary shapes can be constructed by this model. BC aerosols with core-shell, spherical, ellipsoid, and irregular coating models are established to explore the impact of coating shape on their optical properties. The optical properties are studied employing the discrete dipole approximation method (DDA). The influences of the morphology of BC aerosols, the coating volume fractions, and the shape of coatings on the optical properties are analyzed. The irregular coating shape causes a higher forward scattering intensity and a lower extinction cross-section. The forward scattering intensity of the core-shell model is lower than other models. The effect of the coating shape on forward scattering intensity becomes smaller as coating volume and fractal dimension increase. Consequently, assuming irregular coating as spherical coating models considered in most studies leads to inaccuracy in the optical properties of BC aerosols. It is necessary to comprehensively consider the effects of aerosol morphology and coating volume for investigating the optical properties of black carbon aerosols. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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Spurious Tone Reduction and Signal Stabilization of Optoelectronic Oscillators by Low-Frequency RF Signal Modulation

by

Jun-Hyung Cho

,

Hyo-Sang Jeong

and

Hyuk-Kee Sung

Photonics 2022, 9(5), 339; https://doi.org/10.3390/photonics9050339 - 12 May 2022

Cited by 1 | Viewed by 1271

Abstract

In this study, the oscillation signal stabilization and spurious tone suppression of a directly modulated optoelectronic oscillator (DM-OEO) are simultaneously achieved by modulating a laser with a low-frequency radio frequency (RF) signal. The laser in the DM-OEO is modulated by a rectangular wave [...] Read more.

In this study, the oscillation signal stabilization and spurious tone suppression of a directly modulated optoelectronic oscillator (DM-OEO) are simultaneously achieved by modulating a laser with a low-frequency radio frequency (RF) signal. The laser in the DM-OEO is modulated by a rectangular wave with a period inversely proportional to the frequency interval of the spurious tones and a duty cycle of 50%. The optical sidebands of the rectangular wave-modulated laser pulled the optical gain of the spurious tones of the DM-OEO, resulting in a spurious tone suppression and time stabilization in the DM-OEO signal. We achieve a 15 GHz DM-OEO with a 40.14 dB side-mode suppression ratio (SMSR) and 2.55 dB improvement in the oscillation power stability compared to that without RF modulation. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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