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Photonics, Volume 9, Issue 6 (June 2022) – 70 articles

Cover Story (view full-size image): Laser diffraction from periodic structures usually shows an isolated and sharp point-pattern at zeroth and higher orders. Here, we report large-area diffraction zones in the holographic three-dimensional graded photonic super-crystals that can be classified as twisted photonic crystals. They also appear as moiré photonic crystals when there is a strong modulation. The diffraction spots due to fractional orders are merged into diffraction zones. These diffraction-zone patterns not only demonstrate a characterization method for fabricated twisted photonic crystals but also prove the unique optical properties of the coupling of light from zones with 360o azimuthal angles and broad zenith angles. View this paper
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12 pages, 3277 KiB  
Article
Self-Supervised Monocular Depth Estimation Based on Channel Attention
by Bo Tao, Xinbo Chen, Xiliang Tong, Du Jiang and Baojia Chen
Photonics 2022, 9(6), 434; https://doi.org/10.3390/photonics9060434 - 20 Jun 2022
Cited by 4 | Viewed by 1853
Abstract
Scene structure and local details are important factors in producing high-quality depth estimations so as to solve fuzzy artifacts in depth prediction results. We propose a new network structure that combines two channel attention modules in a deep prediction network. The structure perception [...] Read more.
Scene structure and local details are important factors in producing high-quality depth estimations so as to solve fuzzy artifacts in depth prediction results. We propose a new network structure that combines two channel attention modules in a deep prediction network. The structure perception module (spm) uses a frequency channel attention network. We use frequencies from different perspectives to analyze the channel representation as a compression process. This enhances the perception of the scene structure and obtains more feature information. The detail emphasis module (dem) adopts the global attention mechanism. It improves the performance of deep neural networks by reducing irrelevant information and magnifying global interactive representations. Emphasizing important details effectively fuses features at different scales to achieve more accurate and clearer depth predictions. Experiments show that our network produces clearer depth estimations, and our accuracy rate on the KITTI benchmark has improved from 98.1% to 98.3% in the δ < 1.253 metric. Full article
(This article belongs to the Special Issue Optical 3D Sensing Systems)
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13 pages, 4877 KiB  
Article
Simulation Study of Acoustic-Resolution-Based Photoacoustic Microscopy for Imaging Complex Blood Vessel Networks
by Yuan Liu, Chuqi Yuan and Hongyan Zhang
Photonics 2022, 9(6), 433; https://doi.org/10.3390/photonics9060433 - 18 Jun 2022
Cited by 1 | Viewed by 1844
Abstract
The high-quality imaging of vascular networks in biological tissue is significant to accurate cancer diagnosis with acoustic-resolution-based photoacoustic microscopy (AR-PAM). So far, many new back-projection (BP) models have been proposed to improve the image quality of AR-PAM in the off-focal regions. However, many [...] Read more.
The high-quality imaging of vascular networks in biological tissue is significant to accurate cancer diagnosis with acoustic-resolution-based photoacoustic microscopy (AR-PAM). So far, many new back-projection (BP) models have been proposed to improve the image quality of AR-PAM in the off-focal regions. However, many essential arguments are still open regarding the effectiveness of these methods. To settle these remaining questions and explore the potential and adaptability of these BP methods in vascular network imaging, we conducted extensive simulations of a complex vascular network based on a GPU-based data generation framework. Results show that the SAFT-CF algorithm effectively improves the reconstructed image but mainly highlights point targets. In contrast, the STR-BP algorithm can effectively balance the computational cost, signal-to-noise ratio (SNR), and consistency of target intensity for both point and line targets. Results proved that data interpolation for more A-line numbers would not improve the image quality due to information lost. Thus, the detector number in the scan should be sufficiently large. Results also showed that the STR-BP method improved the PSNR of the image by 4.7 to 7.5 dB, which helps the image withstand a noise level of higher than 25%. The proposed simulation framework and the intuitive findings will guide the design of AR-PAM systems and image reconstruction. Full article
(This article belongs to the Special Issue Photoacoustic Imaging for Biomedical Applications)
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18 pages, 7398 KiB  
Article
Low Power FPGA Implementation of a Smart Building Free Space Optical Communication System
by Rehab Ali, Hossameldin Eassa, Hesham H. Aly, Mohamed Abaza and Saleh M. Eisa
Photonics 2022, 9(6), 432; https://doi.org/10.3390/photonics9060432 - 18 Jun 2022
Cited by 4 | Viewed by 2322
Abstract
Free Space Optical (FSO) communication systems have extensively invaded the speed of smart city evolution due to the current surge in demand for wireless communication spots that can match recent challenges due to high technical leaps in smart city evolution. As the number [...] Read more.
Free Space Optical (FSO) communication systems have extensively invaded the speed of smart city evolution due to the current surge in demand for wireless communication spots that can match recent challenges due to high technical leaps in smart city evolution. As the number of users is vastly increasing throughout all networks in the form of machines, devices, and variously distinct objects, FSO is a hugely recommended robust communication system that mitigates a lot of RF disadvantages on the field with no need for licensing, fast rollout time, and low cost. This paper shows an exploit of a Low Power Field Programmable Gate Array (FPGA) based FSO communication system designed for Line of Sight (LOS) Building to Building Communication over a distance of 12 m using a 650 nm Visible Light (VL) red laser source via On-Off Keying (OOK) and higher-level Intensity Modulation (IM)/Pulse Width Modulation (PWM) schemes. The implemented system reached a doubled data rate than OOK of 230 kbps using the IM technique. Traffic monitoring and building security status can be frequently updated between adherent buildings, each scanning its zone real-time conditions and sharing them with the neighboring links. Full article
(This article belongs to the Topic Optical and Optoelectronic Materials and Applications)
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13 pages, 2684 KiB  
Article
Electric Field Sensor Based on High Q Fano Resonance of Nano-Patterned Electro-Optic Materials
by Xiaowei Yin, Fengli Liu, Wentao Qiu, Can Liu, Heyuan Guan and Huihui Lu
Photonics 2022, 9(6), 431; https://doi.org/10.3390/photonics9060431 - 17 Jun 2022
Cited by 3 | Viewed by 2336
Abstract
This paper presents theoretical studies of Fano resonance based electric-field (E-field) sensors. E-field sensor based on two electro-optical (EO) materials i.e., barium titanate (BaTiO3, BTO) nanoparticles and relaxor ferroelectric material Pb(Mg1/3Nb2/3)O3-PbTiO [...] Read more.
This paper presents theoretical studies of Fano resonance based electric-field (E-field) sensors. E-field sensor based on two electro-optical (EO) materials i.e., barium titanate (BaTiO3, BTO) nanoparticles and relaxor ferroelectric material Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) combined with nanostructure are studied. As for the BTO based E-field sensor, a configuration of filling the BTO nanoparticles into a nano-patterned thin film silicon is proposed. The achieved resonance quality factor (Q) is 11,855 and a resonance induced electric field enhancement factor is of around 105. As for the design of PMN-PT based E-field sensor, a configuration by combining two square lattice air holes in PMN-PT thin film but with one offsetting hole left is chosen. The achieved resonance Q is of 9,273 and an electric field enhancement factor is of around 96. The resonance wavelength shift sensitivity of PMN-PT nanostructured can reach up to 4.768 pm/(V/m), while the BTO based nanostructure has a sensitivity of 0.1213 pm/(V/m). If a spectrum analyzer with 0.1 pm resolution is considered, then the minimum detection of the electric field Emin is 20 mV/m and 0.82 V/m for PMN-PT and BTO based nanostructures, respectively. The nano-patterned E-field sensor studied here are all dielectric, it has therefore the advantage of large measurement bandwidth, high measurement fidelity, high spatial resolution and high sensitivity. Full article
(This article belongs to the Special Issue Advances in Photonic Integrated Devices and Circuits)
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12 pages, 4580 KiB  
Article
Laser Self-Mixing Interferometer Based on Multiple Reflections and Phase-Modulation Technique
by Xiulin Wang, Liping Lv, Desheng Zhu, Hanqiao Chen and Wencai Huang
Photonics 2022, 9(6), 430; https://doi.org/10.3390/photonics9060430 - 17 Jun 2022
Cited by 1 | Viewed by 1579
Abstract
An improved method combining multiple reflections with the phase-modulation technique (MR-PM) is proposed to construct a self-mixing interferometer with high accuracy. The phase modulation is performed by using an electro-optic modulator that is placed in the external cavity. To broaden the harmonic components [...] Read more.
An improved method combining multiple reflections with the phase-modulation technique (MR-PM) is proposed to construct a self-mixing interferometer with high accuracy. The phase modulation is performed by using an electro-optic modulator that is placed in the external cavity. To broaden the harmonic components spectrum of the self-mixing signal, the multiple-reflection technique is employed. By extracting orthogonal signals from the spectrum, phase demodulation is implemented to realize displacement reconstruction. The principle and signal processing approach are described in detail. A series of simulations and experiments indicate that the measurement accuracy of the system can be effectively improved with the increase in reflection times. The vibration with an amplitude of 44 nm has been proved to be measurable with a reconstruction error less than 3 nm. Due to the advantages of high accuracy and broad measurement range, the proposed method will play a significant role in the field of non-contact nanometer vibration measurement. Full article
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14 pages, 2805 KiB  
Article
Raman-Guided Bronchoscopy: Feasibility and Detection Depth Studies Using Ex Vivo Lung Tissues and SERS Nanoparticle Tags
by Zongyu Wu, Ziwen Wang, Haoqiang Xie, Yiming Wang, Haoqi He, Shuming Nie, Jian Ye and Li Lin
Photonics 2022, 9(6), 429; https://doi.org/10.3390/photonics9060429 - 17 Jun 2022
Cited by 6 | Viewed by 2688
Abstract
Image-guided and robotic bronchoscopy is currently under intense research and development for a broad range of clinical applications, especially for minimally invasive biopsy and surgery of peripheral pulmonary nodules or lesions that are frequently discovered by CT or MRI scans. Optical imaging and [...] Read more.
Image-guided and robotic bronchoscopy is currently under intense research and development for a broad range of clinical applications, especially for minimally invasive biopsy and surgery of peripheral pulmonary nodules or lesions that are frequently discovered by CT or MRI scans. Optical imaging and spectroscopic modalities at the near-infrared (NIR) window hold great promise for bronchoscopic navigation and guidance because of their high detection sensitivity and molecular/cellular specificity. However, light scattering and background interference are two major factors limiting the depth of tissue penetration of photons, and diseased lesions such as small tumors buried under the tissue surface often cannot be detected. Here we report the use of a miniaturized Raman device that is inserted into one of the bronchoscope channels for sensitive detection of “phantom” tumors using fresh pig lung tissues and surface-enhanced Raman scattering (SERS) nanoparticle tags. The ex vivo results demonstrate not only the feasibility of using Raman spectroscopy for endoscopic guidance, but also show that ultrabright SERS nanoparticles allow detection through a bronchial wall of 0.85 mm in thickness and a 5 mm-thick layer of lung tissue (approaching the fourth-generation airway). This work highlights the prospects and potential of Raman-guided bronchoscopy for minimally invasive imaging and detection of lung lesions. Full article
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14 pages, 2587 KiB  
Article
Spectrum-Entropy-Minimized Routing and Spectrum Allocation in IP over Mixed-Fixed/Flex-Grid Optical Networks
by Xiaosong Yu, Lu Lu, Qingcheng Zhu, Yongli Zhao, Avishek Nag and Jie Zhang
Photonics 2022, 9(6), 428; https://doi.org/10.3390/photonics9060428 - 17 Jun 2022
Viewed by 1553
Abstract
Mixed-Fixed/Flex-Grid Optical Networks (MFGONs) are a new paradigm that emerged during the brown-field migration from fixed-grid Wavelength Division Multiplexing (WDM) optical networks to flex-grid Elastic Optical Networks (EONs). Based on the flex-grid, we can accommodate IP traffic directly to the optical layer by [...] Read more.
Mixed-Fixed/Flex-Grid Optical Networks (MFGONs) are a new paradigm that emerged during the brown-field migration from fixed-grid Wavelength Division Multiplexing (WDM) optical networks to flex-grid Elastic Optical Networks (EONs). Based on the flex-grid, we can accommodate IP traffic directly to the optical layer by configuration. Considering the different granularities of spectrum resources and complex constraints in MFGONs, it is difficult to apply Routing and Wavelength/Spectrum Allocation (RWA/RSA) algorithms proposed in either fixed-grid or flex-grid optical networks. This paper first proposes two concepts, i.e., Link Spectrum Compactness (LSC) and Radiancy of Nodes (RoNs), to evaluate different scenarios of candidate paths for the end-to-end requests in MFGONs. Then, based on these two concepts, a Spectrum Entropy (SE) model is proposed in MFGONs. Here, the SE is the metric that combines LSC and RoNs to judge the fragmentation of network resources, and the value of SE is treated as the cost of candidate paths during the RSA operation. Finally, an SE-minimized RSA algorithm in MFGONs is designed. Simulation results prove that the proposed algorithm can effectively reduce the Bandwidth Blocking Ratio (BBR) and increase the revenues for upgrading the nodes compared to the state-of-the-art RSA algorithm. Particularly, the performance improvement is more obvious for highly connected networks. Full article
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9 pages, 1757 KiB  
Communication
High-Harmonic Generation Using a Single Dielectric Nanostructure
by Seunghwoi Han
Photonics 2022, 9(6), 427; https://doi.org/10.3390/photonics9060427 - 17 Jun 2022
Cited by 2 | Viewed by 1788
Abstract
High-harmonic generation (HHG) from solids is a novel method used to emanate coherent extreme-ultraviolet (EUV) pulses. The efficiency of plasmonic HHG can be improved by enhancing the field of nanostructures. However, the nanostructures used for plasmonic HHG have a limitation owing to the [...] Read more.
High-harmonic generation (HHG) from solids is a novel method used to emanate coherent extreme-ultraviolet (EUV) pulses. The efficiency of plasmonic HHG can be improved by enhancing the field of nanostructures. However, the nanostructures used for plasmonic HHG have a limitation owing to the damage caused by the amplified field. This study presents a single conical sapphire nanostructure used as a compact HHG emitter that generates high-order harmonics with wavelengths up to approximately 60 nm without causing severe damage. We compare the structure with a gold-layered conical sapphire structure and a bulk sapphire. The conical sapphire structure has a higher damage threshold and reusability for EUV generation even though it has a lower HHG intensity than that of the gold-layered conical sapphire structure because of the lower intensity enhancement. The measured signal intensity of the high-order harmonics in the EUV band from the conical sapphire structure is ten times higher than that of the bulk sapphire. The results confirm the possibility of creating a compact EUV light source for nanoscale applications. Full article
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11 pages, 8720 KiB  
Article
Correction of Distorted Wavefront Using Dual Liquid Crystal Spatial Light Modulators
by Jiali Wu, Xizheng Ke, Yaqi Yang, Jingyuan Liang and Mingyu Liu
Photonics 2022, 9(6), 426; https://doi.org/10.3390/photonics9060426 - 17 Jun 2022
Cited by 3 | Viewed by 1822
Abstract
In space optical communication, owing to the influence of atmospheric turbulence, optical beams lose focus and become phase-distorted, which reduces the communication quality. Considering the polarization dependence of liquid crystal spatial light modulators and the dispersion effect of liquid crystal materials, the energy [...] Read more.
In space optical communication, owing to the influence of atmospheric turbulence, optical beams lose focus and become phase-distorted, which reduces the communication quality. Considering the polarization dependence of liquid crystal spatial light modulators and the dispersion effect of liquid crystal materials, the energy utilization rate of liquid crystal adaptive optics systems is low. In this study, a dual liquid crystal spatial light modulator adaptive optics system based on the GS algorithm is used to correct the wavefront distortion of a signal beam under different atmospheric turbulence intensities, and the Strehl ratio (SR) is used as the evaluation index. The simulation results show that the SR of the corrected system can be increased from 0.23, 0.41, and 0.72 to 0.77, 0.89, and 0.95, respectively. The corrected beam spot was more concentrated and the light intensity at the center of the beam spot was stronger. The experimental results show that, after the distortion wavefront is corrected by the dual liquid crystal spatial light modulator, the average gray value of the 10 × 10 pixels in the center of the spot increases from 159.3, 113.1, and 58.4 to 253.4, 247.7, and 198.3, respectively. Full article
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11 pages, 5309 KiB  
Article
Nanoscale Optical Trapping by Means of Dielectric Bowtie
by Giuseppe Brunetti, Nicola Sasanelli, Mario Nicola Armenise and Caterina Ciminelli
Photonics 2022, 9(6), 425; https://doi.org/10.3390/photonics9060425 - 16 Jun 2022
Cited by 16 | Viewed by 2067
Abstract
Plasmonic and dielectric tweezers represent a common paradigm for an innovative and efficient optical trapping at the micro/nanoscale. Plasmonic configurations provide subwavelength mode confinement, resulting in very high optical forces, at the expense of a higher thermal effect, that could undermine the biological [...] Read more.
Plasmonic and dielectric tweezers represent a common paradigm for an innovative and efficient optical trapping at the micro/nanoscale. Plasmonic configurations provide subwavelength mode confinement, resulting in very high optical forces, at the expense of a higher thermal effect, that could undermine the biological sample under test. On the contrary, dielectric configurations show limited optical forces values but overcome the thermal challenge. Achieving efficient optical trapping without affecting the sample temperature is still demanding. Here, we propose the design of a silicon (Si)-based dielectric nanobowtie dimer, made by two tip-to-tip triangle semiconductor elements. The combination of the conservation of the normal component of the electric displacement and the tangential component of the electric field, with a consequent large energy field confinement in the trapping site, ensures optical forces of about 27 fN with a power of 6 mW/µm2. The trapping of a virus with a diameter of 100 nm is demonstrated with numerical simulations, calculating a stability S = 1, and a stiffness k = 0.33 fN/nm, within a footprint of 0.96 µm2, preserving the temperature of the sample (temperature variation of 0.3 K). Full article
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7 pages, 1018 KiB  
Communication
Autofluorescence Imaging of Living Yeast Cells with Deep-Ultraviolet Surface Plasmon Resonance
by Che Nur Hamizah Che Lah, Hirofumi Morisawa, Keita Kobayashi, Atsushi Ono, Wataru Inami and Yoshimasa Kawata
Photonics 2022, 9(6), 424; https://doi.org/10.3390/photonics9060424 - 16 Jun 2022
Cited by 2 | Viewed by 1878
Abstract
Autofluorescence in living cells on aluminum thin film was excited with deep-ultraviolet surface plasmon resonance (deep-UV SPR). Deep-UV SPR under aqueous medium was excited with Kretschmann configuration by using a sapphire prism. Deep-UV SPR is one of the promising techniques for high-sensitive autofluorescence [...] Read more.
Autofluorescence in living cells on aluminum thin film was excited with deep-ultraviolet surface plasmon resonance (deep-UV SPR). Deep-UV SPR under aqueous medium was excited with Kretschmann configuration by using a sapphire prism. Deep-UV SPR is one of the promising techniques for high-sensitive autofluorescence imaging of living cells without staining. Label-free observation is significant for the structural analysis of living cells. We demonstrated the high-sensitive autofluorescence imaging of living yeast cells with deep-UV SPR. We applied a high refractive index prism, such as sapphire, which is suitable for the observation of specimens in aqueous medium, to excite deep-UV SPR. Although typical autofluorescence from living cells is buried in background noise, deep-UV SPR enhances the autofluorescence signal. The deep-UV SPR excitation of an aluminum thin film through a sapphire prism was investigated theoretically and experimentally. It showed that the fluorescence intensities are increased 2.8-fold. Deep-UV SPR enhanced the autofluorescence of cell structures, and yeast cells were found to be very sensitive. As a result, for water-immersed specimens, the sapphire-prism-based Kretschmann configuration excited SPR in deep-UV. Findings from this study suggest that deep-UV SPR can be considered an effective technique for attaining high-sensitivity observation of biological samples. Full article
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14 pages, 1924 KiB  
Review
Ultrafast Fiber Technologies for Compact Laser Wake Field in Medical Application
by Weijian Sha, Jean-Christophe Chanteloup and Gérard Mourou
Photonics 2022, 9(6), 423; https://doi.org/10.3390/photonics9060423 - 16 Jun 2022
Cited by 7 | Viewed by 2868
Abstract
Technologies, performances and maturity of ultrafast fiber lasers and fiber delivery of ultrafast pulses are discussed for the medical deployment of laser-wake-field acceleration (LWFA). The compact ultrafast fiber lasers produce intense laser pulses with flexible hollow-core fiber delivery to facilitate electron acceleration in [...] Read more.
Technologies, performances and maturity of ultrafast fiber lasers and fiber delivery of ultrafast pulses are discussed for the medical deployment of laser-wake-field acceleration (LWFA). The compact ultrafast fiber lasers produce intense laser pulses with flexible hollow-core fiber delivery to facilitate electron acceleration in the laser-stimulated wake field near treatment site, empowering endoscopic LWFA brachytherapy. With coherent beam combination of multiple fiber amplifiers, the advantages of ultrafast fiber lasers are further extended to bring in more capabilities in compact LWFA applications. Full article
(This article belongs to the Special Issue Progress in Laser Accelerator and Future Prospects)
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10 pages, 3992 KiB  
Communication
Experimental Realization of Reconfigurable Photonic Lattices in Coherent Rydberg Atomic Vapors
by Shun Liang, Qingsong Yu, Xing Lei, Shaohuan Ning, Changbiao Li, Yanpeng Zhang and Zhaoyang Zhang
Photonics 2022, 9(6), 422; https://doi.org/10.3390/photonics9060422 - 16 Jun 2022
Cited by 3 | Viewed by 2243
Abstract
We experimentally demonstrated the formation of a one-dimensional electromagnetically induced optical lattice in coherently prepared three-level 85Rb Rydberg atomic vapors with electromagnetically induced transparency (EIT). The one-dimensional photonic lattice was optically induced by a coupling field with a spatially periodical intensity distribution [...] Read more.
We experimentally demonstrated the formation of a one-dimensional electromagnetically induced optical lattice in coherently prepared three-level 85Rb Rydberg atomic vapors with electromagnetically induced transparency (EIT). The one-dimensional photonic lattice was optically induced by a coupling field with a spatially periodical intensity distribution deriving from the interference of two strong Gaussian beams from the same laser source (~480 nm). Under the Rydberg-EIT condition, the incident weak probe beam can feel a tunable spatially modulated susceptibility, which is verified by the controllable discrete diffraction pattern observed at the output plane of the vapor cell. This investigation not only opens the door for experimentally introducing the strong interaction between Rydberg atoms to govern the beam dynamics in photonic lattices based on atomic coherence but also provides an easily accessible periodic environment for exploring Rydberg-atom physics and related applications. Full article
(This article belongs to the Special Issue Optical Quantum Manipulation of Rydberg Atoms)
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13 pages, 7546 KiB  
Article
Refractive Bi-Conic Axicon (Volcone) for Polarization Conversion of Monochromatic Radiation
by Sergey A. Degtyarev, Sergey V. Karpeev, Nikolay A. Ivliev, Yuriy S. Strelkov, Vladimir V. Podlipnov and Svetlana N. Khonina
Photonics 2022, 9(6), 421; https://doi.org/10.3390/photonics9060421 - 16 Jun 2022
Cited by 5 | Viewed by 1689
Abstract
A new element is proposed for producing an azimuthally polarized beam with a vortex phase dependence. The element is formed by two conical surfaces in such a way that the optical element resembles a mountain with a crater on top, like a volcano [...] Read more.
A new element is proposed for producing an azimuthally polarized beam with a vortex phase dependence. The element is formed by two conical surfaces in such a way that the optical element resembles a mountain with a crater on top, like a volcano (volcanic cone is volcone). The element in the form of a refractive bi-conic axicon is fabricated by diamond turning, in which an internal conical cavity is made. Polarization conversion in this optical element occurs on the inner surface due to the refraction of beams at the Brewster angle. The outer surface is used to collimate the converted beam, which significantly distinguishes the proposed element from previously proposed approaches. The paper describes a method for calculating the path of beams through a refractive bi-conic axicon, taking into account phase and polarization conversions. In the case of incident circularly polarized radiation, azimuthally polarized ring-shape beam radiation is generated at the output. The proposed element is experimentally made of polymethyl methacrylate on a CNC milling machine. The experiment demonstrates the effectiveness of the proposed element. Full article
(This article belongs to the Special Issue Polarized Light and Optical Systems)
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18 pages, 2400 KiB  
Review
Can Photobiomodulation Support the Management of Temporomandibular Joint Pain? Molecular Mechanisms and a Systematic Review of Human Clinical Trials
by Jumana Alsarhan, Rita El Feghali, Thaer Alkhudari, Stefano Benedicenti and Claudio Pasquale
Photonics 2022, 9(6), 420; https://doi.org/10.3390/photonics9060420 - 16 Jun 2022
Cited by 3 | Viewed by 2345
Abstract
This study aims to point out the correlation between photobiomodulation (PBM) targets and effects and management of temporomandibular disorders (TMDs) pain using diode lasers with infrared wavelengths ranging from 780 up to 980 nanometers (nm). A systematic search of multiple electronic databases was [...] Read more.
This study aims to point out the correlation between photobiomodulation (PBM) targets and effects and management of temporomandibular disorders (TMDs) pain using diode lasers with infrared wavelengths ranging from 780 up to 980 nanometers (nm). A systematic search of multiple electronic databases was done to identify the clinical trials published between 1st January 2010 and 18th December 2021. The included studies were limited to human subjects who had TMD pain, involving two genders with age > 18 years, and were treated with PBM using a diode laser (780–980 nm) as a non-pharmacological therapy to decrease the intensity of the pain associated to TMDs. The risk of bias for included studies was assessed using the Cochrane RoB tool (for randomized studies). The methodologic quality was rated using the Delphi list. The findings suggest that PBM is an effective tool in alleviating TMDs’ pain and increasing the range of movement in patients with Axis 1 of TMDs. However, TMDs’ pain related to underlying pathology cannot be solely treated by PBM. The causative factors must be treated first. Studies displaying the highest quality Delphi score may represent a suggested PBM therapy protocol to follow for TMDs pain management. Full article
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15 pages, 20304 KiB  
Article
Multiplexed Holographic Combiner with Extended Eye Box Fabricated by Wave Front Printing
by Tobias Wilm, Jens Kibgies, Reinhold Fiess and Wilhelm Stork
Photonics 2022, 9(6), 419; https://doi.org/10.3390/photonics9060419 - 15 Jun 2022
Cited by 4 | Viewed by 2412
Abstract
We present an array-based volume holographic optical element (vHOE) recorded as an optical combiner for novel display applications such as smart glasses. The vHOE performs multiple, complex optical functions in the form of large off-axis to on-axis wave front transformations and an extended [...] Read more.
We present an array-based volume holographic optical element (vHOE) recorded as an optical combiner for novel display applications such as smart glasses. The vHOE performs multiple, complex optical functions in the form of large off-axis to on-axis wave front transformations and an extended eye box implemented in the form of two distinct vertex points with red and green chromatic functions. The holographic combiner is fabricated by our extended immersion-based wave front printing setup, which provides extensive prototyping capabilities due to independent wave front modulation and large possible off-axis recording angles, enabling vHOEs in reflection with a wide range of different recording configurations. The presented vHOE is build up as an array of sub-holograms, where each element is recorded with individual optical functions. We introduce a design and fabrication method to combine two angular and two spectral functions in the volume grating of individual sub-holograms, demonstrating complex holographic elements with four multiplexed optical functions comprised in a single layer of photopolymer film. The introduced design and fabrication process allows the precise tuning of the vHOE’s diffractive properties to achieve well-balanced diffraction efficiencies and angular distributions between individual multiplexed functions. Full article
(This article belongs to the Special Issue Materials, Methods and Models for Holographic Optical Elements)
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12 pages, 3524 KiB  
Article
Control Scheme of Phase-Shifter for Photon Energy Scan
by Gyujin Kim, Haeryong Yang, Chi Hyun Shim, Inhyuk Nam, Myung Hoon Cho, Hoon Heo, Changbum Kim, Chang-Ki Min and Heung-Sik Kang
Photonics 2022, 9(6), 418; https://doi.org/10.3390/photonics9060418 - 15 Jun 2022
Viewed by 1260
Abstract
Variable gap undulator widely used in X-ray free-electron laser (XFEL) enables the photon energy scan by changing its gap. A phase-shifter should be incorporated to compensate for the phase mismatch between the electron bunches and X-ray pulses arising while those traverse the drift [...] Read more.
Variable gap undulator widely used in X-ray free-electron laser (XFEL) enables the photon energy scan by changing its gap. A phase-shifter should be incorporated to compensate for the phase mismatch between the electron bunches and X-ray pulses arising while those traverse the drift space between undulator segments. The uncertainties in both the undulator parameter and the drift space distance introduce an error in calculating the optimum gap distance of the phase-shifter for the different undulator K. The phase-shifter gap needs to be set where the error is within the tolerable range. The control scheme we propose can maintain full FEL intensity over the scanned photon energies. Full article
(This article belongs to the Special Issue XUV and X-ray Free-Electron Lasers and Applications)
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17 pages, 1919 KiB  
Article
A Nonlinear Radio-Photon Conversion Device
by Irina L. Vinogradova, Azat R. Gizatulin, Ivan K. Meshkov, Anton V. Bourdine and Manish Tiwari
Photonics 2022, 9(6), 417; https://doi.org/10.3390/photonics9060417 - 15 Jun 2022
Viewed by 1385
Abstract
The article analyzes existing materials and structures with quadratic-nonlinear optical properties that can be used to generate a difference frequency in the terahertz and sub-terahertz frequency ranges. The principle of constructing a nonlinear optical-radio converter, based on an optical focon (a focusing cone), [...] Read more.
The article analyzes existing materials and structures with quadratic-nonlinear optical properties that can be used to generate a difference frequency in the terahertz and sub-terahertz frequency ranges. The principle of constructing a nonlinear optical-radio converter, based on an optical focon (a focusing cone), is proposed. Based on the assumption that this focon can be implemented from the metal-organic framework (MOF), we propose a technique for modeling its parameters. The mathematical model of the process of propagation and nonlinear interaction of waves inside the focon is based on a simplification of the nonlinear wave equation. Within the framework of the developed model, the following parameters are approximately determined: the 3D gradient of the linear refractive index and the function determining the geometric profile of the focon, which provide a few-mode-based generation of the difference frequency. The achieved theoretical efficiency of radio frequency generation is at least 1%; the proposed device provides a guiding structure for both optical and radio signals in contrast to the known solutions. Full article
(This article belongs to the Special Issue Application of Multimode Optical Fibers)
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11 pages, 1969 KiB  
Article
Calibration of the Soleil–Babinet Compensator Based on the Vectorial Optical Field
by Yayun Ma, Fen Yang and Dong’e Zhao
Photonics 2022, 9(6), 416; https://doi.org/10.3390/photonics9060416 - 15 Jun 2022
Cited by 5 | Viewed by 2094
Abstract
The Soleil–Babinet compensator (SBC) is a variable retarder and has been used in a variety of application fields. A scheme based on the vectorial optical field is proposed to calibrate the SBC by transforming the change of the phase retardation into the visible [...] Read more.
The Soleil–Babinet compensator (SBC) is a variable retarder and has been used in a variety of application fields. A scheme based on the vectorial optical field is proposed to calibrate the SBC by transforming the change of the phase retardation into the visible rotation of the petal-like pattern. The relationship between the rotation angle of the petal-like pattern and the phase retardation of the SBC is established theoretically. In the experiment, the vector beam is generated by using the spiral phase plate (SPP) and the modified Mach–Zehnder interferometer based on the superposition principle of two orthogonal circularly polarized vortex beams with opposite topological charges. Taking advantage of the image processing method, the rotation angles of the acquired petal patterns are calculated, and the relationship between the phase retardation of the SBC and the displacements of its micrometer screw is determined. The measured phase retardation of the SBC ranges from −277.00° to 516.57°. By linearly fitting the experimental data, the phase sensitivity is 33.076 ± 0.147 °/mm, and the coefficient of determination value that shows the linearity of the experimental data is 0.9995. The experimental results agree well with the theoretical data. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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9 pages, 3019 KiB  
Communication
Elimination of Scintillation Noise Caused by External Environment Disturbances in Open Space
by Qi-Xing Tang, Hua Gao, Yu-Jun Zhang and Dong Chen
Photonics 2022, 9(6), 415; https://doi.org/10.3390/photonics9060415 - 15 Jun 2022
Cited by 2 | Viewed by 1227
Abstract
External environment disturbances in open space cause scintillation noise in tunable diode laser absorption spectroscopy (TDLAS), which is used to detect the concentration of gases in air. However, most gases analyzed by TDLAS are present in trace amounts in air. Thus, useful information [...] Read more.
External environment disturbances in open space cause scintillation noise in tunable diode laser absorption spectroscopy (TDLAS), which is used to detect the concentration of gases in air. However, most gases analyzed by TDLAS are present in trace amounts in air. Thus, useful information is typically submerged in strong noise, thereby reducing the detection accuracy. Herein, a method is proposed to eliminate the scintillation noise caused by external environment disturbances in open space. First, the submerged signal is detected via fast coarse-tuning filtering. Then, scintillation noise is eliminated through the extraction and reconstruction of the main feature information. Thereafter, the background signal is obtained by unequal precision. Furthermore, adaptive iterative fitting is performed. Finally, an experimental setup is established for atmospheric detection in an open optical path. The experimental results show that the COD and RSS fitted using the traditional method are 0.87859 and 1.5772 × 10−5, respectively, and those fitted using the proposed method are 0.91448 and 8.81639 × 10−6, respectively. The field results imply that the proposed method has improved accuracy for detecting trace gases in open space and can be employed for practical engineering applications. Full article
(This article belongs to the Special Issue Optical 3D Sensing Systems)
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13 pages, 3346 KiB  
Article
Fast Point Cloud Registration Algorithm Based on 3DNPFH Descriptor
by Bo You, Hongyu Chen, Jiayu Li, Changfeng Li and Hui Chen
Photonics 2022, 9(6), 414; https://doi.org/10.3390/photonics9060414 - 15 Jun 2022
Cited by 5 | Viewed by 2140
Abstract
Although researchers have investigated a variety of approaches to the development of three-dimensional (3D) point cloud matching algorithms, the results have been limited by low accuracy and slow speed when registering large numbers of point cloud data. To address this problem, a new [...] Read more.
Although researchers have investigated a variety of approaches to the development of three-dimensional (3D) point cloud matching algorithms, the results have been limited by low accuracy and slow speed when registering large numbers of point cloud data. To address this problem, a new fast point cloud registration algorithm based on a 3D neighborhood point feature histogram (3DNPFH) descriptor is proposed for fast point cloud registration. With a 3DNPFH, the 3D key-point locations are first transformed into a new 3D coordinate system, and the key points generated from similar 3D surfaces are then close to each other in the newly generated space. Subsequently, a neighborhood point feature histogram (NPFH) was designed to encode neighborhood information by combining the normal vectors, curvature, and distance features of a point cloud, thus forming a 3DNPFH (3D + NPFH). The descriptor searches radially for 3D key point locations in the new 3D coordinate system, reducing the search coordinate system for the corresponding point pairs. The “NPFH” descriptor is then coarsely aligned using the random sample consensus (RANSAC) algorithm. Experiment results show that the algorithm is fast and maintains high alignment accuracy on several popular benchmark datasets, as well as our own data. Full article
(This article belongs to the Special Issue Optical 3D Sensing Systems)
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12 pages, 3575 KiB  
Article
A 60 μm-Long Fiber-to-Chip Edge Coupler Assisted by Subwavelength Grating Structure with Ultralow Loss and Large Bandwidth
by Yan Xiao, Yin Xu, Yue Dong, Bo Zhang and Yi Ni
Photonics 2022, 9(6), 413; https://doi.org/10.3390/photonics9060413 - 12 Jun 2022
Cited by 8 | Viewed by 2844
Abstract
Efficient fiber-to-chip coupling is a key issue in the field of integrated optics and photonics due to the lack of on-chip silicon light source at present. Here, we propose a silicon-based fiber-to-chip edge coupler by use of subwavelength grating (SWG)-assisted structure. The key [...] Read more.
Efficient fiber-to-chip coupling is a key issue in the field of integrated optics and photonics due to the lack of on-chip silicon light source at present. Here, we propose a silicon-based fiber-to-chip edge coupler by use of subwavelength grating (SWG)-assisted structure. The key conversion region is composed of a trident-shaped SWG in the center and two matched strip waveguides on both sides. To achieve high mode match between fiber mode and silicon waveguide mode and to realize low-loss transmission on-chip, we have divided the conversion region into three parts and determined their optimum dimensions. From results, the total device length is only 60 μm from input fiber to output silicon waveguide, and the insertion loss (IL) is as low as 0.23 dB at the wavelength of 1.55 μm. For the working bandwidth, its value can be enlarged to 240 nm (or 390 nm) by keeping IL < 1 dB (or 1.5 dB), which is quite promising for on-chip broadband devices. Based upon these advantages, we hope such a device could be applied in light coupling between optical fiber and on-chip silicon waveguide. Full article
(This article belongs to the Special Issue Silicon Based Integrated Optics)
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11 pages, 3414 KiB  
Article
SNR Enhancement of Direct Absorption Spectroscopy Utilizing an Improved Particle Swarm Algorithm
by Lin Zhang, Yanfang Li, Yubin Wei, Zhaowei Wang, Tingting Zhang, Weihua Gong and Qinduan Zhang
Photonics 2022, 9(6), 412; https://doi.org/10.3390/photonics9060412 - 10 Jun 2022
Cited by 5 | Viewed by 1502
Abstract
A noise elimination method based on an improved particle swarm algorithm is applied to direct absorption spectroscopy. The algorithm combines the theory of spectral line shape to calculate a fitness function according to the original spectra. Comparing the particles and the fitness function [...] Read more.
A noise elimination method based on an improved particle swarm algorithm is applied to direct absorption spectroscopy. The algorithm combines the theory of spectral line shape to calculate a fitness function according to the original spectra. Comparing the particles and the fitness function to calculate the updating direction, and position of particles, the iterative update finally finds the optimal solution. The algorithm is applied to direct absorption spectroscopy to measure methane; compared with the signal without algorithm processing, the signal-to-noise ratio (SNR) is improved by 4.17 times, and the minimum detection limit in the experiment is 15.3 ppb. R2 = 0.9999 is calculated in the calibration experiment, and the error is less than 0.1 ppm in the repeatability experiment of constant methane at 2 ppm concentration. Full article
(This article belongs to the Topic Advance and Applications of Fiber Optic Measurement)
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10 pages, 1716 KiB  
Article
Photonic Bandgaps of One-Dimensional Photonic Crystals Containing Anisotropic Chiral Metamaterials
by Qian Wei, Jiaju Wu, Zhiwei Guo, Xiaotian Xu, Ke Xu, Yong Sun, Yunhui Li, Haitao Jiang and Hong Chen
Photonics 2022, 9(6), 411; https://doi.org/10.3390/photonics9060411 - 10 Jun 2022
Cited by 1 | Viewed by 1745
Abstract
Conventional photonic bandgaps (PBGs) for linear polarization waves strongly depend on the incident angle. Usually, PBGs will shift toward short wavelengths (i.e., blue-shifted gaps) as the incident angle increases, which limits their applications. In some practices, the manipulation of PBGs for circular polarization [...] Read more.
Conventional photonic bandgaps (PBGs) for linear polarization waves strongly depend on the incident angle. Usually, PBGs will shift toward short wavelengths (i.e., blue-shifted gaps) as the incident angle increases, which limits their applications. In some practices, the manipulation of PBGs for circular polarization waves is also important. Here, the manipulation of PBGs for circular polarization waves is theoretically investigated. We propose one-dimensional photonic crystals (1DPCs) containing anisotropic chiral metamaterials which exhibit hyperbolic dispersion for left circular polarization (LCP) wave and elliptical dispersion for right circular polarization (RCP) wave. Based on the phase variation compensation effect between anisotropic chiral metamaterials and dielectrics, we can design arbitrary PBGs including zero-shifted and red-shifted PBGs for LCP wave. However, the PBGs remain blue-shifted for RCP wave. Therefore, we can design a high-efficiency wide-angle polarization selector based on the chiral PBGs. Our work extends the manipulation of PBGs for circular polarization waves, which has a broad range of potential applications, including omnidirectional reflection, splitting wave and enhancing photonic spin Hall effect. Full article
(This article belongs to the Special Issue Photonic Crystals: Physics and Devices)
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9 pages, 2087 KiB  
Communication
Nonlinear Dynamics of Mid-Infrared Interband Cascade Lasers Subject to Variable-Aperture Optical Feedback
by Maorong Zhao, Guangqiong Xia, Ke Yang, Shuman Liu, Junqi Liu, Qiupin Wang, Jianglong Liu and Zhengmao Wu
Photonics 2022, 9(6), 410; https://doi.org/10.3390/photonics9060410 - 10 Jun 2022
Cited by 3 | Viewed by 1738
Abstract
In this work, we experimentally investigate the nonlinear dynamics of an interband cascade laser (ICL) under variable-aperture optical feedback implemented by a gold mirror combining with a ring-actuated iris diaphragm (RAID). By continuously varying the diameter of RAID (DR), the [...] Read more.
In this work, we experimentally investigate the nonlinear dynamics of an interband cascade laser (ICL) under variable-aperture optical feedback implemented by a gold mirror combining with a ring-actuated iris diaphragm (RAID). By continuously varying the diameter of RAID (DR), the evolution of the dynamical state of ICL with the aperture of the optical feedback can be inspected. The characteristics of each dynamical state are characterized by time series, power spectra, phase portraits, and Lyapunov exponents. The results show that, with the decrease of DR, the dynamical state of the ICL under variable-aperture optical feedback presents an evolution from complex, simple to stable. Diverse dynamical states including period one state (P1), period two state (P2), multi-period state (MP), quasi-period state (QP), low-frequency fluctuation (LFF), chaotic state (C), and hyperchaos have been observed. Through mapping the evolution of dynamical states with DR for the ICL biased at different currents, different evolved routes of the dynamical states are revealed. Full article
(This article belongs to the Special Issue Advancements in Semiconductor Lasers)
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10 pages, 9360 KiB  
Communication
An Ultra-Broadband Design of TM-Pass/TE-Stop Polarizer Based on Multistage Bragg Gratings
by Yue Dong, Yu Liu, Yin Xu and Bo Zhang
Photonics 2022, 9(6), 409; https://doi.org/10.3390/photonics9060409 - 10 Jun 2022
Cited by 3 | Viewed by 1368
Abstract
In this paper, a multistage Bragg grating with various kinds of periods is introduced in the design of a reflection-based TM-pass/TE-stop polarizer. The cascade grating sections reflect a wide wavelength range of the TE polarization state. Additionally, on the other hand, the TM [...] Read more.
In this paper, a multistage Bragg grating with various kinds of periods is introduced in the design of a reflection-based TM-pass/TE-stop polarizer. The cascade grating sections reflect a wide wavelength range of the TE polarization state. Additionally, on the other hand, the TM polarization state always passes through the waveguide. Such a design facilitates the polarizer working bandwidth, which is defined as the wavelength range with an extinction ratio of greater than 20 dB, and can reach 231 nm using only three grating sections. Meanwhile, the incision loss is always less than 0.42 dB over the working wavelength band. Furthermore, if a slightly higher loss is permitted, the polarizer working bandwidth can be extended to further than 310 nm using five grating sections. Full article
(This article belongs to the Special Issue Silicon Based Integrated Optics)
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12 pages, 3280 KiB  
Article
The Effect of 5-Aminolevulinic Acid Photodynamic Therapy in Promoting Pyroptosis of HPV-Infected Cells
by Junxiao Wei, Xiaoming Peng, Sijia Wang, Meinian Xu, Hui Liu, Yixiu Zhong, Xi Chen, Qi Wang, Xiaowen Huang and Kang Zeng
Photonics 2022, 9(6), 408; https://doi.org/10.3390/photonics9060408 - 10 Jun 2022
Cited by 2 | Viewed by 1879
Abstract
5-aminolevulinic acid photodynamic therapy (ALA-PDT) is highly effective in the treatment of condyloma acuminata (CA). Previous research has indicated that ALA-PDT could induce cell death by different mechanisms, including apoptosis and autophagy, but the role of pyroptosis in ALA-PDT remains uncertain. Thus, this [...] Read more.
5-aminolevulinic acid photodynamic therapy (ALA-PDT) is highly effective in the treatment of condyloma acuminata (CA). Previous research has indicated that ALA-PDT could induce cell death by different mechanisms, including apoptosis and autophagy, but the role of pyroptosis in ALA-PDT remains uncertain. Thus, this study aimed to explore whether pyroptosis is a potential mechanism of ALA-PDT killing human papillomavirus (HPV) infected cells. HPV-positive HeLa cells were exposed to ALA-PDT, then cell viability assay, lactate dehydrogenase release (LDH) assay, detection of reactive oxygen species (ROS), quantitative real-time PCR (qPCR), and western blot were used to evaluate pyroptosis induced by ALA-PDT. Results suggested that ALA-PDT enhanced the expression of NLRP3, caspase-1, GSDMD, and the production of inflammatory cytokines such as IL-1β and IL-18. In addition, ALA-PDT induced the production of ROS and led to the destruction of the cell membrane. The inhibition of pyroptosis reduced the killing of HeLa cells by ALA-PDT. This study demonstrates that ALA-PDT induces pyroptosis in HPV-positive cells, which provides some explanation for the mechanism of ALA-PDT to treat CA and HPV infection-related diseases. Full article
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14 pages, 5180 KiB  
Article
Geometric Progression of Optical Vortices
by Victor Kotlyar, Alexey Kovalev, Elena Kozlova, Alexandra Savelyeva and Sergey Stafeev
Photonics 2022, 9(6), 407; https://doi.org/10.3390/photonics9060407 - 09 Jun 2022
Cited by 3 | Viewed by 1596
Abstract
We study coaxial superpositions of Gaussian optical vortices described by a geometric progression. The topological charge (TC) is obtained for all variants of such superpositions. The TC can be either integer or half-integer in the initial plane. However, it always remains integer when [...] Read more.
We study coaxial superpositions of Gaussian optical vortices described by a geometric progression. The topological charge (TC) is obtained for all variants of such superpositions. The TC can be either integer or half-integer in the initial plane. However, it always remains integer when the light field propagates in free space. In the general case, the geometric progression of optical vortices (GPOV) has three integer parameters and one real parameter, values which define its TC. The GPOV does not conserve its intensity structure during propagation in free space. However, the beam can have the intensity lobes whose number is equal to one of the family parameters. If the real GPOV parameter is equal to one, then all angular harmonics in the superposition are of the same energy. In this case, the TC of the superposition is equal to the order of the average angular harmonic in the progression. Thus, if the first angular harmonic in the progression has the TC of k and the last harmonic has the TC of n, then the TC of the entire superposition in the initial plane is equal to (n + k)/2, but the TC is equal to n during propagation. The experimental results on generating of the GPOVs by a spatial light modulator are in a good agreement with the simulation results. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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14 pages, 2986 KiB  
Article
Luminescence and Gamma Spectroscopy of Phosphate Glass Doped with Nd3+/Yb3+ and Their Multifunctional Applications
by Bilel Charfi, Kamel Damak, Mohammed S. Alqahtani, Khalid I. Hussein, Ali M. Alshehri, Nehal Elkhoshkhany, Abdullah L. Assiri, Khaled F. Alshehri, Manuela Reben and El Sayed Yousef
Photonics 2022, 9(6), 406; https://doi.org/10.3390/photonics9060406 - 08 Jun 2022
Cited by 6 | Viewed by 1610
Abstract
A new glass with a composition of 40P2O5-30ZnO-20LiCl-10BaF2 (in mol%), doped with 3.5Nd2O3-3.5Yb2O3, was fabricated by the quenching melt technique. The luminescence (PL) and gamma spectroscopy of the glass were [...] Read more.
A new glass with a composition of 40P2O5-30ZnO-20LiCl-10BaF2 (in mol%), doped with 3.5Nd2O3-3.5Yb2O3, was fabricated by the quenching melt technique. The luminescence (PL) and gamma spectroscopy of the glass were investigated systematically. The spectroscopic parameters of the prepared glass, such as the optical energy gap, Judd–Ofelt parameters Ωk (where k = 2, 4 and 6), lifetimes and branching ratio of the Nd3+/Yb3+ level, were evaluated. Moreover, the shielding parameters, such as the linear and mass attenuation coefficients, mean free path and half-value layer, were evaluated. The prepared glass had a spectroscopic quality factor (Ω46) of 0.84, which is about three-times larger than that of the most standard laser host, Nd3+:YAG. The energy of the 2P1/2 (Nd3+) level (~23,250 cm−1) was twice the energy of the Yb3+ transition (~10,290 cm−1). The value of the emission cross section (σem(λ)) of Nd3+:4F3/24I9/2 and Yb3+:2F5/22F7/2 were 2.23 × 10−24 cm2 and 2.88 × 10−24 cm2, respectively. The fabricated glass had a high emission cross section and low mean free path parameters, which makes the fabricated glass a potential candidate for multifunctional applications, such as laser emissions for medical purposes. Full article
(This article belongs to the Special Issue Rare-Earth-Doped Fiber Lasers and Amplifiers)
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17 pages, 5419 KiB  
Article
Drift Artifacts Correction for Laboratory Cone-Beam Nanoscale X-ray Computed Tomography by Fitting the Partial Trajectory of Projection Centroid
by Mengnan Liu, Yu Han, Xiaoqi Xi, Linlin Zhu, Chang Liu, Siyu Tan, Jian Chen, Lei Li and Bin Yan
Photonics 2022, 9(6), 405; https://doi.org/10.3390/photonics9060405 - 08 Jun 2022
Cited by 2 | Viewed by 1913
Abstract
A self-correction method for the drift artifacts of laboratory cone-beam nanoscale X-ray computed tomography (nano-CT) based on the trajectory of projection centroid (TPC) is proposed. This method does not require additional correction phantoms, simplifying the correction process. The whole TPC is estimated by [...] Read more.
A self-correction method for the drift artifacts of laboratory cone-beam nanoscale X-ray computed tomography (nano-CT) based on the trajectory of projection centroid (TPC) is proposed. This method does not require additional correction phantoms, simplifying the correction process. The whole TPC is estimated by the partial TPC in the optimal projection set. The projection drift is calculated by the measured TPC and the estimated TPC. The interval search method is used so that the proposed method can adapt to the case of a truncated projection due to drift. The fixed-angle scanning experiment of the Siemens star and the partial derivative analysis of the projection position show the necessity of correcting drift artifacts. Further, the Shepp–Logan phantoms with different drift levels are simulated. The results show that the proposed method can effectively estimate the horizontal and vertical drifts within the projection drift range of ±2 mm (27 pixels) with high accuracy. Experiments were conducted on tomato seed and bamboo stick to validate the feasibility of the proposed method for samples with different textures. The correction effect on different reconstructed slices indicates that the proposed method provides performance superior to the reference scanning method (RSM) and global fitting. In addition, the proposed method requires no extra scanning, which improves the acquisition efficiency, as well as radiation utilization. Full article
(This article belongs to the Topic Biomedical Photonics)
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