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Photonics
Volume 10
Issue 6
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Photonics, Volume 10, Issue 6 (June 2023) – 98 articles

Cover Story (view full-size image): This concept overcomes the coherence time barrier and results in ultrashort pulses in X-ray Free Electron Lasers. As well as a numerical illustration, the results of the first experimental test at the soft X-ray FEL user facility FLASH are presented. The measured pulse duration approaches 1 fs (FWHM) with pulse energies of 1.5 µJ at a wavelength of 5 nm. The application of the proposed technique to hard X-ray FELs can open the way to generate extremely short pulses, in the range of a few tens of attoseconds. View this paper
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11 pages, 6388 KiB  
Article
The Spatiotemporal Dynamics of Electron Plasma in Femtosecond Laser Double Pulses Induced Damage in Fused Silica
by Tianlun Shen, Jinhai Si, Dongpo Tian, Tao Chen, Peng Li and Xun Hou
Photonics 2023, 10(6), 702; https://doi.org/10.3390/photonics10060702 - 20 Jun 2023
Cited by 2 | Viewed by 1029
Abstract
In this study, we employed the fs time-resolved shadowgraphy method to investigate the impact of the first pump pulse (DP1) on the transient temporal and spatial evolution of electron plasma induced by femtosecond (fs) laser double pulses (DPs) in fused silica. It was [...] Read more.
In this study, we employed the fs time-resolved shadowgraphy method to investigate the impact of the first pump pulse (DP1) on the transient temporal and spatial evolution of electron plasma induced by femtosecond (fs) laser double pulses (DPs) in fused silica. It was observed that the DP1-induced phase transition acted as a waveguide, confining the propagation of the second pump pulse (DP2) light inside the material and resulting in a decrease in the diameter of the DP2-induced electron plasma region. Moreover, the DP2-induced maximum peak electron density was higher than that induced by a single pulse (SP) at the same pulse energy, which may be explained by the DP1-induced highly absorbing semi-metallic state of warm dense glass in fused silica. Importantly, as the energy of DP1 increased, the mean diameter of the DP2-induced electron plasma region further decreased, and the maximum peak electron density increased. Compared with SPs, DPs more easily produced damage in fused silica. In addition, the mean diameter of the DP2-induced electron plasma region and the maximum peak electron density remained almost unchanged when the pulses’ time separation (ts) was changed from 1 to 50 ps, mainly due to the long relaxation time of the phase transition caused by DP1. Full article
(This article belongs to the Special Issue Ultrafast Laser Systems)
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8 pages, 2835 KiB  
Communication
Phase Regeneration of QPSK Signals Based on Kerr Soliton Combs
by Xinjie Han, Yong Geng, Haocheng Ke and Kun Qiu
Photonics 2023, 10(6), 701; https://doi.org/10.3390/photonics10060701 - 20 Jun 2023
Viewed by 856
Abstract
We demonstrate a phase-sensitive and amplification-based all-optical phase regenerator by utilizing on-chip Kerr soliton combs. In the experiment, we demonstrate the direct generation of a Kerr soliton comb in a silicon nitride micro-ring at the receiver side of optical communication systems by applying [...] Read more.
We demonstrate a phase-sensitive and amplification-based all-optical phase regenerator by utilizing on-chip Kerr soliton combs. In the experiment, we demonstrate the direct generation of a Kerr soliton comb in a silicon nitride micro-ring at the receiver side of optical communication systems by applying the transmitted signal as a pump light. The mutual coherence between the signal and the regenerated Kerr comb is excellent, and the all-optical phase regeneration of a 20 GBaud/s QPSK signal is achieved. In contrast to the traditional scheme, our solution shows better SWaP (size, weight, and power) factors. Our study will enhance the relay and reception performance of all-optical communication systems. Full article
(This article belongs to the Special Issue New Trend in Nanophotonics)
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17 pages, 19209 KiB  
Article
Terahertz Bessel Beams Formed by Binary and Holographic Axicons
by Boris Knyazev, Natalya Osintseva, Maxim Komlenok, Vladimir Pavelyev, Vasily Gerasimov, Oleg Kameshkov, Yulia Choporova and Konstantin Tukmakov
Photonics 2023, 10(6), 700; https://doi.org/10.3390/photonics10060700 - 20 Jun 2023
Viewed by 1059
Abstract
The characteristics of high-power vortex Bessel beams in the terahertz range (λ=141 μm) obtained with the use of diffractive axicons (DAs) illuminated by a Gaussian beam of the Novosibirsk free-electron laser were studied. Two of the three possible types of [...] Read more.
The characteristics of high-power vortex Bessel beams in the terahertz range (λ=141 μm) obtained with the use of diffractive axicons (DAs) illuminated by a Gaussian beam of the Novosibirsk free-electron laser were studied. Two of the three possible types of DA recently described in our previous paper, namely, binary spiral silicon axicons (BAs), forming beams with a topological charge l equal to 0–4 and 9, and a diamond “holographic” axicon (HA), forming a beam with l=9, were used in the experiments. These axicons formed beams whose cross sections in the region of inner Bessel rings were close to those of ideal Bessel beams, but their intensities varied in azimuth with a frequency of l and 2l for the BAs and HA, respectively. However, in the case of the BAs, the beams had a pronounced helical structure at the periphery, whereas for the HA, the beam was axisymmetric. By focusing these beams with a lens, we studied the structure of the so-called “perfect” beams (PBs). While an ideal Bessel beam exhibits a PB as a thin ring, in the case of the BAs, we observed a broadened ring structure consisting of 2l short spirals, and for the HA, we observed a narrow ring with 2l maxima in azimuth. A comparison of the numerical calculations and experiments showed that the observed azimuthal intensity variations can be attributed to inaccuracies in the preparation of the axicon relief and/or discrepancies between the calculated and actual wavelengths, within a few percent. The results of this work enable the establishment of quality requirements for axicon manufacture and the appropriate selection of the axicon type in accordance with the requirements for the beam. Full article
(This article belongs to the Special Issue Terahertz Spectroscopy and Imaging)
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15 pages, 4915 KiB  
Article
Properties of Scattering Fields from Gaussian Beam Incident on Rough Cylinders
by Shubing Ye, Guobin Feng, Zhejun Feng, Zhenbao Wang, Dahui Wang and Changqing Cao
Photonics 2023, 10(6), 699; https://doi.org/10.3390/photonics10060699 - 20 Jun 2023
Viewed by 941
Abstract
At present, most researchers focus on plane wave incident on targets, but in practical applications, most of the beams are Gaussian beam. We study the scattering fields of Gaussian beam incident on rough cylinders. Coherent and incoherent scattering coefficients are obtained based on [...] Read more.
At present, most researchers focus on plane wave incident on targets, but in practical applications, most of the beams are Gaussian beam. We study the scattering fields of Gaussian beam incident on rough cylinders. Coherent and incoherent scattering coefficients are obtained based on the angular spectrum expansion and physical optics approximation, and the effects of cylinder roughness, beam radius, cylinder radius and angle of incidence on scattering coefficients are analyzed. The results show that, for a constant wavelength, when the root mean square height is greater than or equal to 1/5 of the wavelength, the coherent scattering coefficient curve undergoes a change in its distribution, with the peak transforming into a trough. Furthermore, when the root mean square height is greater than or equal to 1/3 of the wavelength, the incoherent scattering coefficient experiences a decline as the root mean square height increases. The correlation length only affects the incoherent scattering coefficient. Both the coherent and incoherent scattering coefficients decrease with the increase in the incident angle. Finally, when the roughness and incident angle are constant, with the increase in the ratio of the cylinder radius to the beam waist radius, the scattered light field is more concentrated. Our results provide the theoretical basis for the measurement of the cylindrical scattering field. Full article
(This article belongs to the Special Issue Novel Laser Technologies and Their Applications)
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27 pages, 4048 KiB  
Review
A Concise Review of the Progress in Photonic Sensing Devices
by Muhammad Shahbaz, Muhammad A. Butt and Ryszard Piramidowicz
Photonics 2023, 10(6), 698; https://doi.org/10.3390/photonics10060698 - 20 Jun 2023
Cited by 8 | Viewed by 3129
Abstract
Photonic sensing devices have become increasingly important in various fields such as agriculture, medicine, biochemical sensing, and manufacturing. They are highly sensitive and can classify minor changes in the physical and chemical properties of the ambient medium with high precision. This makes them [...] Read more.
Photonic sensing devices have become increasingly important in various fields such as agriculture, medicine, biochemical sensing, and manufacturing. They are highly sensitive and can classify minor changes in the physical and chemical properties of the ambient medium with high precision. This makes them practical in applications where accurate measurements are critical, such as medical diagnostics and environmental monitoring. In this review paper, recent advances in different types of photonic sensors are discussed, which include photonic crystal-based sensors, surface plasmon resonance-based sensors, optical fiber-based sensors, optical waveguide-based sensors, and wearable sensors. These highly fascinating sensing devices play a crucial role in countless applications and have several advantages over traditional sensors. As technology continues to advance, we can expect photonic sensors to become even more precise, versatile, and reliable. Full article
(This article belongs to the Special Issue Advanced Photonic Sensing and Measurement)
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15 pages, 5696 KiB  
Article
Turn a Shrimp into a Firefly: Monitoring Tissue pH in Small Crustaceans Using an Injectable Hydrogel Sensor with Infrared Excitation and Visible Luminescence
by Anna Nazarova, Anton Gurkov, Yaroslav Rzhechitskiy, Ekaterina Shchapova, Andrei Mutin, Alexandra Saranchina, Anastasiia Diagileva, Nadezhda Bolbat, Pavel Krivoshapkin and Maxim Timofeyev
Photonics 2023, 10(6), 697; https://doi.org/10.3390/photonics10060697 - 20 Jun 2023
Viewed by 1732
Abstract
Various implantable optical sensors are an emerging tool in animal physiology and medicine that may provide real-time information about body fluids without tissue extraction. Such sensors are often fluorescence-based and require strong visible external illumination during signal acquisition, which causes anxiety or even [...] Read more.
Various implantable optical sensors are an emerging tool in animal physiology and medicine that may provide real-time information about body fluids without tissue extraction. Such sensors are often fluorescence-based and require strong visible external illumination during signal acquisition, which causes anxiety or even stress for small animals and thus may influence the physiological parameters being measured. In order to overcome this obstacle, here, we combined a fluorescent molecular pH probe with upconverting particles within a hydrogel fiber suitable for injection into small crustaceans. The green luminescence of the particles under non-visible infrared illumination excited fluorescence of the molecular probe and allowed for pH measurements after correction of the probe readout for luminescence intensity. The developed optical setup based on a common microscope ensured effective visualization of the sensor and spectral pH measurements through the translucent exoskeleton of the amphipod (Amphipoda, Crustacea) Eulimnogammarus verrucosus, endemic to ancient Lake Baikal. Testing the sensors in these cold-loving crustaceans under environmentally relevant temperature increases showed alkalization of amphipod internal media by 0.2 soon after the start of the experiment, while further increases led to acidification by 0.5. The applied approach for simple sensor preparation can be useful in building other implantable optical sensors for light-sensitive organisms. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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19 pages, 4882 KiB  
Article
Joint-Transceiver Equalization Technique over a 1.4 km Multi-Mode Fiber Using Optical MIMO Technique in IM/DD Systems
by Jasmeet Singh and Andreas Ahrens
Photonics 2023, 10(6), 696; https://doi.org/10.3390/photonics10060696 - 19 Jun 2023
Viewed by 1087
Abstract
In optical fiber communication, recent advances in multiple-input and multiple-output (MIMO) systems using space-division multiplexing have helped achieve higher spectral efficiency and data rates. Propagating higher-order modulation formats over MIMO systems further strengthens the capacity of the transmission link. In the optical-MIMO system, [...] Read more.
In optical fiber communication, recent advances in multiple-input and multiple-output (MIMO) systems using space-division multiplexing have helped achieve higher spectral efficiency and data rates. Propagating higher-order modulation formats over MIMO systems further strengthens the capacity of the transmission link. In the optical-MIMO system, the dispersion impairments originating from a 1.4 km long multi-mode fiber (MMF) are mitigated using the proposed joint-transceiver equalization technique. A numerical convex optimization algorithm is used to compute and optimize the pre- and post-equalization (PPE) coefficients jointly restricted by cost and power budgets. The potential of the proposed joint-PPE technique is tested on an MMF link, which is severely degraded by dispersion compared to a single-mode fiber channel. From the experimental results, the average optical received power gain necessary to reach 10−4 bit-error rate is improved by nearly 2.5 dB using the joint-PPE compared to the post-equalization only based on the minimum mean-squared error principle. When the efficiency of the conventional zero-forcing (ZF) principle-based PPE and the joint-PPE is compared, the joint-PPE scheme outperforms the ZF-PPE by approximately 1.5 dB. The enhancement in the transmission quality is observed with experimentally measured eye diagrams using the joint-PPE scheme. Under the analyzed scenarios, computer simulation also confirms the hypothesis, which establishes the effectiveness of the proposed joint-transceiver equalization over the conventional ZF-PPE scheme. Moreover, the simulated performance benefits of the joint-PPE are evaluated using the singular value decomposition (SVD) technique. Improvement of ≈3.86 dB in the average optical received power gain required to reach 10−4 bit-error rate is witnessed with the PAM-4 format. Overall, the joint-transceiver equalization technique is proven to be beneficial in optical MIMO systems. Full article
(This article belongs to the Special Issue Advances in Photoelectric Tracking Systems)
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16 pages, 9976 KiB  
Article
A Polarized Structured Light Method for the 3D Measurement of High-Reflective Surfaces
by Jixin Liang, Yuping Ye, Feifei Gu, Jiankai Zhang, Juan Zhao and Zhan Song
Photonics 2023, 10(6), 695; https://doi.org/10.3390/photonics10060695 - 19 Jun 2023
Cited by 4 | Viewed by 1658
Abstract
The reflection phenomenon exhibited by highly reflective surfaces considerably affects the quality of captured images, thereby rendering the task of structured light (SL) 3D reconstruction. In this paper, a polarized SL method is proposed to address the reconstruction issues on high-reflectance surfaces. The [...] Read more.
The reflection phenomenon exhibited by highly reflective surfaces considerably affects the quality of captured images, thereby rendering the task of structured light (SL) 3D reconstruction. In this paper, a polarized SL method is proposed to address the reconstruction issues on high-reflectance surfaces. The SL system we build in this paper involves a four-channel polarizing camera and a digital light processing (DLP) projector equipped with a polarizer in the lens. The built system enables the simultaneous acquisition of four groups of fringe images, each with different brightness differences. Then, a binary time-multiplexing SL method is adopted to obtain four distinct point clouds. Additionally, a fusion algorithm is proposed to merge the four point clouds into a single, precise, and complete point cloud. Several experiments have been conducted to demonstrate that the proposed method is capable of achieving excellent reconstruction outcomes on highly reflective surfaces. Full article
(This article belongs to the Special Issue Optical Imaging and Measurements)
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13 pages, 2491 KiB  
Communication
Development and Analysis of Multifeature Approaches in SPR Sensor Development
by Arnaldo Leal-Junior, Guilherme Lopes and Carlos Marques
Photonics 2023, 10(6), 694; https://doi.org/10.3390/photonics10060694 - 19 Jun 2023
Cited by 2 | Viewed by 881
Abstract
This paper presents the development and signal analysis of surface plasmon resonance (SPR)-based sensors in D-shaped polymer optical fibers (POFs). A gold-palladium (Au-Pd) coating was applied to the D-shaped region to obtain the SPR signal in the transmitted spectrum of the POFs, where [...] Read more.
This paper presents the development and signal analysis of surface plasmon resonance (SPR)-based sensors in D-shaped polymer optical fibers (POFs). A gold-palladium (Au-Pd) coating was applied to the D-shaped region to obtain the SPR signal in the transmitted spectrum of the POFs, where different samples were fabricated using the same methods and parameters. In this case, the transmitted spectra of three sets of samples were compared, which indicated variations in the SPR signature that can influence the sensors’ application and reproducibility. Then, the intensity of and wavelength shift in the SPR signals were analyzed as a function of the refractive index variation, where it was possible to observe differences in the sensors’ sensitivities and the linearity of the different samples. In this regard, additional features, namely the area below the curve and the peak amplitude of the fast Fourier transform (FFT) applied to the transmitted spectra, were used to enhance the sensors’ accuracy and precision. To verify the use of such additional features in the sensor analysis, an unsupervised approach based on k-means clustering was used considering a single dataset with the results of all the sensors. The results showed clustering with the number of different refractive indices tested, which motivated the use of these features (intensity, wavelength, area and FFT amplitude) in the refractive index assessment. In this context, random forest was the supervised algorithm with the smallest root mean squared error (RMSE) among the algorithms tested, where an RMSE of 0.0057 was obtained considering all the datasets. For the analysis of each sensor (considering the three sets of sensor samples), the mean RMSE using random forest applied to the multifeature approach returned relative errors below 9%, considering the entire tested range of refractive index variation. Full article
(This article belongs to the Special Issue Optical Sensors, Measurements, and Metrology)
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13 pages, 7077 KiB  
Article
Wavelength-Tunable Single-Longitudinal-Mode Narrow-Linewidth Thulium/Holmium Co-Doped Fiber Laser with Phase-Shifted Fiber Bragg Grating and Dual-Coupler-Ring Filter
by Dongyuan Li, Ting Feng, Shaoheng Guo, Shengbao Wu, Fengping Yan, Qi Li and Xiaotian Steve Yao
Photonics 2023, 10(6), 693; https://doi.org/10.3390/photonics10060693 - 19 Jun 2023
Cited by 1 | Viewed by 1181
Abstract
A wavelength-tunable single-longitudinal-mode (SLM) narrow-linewidth thulium/holmium co-doped fiber laser (THDFL) was developed in this study. The lasing wavelength was determined by combining a phase-shifted fiber Bragg grating (PS-FBG) and a uniform FBG (UFBG). SLM oscillation was achieved by incorporating a dual-coupler ring filter [...] Read more.
A wavelength-tunable single-longitudinal-mode (SLM) narrow-linewidth thulium/holmium co-doped fiber laser (THDFL) was developed in this study. The lasing wavelength was determined by combining a phase-shifted fiber Bragg grating (PS-FBG) and a uniform FBG (UFBG). SLM oscillation was achieved by incorporating a dual-coupler ring filter with the PS-FBG. At a pump power of 2.0 W, the THDFL exhibited excellent SLM lasing performance with a stable optical spectrum. It operated at an output wavelength of ~2050 nm with an optical signal-to-noise ratio of >81 dB, an output power fluctuation of 0.15 dB, a linewidth of 8.468 kHz, a relative intensity noise of ≤−140.32 dB/Hz@≥5 MHz, a slope efficiency of 2.15%, and a threshold power of 436 mW. The lasing wavelength tunability was validated experimentally by stretching the PS-FBG and UFBG simultaneously. The proposed THDFL had significant potential for application in many fields, including free-space optical communication, LiDAR, and high-precision spectral measurement. Full article
(This article belongs to the Special Issue Single Frequency Fiber Lasers and Their Applications)
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17 pages, 5849 KiB  
Article
Numerical and Experimental Investigation of Slope Deformation under Stepped Excavation Equipped with Fiber Optic Sensors
by Jia Wang, Wenwen Dong, Wenzhao Yu, Chengcheng Zhang and Honghu Zhu
Photonics 2023, 10(6), 692; https://doi.org/10.3390/photonics10060692 - 17 Jun 2023
Viewed by 894
Abstract
The real-time evaluation of slope stability is a crucial technical issue in foundation excavation and slope construction. However, conventional monitoring methods often fall short of achieving real-time and accurate measurements, which poses challenges to the timely assessment of slope stability. To address this [...] Read more.
The real-time evaluation of slope stability is a crucial technical issue in foundation excavation and slope construction. However, conventional monitoring methods often fall short of achieving real-time and accurate measurements, which poses challenges to the timely assessment of slope stability. To address this problem, laboratory tests and numerical simulations were jointly used to evaluate slope stability in this paper. In numerical simulations, the finite element method (FEM) results clearly illustrate the distribution and evolution of internal strain during slope excavation, and the limit equilibrium method (LEM) calculates changes in the safety factor. In laboratory tests, the fiber Bragg grating (FBG) sensing technology was employed to monitor the internal strain of the slope in real time. The distribution characteristics of the slope internal strain field under the condition of stepped excavation were analyzed, and the feasibility of strain-based evaluation of slope stability was discussed. The measurements with FBG sensing technology agree well with the numerical simulation results, indicating that FBG can effectively monitor soil strain information. Of great significance is that the maximum horizontal strain of the slope is closely related to the safety factor and can be used to evaluate slope stability. Notably, the horizontal soil strain of the slope provides insight into both the formation and evolution of the critical sliding surface during excavation. The combination of numerical simulation and intelligent monitoring technology based on FBG proposed in this paper provides a reference for capturing strain information inside the slope and realizing real-time assessment and critical warning of slope stability. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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13 pages, 3381 KiB  
Article
Rotational Bloch Boundary Conditions and the Finite-Element Implementation in Photonic Devices
by Zhanwen Wang, Jingwei Wang, Lida Liu and Yuntian Chen
Photonics 2023, 10(6), 691; https://doi.org/10.3390/photonics10060691 - 16 Jun 2023
Cited by 1 | Viewed by 911
Abstract
This article described the implementation of rotational Bloch boundary conditions in photonic devices using the finite element method (FEM). For the electromagnetic analysis of periodic structures, FEM and Bloch boundary conditions are now widely used. The vast majority of recent research, however, focused [...] Read more.
This article described the implementation of rotational Bloch boundary conditions in photonic devices using the finite element method (FEM). For the electromagnetic analysis of periodic structures, FEM and Bloch boundary conditions are now widely used. The vast majority of recent research, however, focused on applying Bloch boundary conditions to periodic optical systems with translational symmetry. Our research focused on a flexible numerical method that may be applied to the mode analysis of any photonic device with discrete rotational symmetry. By including the Bloch rotational boundary conditions into FEM, we were able to limit the computational domain to the original one periodic unit, thus enhancing computational speed and decreasing memory consumption. When combined with the finite-element method, rotational Bloch boundary conditions will give a potent tool for the mode analysis of photonic devices with complicated structures and rotational symmetry. In the meantime, the degenerated modes we calculated were consistent with group theory. Overall, this study expands the numerical tools of studying rotational photonic devices, and has useful applications in the study and design of optical fibers, sensors, and other photonic devices. Full article
(This article belongs to the Special Issue Recent Trends in Computational Photonics)
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13 pages, 3420 KiB  
Communication
Optical Sensor Methodology for Measuring Shift, Thickness, Refractive Index and Tilt Angle of Thin Films
by Anton Nalimov, Sergey Stafeev, Victor Kotlyar and Elena Kozlova
Photonics 2023, 10(6), 690; https://doi.org/10.3390/photonics10060690 - 15 Jun 2023
Viewed by 1036
Abstract
We propose a simple optical method and device design for the non-contact determination of small shift, thickness, refractive index, and tilt angle of thin films. The proposed sensor consists of a laser light source, a third- or two-order spiral amplitude zone plate with [...] Read more.
We propose a simple optical method and device design for the non-contact determination of small shift, thickness, refractive index, and tilt angle of thin films. The proposed sensor consists of a laser light source, a third- or two-order spiral amplitude zone plate with a high numerical aperture, and a CCD camera connected to a computer. It is shown that the third-order zone plate transforms the incident Gaussian beam into a three-petal rotating beam. By measuring the rotation angle of the three-petal intensity distribution, one can measure the following: a minimum shift along the optical axis of about 7 nm (the wavelength is 532 nm), a change in the plate thickness by 3 nm, a change in the tilt angle of the plate by 0.1 degrees, and a change in the refractive index by 0.01. Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
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18 pages, 5787 KiB  
Review
Light in Orthodontics: Applications of High-Intensity Lasers, Photobiomodulation, and Antimicrobial Photodymanic Therapies in Daily Practice
by Caroline Maria Gomes Dantas, Carolina Lapaz Vivan, Gladys Cristina Dominguez, Solange Mongelli de Fantini and Patricia Moreira de Freitas
Photonics 2023, 10(6), 689; https://doi.org/10.3390/photonics10060689 - 15 Jun 2023
Cited by 1 | Viewed by 1268
Abstract
Orthodontics is constantly seeking innovation towards mechanical efficiency and better oral-related quality of life during treatment. This narrative review aims to discuss novel scientific reports about light therapies and how they can optimize different stages of orthodontic intervention: before, during, and after treatment. [...] Read more.
Orthodontics is constantly seeking innovation towards mechanical efficiency and better oral-related quality of life during treatment. This narrative review aims to discuss novel scientific reports about light therapies and how they can optimize different stages of orthodontic intervention: before, during, and after treatment. Recurrent conditions that can be treated with laser devices are the removal of carious tissue, dentin hypersensitivity, and temporomandibular disorders. Evidence reveals that laser procedures accelerate health recovery, enabling individuals to initiate orthodontic treatment. Along orthodontic procedure, photobiomodulation therapy, is indicated for analgesia after appliance activations, repair of traumatic ulcers, and acceleration of tooth movement. Moreover, antimicrobial photodynamic therapy is well-indicated for effective decontamination of oral infections such as herpetic lesions and peri-implantitis. Finally, high-intensity lasers are good allies in removing brackets and reconditioning red esthetics. There are many benefits to the use of light sources in the orthodontic routine: simplicity of technique, ease of handling devices, minimal invasiveness, and patient comfort during procedures. It is essential that professionals develop a critical overview of technological advances, offering safe and evidence-based therapies. Recent advances indicate that laser therapies improve patient experiences during orthodontic treatment and minimize the side effects of clinical interventions. Full article
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8 pages, 993 KiB  
Communication
Dynamic Tunable Deflection of Radiation Based on Epsilon-Near-Zero Material
by Lin Cheng, Kun Huang, Yu Wang and Fan Wu
Photonics 2023, 10(6), 688; https://doi.org/10.3390/photonics10060688 - 14 Jun 2023
Viewed by 825
Abstract
Epsilon-near-zero nanoantennas can be used to tune the far-field radiation pattern due to their exceptionally large intensity-dependent refractive index. In this study, we propose a hybrid optical antenna based on indium tin oxide (ITO) to enable optical tuning of the deflection of radiation, [...] Read more.
Epsilon-near-zero nanoantennas can be used to tune the far-field radiation pattern due to their exceptionally large intensity-dependent refractive index. In this study, we propose a hybrid optical antenna based on indium tin oxide (ITO) to enable optical tuning of the deflection of radiation, specifically a hybrid structure antenna of ITO and dielectric material, which makes the deflection angle changes 17∘ as incident intensities increase. Moreover, by employing an array of ITO or hybrid nanodisks, we can enhance the unidirectionality of the radiation pattern, resulting in a needle-like shape with an angular beam width α< 8∘ of the main lobe. The deflection angle of the radiation pattern response with the needle-like lobe paves the way for further studies and applications in beam steering and optical modulation where dynamic control of the nanoantennas is highly desirable. Full article
(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)
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10 pages, 3542 KiB  
Article
Confocal Single-Pixel Imaging
by Cheolwoo Ahn and Jung-Hoon Park
Photonics 2023, 10(6), 687; https://doi.org/10.3390/photonics10060687 - 14 Jun 2023
Viewed by 1144
Abstract
Obtaining depth-selective images requires gating procedures such as spatial, nonlinear, or coherence gating to differentiate light originating from different depths of the volume of interest. Nonlinear gating requires pulsed excitation sources and excitation probes, limiting easy usage. Coherence gating also requires broadband sources [...] Read more.
Obtaining depth-selective images requires gating procedures such as spatial, nonlinear, or coherence gating to differentiate light originating from different depths of the volume of interest. Nonlinear gating requires pulsed excitation sources and excitation probes, limiting easy usage. Coherence gating also requires broadband sources and interferometry requiring specialized stable setups. Spatial gating can be used both for fluorescence and reflection geometry and various light sources and thus has the least requirements on hardware, but still requires the use of a pinhole which makes it difficult to use for photography or widefield imaging schemes. Here, we demonstrate that we can utilize a single digital micromirror device (DMD) to simultaneously function as a dynamic illumination modulator and automatically synchronized dynamic pinhole array to obtain depth-sectioned widefield images. Utilizing the multiplexed measurement advantage of single-pixel imaging, we show that the depth and ballistic light gating of the confocal single pixel imaging scheme can be utilized to obtain images through glare and multiple scattering where conventional widefield imaging fails to recover clear images due to saturation or random scattered noise. Full article
(This article belongs to the Topic Biomedical Photonics)
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16 pages, 9702 KiB  
Article
Method and Installation for Efficient Automatic Defect Inspection of Manufactured Paper Bowls
by Shaoyong Yu, Yang-Han Lee, Cheng-Wen Chen, Peng Gao, Zhigang Xu, Shunyi Chen and Cheng-Fu Yang
Photonics 2023, 10(6), 686; https://doi.org/10.3390/photonics10060686 - 14 Jun 2023
Viewed by 864
Abstract
Various techniques were combined to optimize an optical inspection system designed to automatically inspect defects in manufactured paper bowls. A self-assembled system was utilized to capture images of defects on the bowls. The system employed an image sensor with a multi-pixel array that [...] Read more.
Various techniques were combined to optimize an optical inspection system designed to automatically inspect defects in manufactured paper bowls. A self-assembled system was utilized to capture images of defects on the bowls. The system employed an image sensor with a multi-pixel array that combined a complementary metal-oxide semiconductor and a photo detector. A combined ring light served as the light source, while an infrared (IR) LED matrix panel was used to provide constant IR light to highlight the outer edges of the objects being inspected. The techniques employed in this study to enhance defect inspections on produced paper bowls included Gaussian filtering, Sobel operators, binarization, and connected components. Captured images were processed using these technologies. Once the non-contact inspection system’s machine vision method was completed, defects on the produced paper bowls were inspected using the system developed in this study. Three inspection methods were used in this study: internal inspection, external inspection, and bottom inspection. All three methods were able to inspect surface features of produced paper bowls, including dirt, burrs, holes, and uneven thickness. The results of our study showed that the average time required for machine vision inspections of each paper bowl was significantly less than the time required for manual inspection. Therefore, the investigated machine vision system is an efficient method for inspecting defects in fabricated paper bowls. Full article
(This article belongs to the Special Issue Advanced Photonics Sensors, Sources, Systems and Applications)
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12 pages, 2201 KiB  
Article
Dynamic Microscopic Optical Coherence Tomography as a New Diagnostic Tool for Otitis Media
by Anke Leichtle, Zuzana Penxova, Thorge Kempin, David Leffers, Martin Ahrens, Peter König, Ralf Brinkmann, Gereon Hüttmann, Karl-Ludwig Bruchhage and Hinnerk Schulz-Hildebrandt
Photonics 2023, 10(6), 685; https://doi.org/10.3390/photonics10060685 - 13 Jun 2023
Cited by 1 | Viewed by 1475
Abstract
Hypothesis: Otitis media (OM) can be successfully visualized and diagnosed by dynamic microscopic optical coherence tomography (dmOCT). Background: OM is one of the most common infectious diseases and, according to the WHO, one of the leading health problems with high mortality in developing [...] Read more.
Hypothesis: Otitis media (OM) can be successfully visualized and diagnosed by dynamic microscopic optical coherence tomography (dmOCT). Background: OM is one of the most common infectious diseases and, according to the WHO, one of the leading health problems with high mortality in developing countries. Despite intensive research, the only definitive treatment of therapy-refractory OM for decades has been the surgical removal of inflamed tissue. Thereby, the intra-operative diagnosis is limited to the surgeon’s visual impression. Supportive imaging modalities have been little explored and have not found their way into clinical application. Finding imaging techniques capable of identifying inflamed tissue intraoperatively, therefore, is of significant clinical relevance. Methods: This work investigated a modified version of optical coherence tomography with a microscopic resolution (mOCT) regarding its ability to differentiate between healthy and inflamed tissue. Despite its high resolution, the differentiation of single cells with mOCT is often impossible. A new form of mOCT termed dynamic mOCT (dmOCT) achieves cellular contrast using micro-movements within cells based on their metabolism. It was used in this study to establish correlative measurements with histology. Results: Using dmOCT, images with microscopic resolution were acquired on ex vivo tissue samples of chronic otitis media and cholesteatoma. Imaging with dmOCT allowed the visualization of specific and characteristic cellular and subcellular structures in the cross-sectional images, which can be identified only to a limited extent in native mOCT. Conclusion: We demonstrated for the first time a new marker-free visualization in otitis media based on intracellular motion using dmOCT. Full article
(This article belongs to the Special Issue Optical Diagnostics)
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14 pages, 4656 KiB  
Article
Fine Structure of Optical Vortices in Linearly Polarized Laguerre–Gaussian Beams in Oblique Beams Propagating a Uniaxial Crystal
by Yuriy Egorov and Alexander Rubass
Photonics 2023, 10(6), 684; https://doi.org/10.3390/photonics10060684 - 13 Jun 2023
Cited by 1 | Viewed by 855
Abstract
Traditional ideas about linearly polarized paraxial beam propagation along the optical axis of a uniaxial crystal suggest that at the crystal exit face, after propagation through the polarizer, the beam will form an intensity distribution in the form of a conoscopic pattern. Any [...] Read more.
Traditional ideas about linearly polarized paraxial beam propagation along the optical axis of a uniaxial crystal suggest that at the crystal exit face, after propagation through the polarizer, the beam will form an intensity distribution in the form of a conoscopic pattern. Any violation of axial propagation was considered as a perturbation of the conoscopic pattern and was not taken into account. Nevertheless, this process opens up a wide variety of transformations of polarization singularities caused by weak perturbations. In this article, the behavior of linearly polarized low-order Laguerre–Gauss beams in a uniaxial crystal is considered. The existence of a fine structure of radiation on the output face of a uniaxial crystal and the dependence of this fine structure on the parameters of the crystal and the beam are shown. Full article
(This article belongs to the Special Issue Optical Communication, Sensing and Network)
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2 pages, 152 KiB  
Editorial
Special Issue on Coherent Optical Communications
by Fady I. El-Nahal
Photonics 2023, 10(6), 683; https://doi.org/10.3390/photonics10060683 - 12 Jun 2023
Viewed by 905
Abstract
Coherent optical communications have emerged as a groundbreaking technology, enabling data rates of 100 Gbit/s and beyond [...] Full article
(This article belongs to the Special Issue Coherent Optical Communications)
11 pages, 3306 KiB  
Communication
Axial Resolution Enhancement of Optical Sectioning Structured Illumination Microscopy Based on Three-Beam Interference
by Chao Xiao, Xing Li, Jia Qian, Wang Ma, Junwei Min, Peng Gao, Dan Dan and Baoli Yao
Photonics 2023, 10(6), 682; https://doi.org/10.3390/photonics10060682 - 12 Jun 2023
Cited by 1 | Viewed by 1301
Abstract
As a branch of 3D microscopy, optical sectioning structured illumination microscopy (OS-SIM) has the advantages of fast imaging speed, weak photobleaching and phototoxicity, and flexible and compatible configuration. Although the method of using the one-dimensional periodic fringe pattern projected on the sample can [...] Read more.
As a branch of 3D microscopy, optical sectioning structured illumination microscopy (OS-SIM) has the advantages of fast imaging speed, weak photobleaching and phototoxicity, and flexible and compatible configuration. Although the method of using the one-dimensional periodic fringe pattern projected on the sample can remove the out-of-focus background from the in-focus signal, the axial resolution of the final reconstructed 3D image is not improved. Here, we propose a three-beam interference OS-SIM, namely TBOS, instead of the common-used dual-beam interference OS-SIM (DBOS). The three-beam interference scheme has been adopted in 3D super-resolution SIM (3D-SR-SIM), where the fringe phase shifting needs to be along each of the three orientations. In contrast, TBOS applies phase shifting only in one arbitrary direction. We built a TBOS SIM microscope and performed the 3D imaging experiments with 46 nm diameter fluorescent microspheres and a mouse kidney section. The axial resolution of the 3D image obtained with TBOS was enhanced by a factor of 1.36 compared to the DBOS method, consistent with the theoretical analysis and simulation. The OS-SIM with enhanced axial resolution for 3D imaging may find a wide range of applications in the biomedical field. Full article
(This article belongs to the Special Issue Technologies and Applications of Biophotonics)
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11 pages, 1882 KiB  
Article
The Role of the Photon Counting Loss Effect in Time-Resolved Measurements of Fluorescence Anisotropy
by Daniil A. Gvozdev, Alexey N. Semenov, Georgy V. Tsoraev and Eugene G. Maksimov
Photonics 2023, 10(6), 681; https://doi.org/10.3390/photonics10060681 - 12 Jun 2023
Viewed by 719
Abstract
Determining the rate of rotation of molecules from their fluorescence anisotropy decay curves is a powerful method for studying molecular systems in biological applications. The single photon count detection systems used for this have a nonlinear dependence of the photon counting rate on [...] Read more.
Determining the rate of rotation of molecules from their fluorescence anisotropy decay curves is a powerful method for studying molecular systems in biological applications. The single photon count detection systems used for this have a nonlinear dependence of the photon counting rate on the fluorescence intensity flux (photon counting loss effect), which can lead to a number of artifacts. Using metal complexes of phthalocyanines as a test sample, we have shown that such a nonlinearity can cause distortions in the determination of the fluorescence anisotropy lifetime and the asymptotic fluorescence anisotropy. We also assessed the dependence of the described phenomena on temperature and estimated the manifestations of the photon counting loss effect in the case of photobleaching of the fluorophores. Full article
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8 pages, 4410 KiB  
Communication
Research on the Thermal Effect of Micro-Channel Cooled Thin-Slab Tm:YAP Lasers
by Jianhua Shang, Xiaojin Cheng, Qixin Li and Xiangnan Wu
Photonics 2023, 10(6), 680; https://doi.org/10.3390/photonics10060680 - 12 Jun 2023
Viewed by 732
Abstract
Using the finite element method and the heat conduction equation, the temperature, stress, and end-face deformation in Tm:YAP crystal under high pump power were analyzed. Combined with gradient doping technology, an effective way to improve the internal heat distribution of the crystal was [...] Read more.
Using the finite element method and the heat conduction equation, the temperature, stress, and end-face deformation in Tm:YAP crystal under high pump power were analyzed. Combined with gradient doping technology, an effective way to improve the internal heat distribution of the crystal was studied. The results showed that when the total pump power was 200 W, under the same cooling conditions, the maximum temperature difference inside Tm:YAP decreased from 58 K to 25 K after gradient doping. The thermal stress and end-face thermal deformation were also significantly improved. In addition, a reasonable micro-channel structure also effectively removed the heat generated inside the crystal. Full article
(This article belongs to the Special Issue High Power Laser: Theory and Applications)
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7 pages, 1304 KiB  
Communication
Distributed Bragg Reflector Laser Based on Composite Fiber Heavily Doped with Erbium Ions
by Mikhail I. Skvortsov, Kseniya V. Proskurina, Evgeniy V. Golikov, Alexander V. Dostovalov, Vadim S. Terentyev, Olga N. Egorova, Sergey L. Semjonov and Sergey A. Babin
Photonics 2023, 10(6), 679; https://doi.org/10.3390/photonics10060679 - 12 Jun 2023
Cited by 2 | Viewed by 1135
Abstract
A distributed Bragg reflector (DBR) laser with a specially designed, heavily Er3+-doped composite fiber of a length as short as 1.8 cm is demonstrated. The DBR laser, pumped by a 980 nm laser diode with power of up to 370 mW, [...] Read more.
A distributed Bragg reflector (DBR) laser with a specially designed, heavily Er3+-doped composite fiber of a length as short as 1.8 cm is demonstrated. The DBR laser, pumped by a 980 nm laser diode with power of up to 370 mW, generates single-frequency radiation at a wavelength of 1535 nm with a narrow instantaneous linewidth of <100 Hz and a high output power of 2 mW. The obtained Er3+-doped fiber laser parameters pave the way toward a broad range of practical applications from telecommunications and sensing to scientific research. Full article
(This article belongs to the Special Issue Fiber Laser and Their Applications)
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13 pages, 2898 KiB  
Article
Study of the Interference Color with Nomarski Prism Wedge Angle in a Differential Interference Contrast Microscopy System
by Fei Li and Tingyu Zhao
Photonics 2023, 10(6), 678; https://doi.org/10.3390/photonics10060678 - 11 Jun 2023
Viewed by 1289
Abstract
Differential interference contrast microscopy systems demonstrate the phase (optical path) rather than the amplitude of a sample. Previous studies have usually approximated the optical path difference produced by the Normarski prism. We derive the mathematical expression for the optical path difference produced by [...] Read more.
Differential interference contrast microscopy systems demonstrate the phase (optical path) rather than the amplitude of a sample. Previous studies have usually approximated the optical path difference produced by the Normarski prism. We derive the mathematical expression for the optical path difference produced by the incident light at any position of the Nomarski prism. As a result, the optical path difference introduced by the differential interference contrast microscope can be calculated. Moreover, the optical path difference is linearly related to the position of the incident light. In addition, the differential interference contrast microscopy system uses a composite light source, while previous studies were basically performed at a single wavelength. The standard wavelengths d (656 nm), F (587 nm), and C (486 nm) are taken as examples to analyze the relationship between the interference color change of the observation surface under the superposition of different wavelengths and the prism wedge angle when the prism moves. When the prism moves the same distance, the larger the prism wedge Angle is, the faster the interference color change is. The analysis based on practical considerations in this paper is believed to provide a method for studying Nomarski prisms. Full article
(This article belongs to the Special Issue Coherent and Polarization Optics)
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15 pages, 10612 KiB  
Article
Range-Gated LIDAR Utilizing a LiNbO3 (LN) Crystal as an Optical Switch
by Chenglong Luan, Yingchun Li, Huichao Guo and Houpeng Sun
Photonics 2023, 10(6), 677; https://doi.org/10.3390/photonics10060677 - 11 Jun 2023
Cited by 1 | Viewed by 1010
Abstract
In this paper, a range-gated LIDAR system utilizing an LN crystal as the electro-optical switch and a SCMOS (scientific complementary metal oxide semiconductor) imaging device is designed. To achieve range-gated operations, we utilize two polarizers and an LN (LiNbO3) crystal to form an [...] Read more.
In this paper, a range-gated LIDAR system utilizing an LN crystal as the electro-optical switch and a SCMOS (scientific complementary metal oxide semiconductor) imaging device is designed. To achieve range-gated operations, we utilize two polarizers and an LN (LiNbO3) crystal to form an electro-optical switch. The optical switch is realized by applying a pulse voltage at both ends of the crystal due to the crystal’s conoscopic interference effect and electro-optical effect. The advantage of this system is that low-bandwidth detectors, such as a CMOS and a CCD (charge-coupled device), can be used to replace conventional high-bandwidth detectors, such as an ICCD (intensified charge-coupled device), and it displays better imaging performance under specific conditions at the same time. However, after using an electro-optical crystal as an optical switch, a new inhomogeneity error will be introduced due to the conoscopic interference effect of the electro-optical crystal, resulting in a range error for the LIDAR system. To reduce the influence of inhomogeneity error on the system, this paper analyzes the sources of inhomogeneity error caused by the electro-optical crystal and calculates the crystal’s inhomogeneity mathematical expression. A compensation method is proposed based on the above inhomogeneity mathematical expression. An experimental LIDAR system is constructed in this paper to verify the validity of the compensation method. The experimental results of the range-gated LIDAR system show that in a specific field of view (2.6 mrad), the LIDAR system has good imaging performance; its ranging standard deviation is 3.86 cm and further decreases to 2.86 cm after compensation, which verifies the accuracy of the compensation method. Full article
(This article belongs to the Special Issue Laser as a Detection: From Spectral Imaging to LiDAR for Remote Sensing Applications)
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9 pages, 3104 KiB  
Communication
SNR Model of Optical Fiber Acoustic Sensing System Based on F-P Structure
by Yingjie Liu, Chenggang Guan, Yala Tong, Wenxiu Chu, Ruling Zhou and Yikai Zhou
Photonics 2023, 10(6), 676; https://doi.org/10.3390/photonics10060676 - 11 Jun 2023
Cited by 2 | Viewed by 1081
Abstract
The signal-to-noise ratio (SNR) is a crucial parameter for assessing audio transmission quality and fiber optic acoustic sensors. This study presents a model for predicting the SNR of a fiber optic F-P acoustic sensing system using the Fabry–Perot (F-P) cavity length modulation principle, [...] Read more.
The signal-to-noise ratio (SNR) is a crucial parameter for assessing audio transmission quality and fiber optic acoustic sensors. This study presents a model for predicting the SNR of a fiber optic F-P acoustic sensing system using the Fabry–Perot (F-P) cavity length modulation principle, considering noise and line loss in the optical path. To validate the model, we constructed an F-P acoustic sensor system and measured the SNR in a semi-anechoic room. Additionally, we used MATLAB to simulate the SNR model and compared the results with experimental data. The model accurately predicted the SNR of the fiber optic F-P acoustic sensor system. Our results offer valuable guidance and theoretical support for optimizing system performance. Full article
(This article belongs to the Topic Fiber Optic Communication)
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12 pages, 6966 KiB  
Communication
A Terahertz Radiation Linear Polarizer Based on Using a Magnetic Fluid in an External Magnetic Field
by Alexey P. Votintsev, Alexey V. Borisov, Zakhar S. Kochnev, Igor Meglinski and Yury V. Kistenev
Photonics 2023, 10(6), 675; https://doi.org/10.3390/photonics10060675 - 11 Jun 2023
Viewed by 1152
Abstract
A model of a magnetically controlled linear polarizer of terahertz (THz) waves based on a cell filled with a magnetic fluid and controlled by an external magnetic field was proposed. The magnetic fluid consisted of a synthetic oil with high transparency in the [...] Read more.
A model of a magnetically controlled linear polarizer of terahertz (THz) waves based on a cell filled with a magnetic fluid and controlled by an external magnetic field was proposed. The magnetic fluid consisted of a synthetic oil with high transparency in the THz range and ferromagnetic alloy microparticles. Selection of the ferromagnetic particles size and concentration, and also parameters of the external magnetic field was conducted. It was shown that when using ferromagnetic particles of 10–35 μm size, a concentration of 10 wt.%, and a magnetic field with induction of 6.7–57.2 mT, the created construction works as a linear polarizer of the THz wave in the ranged from 0.3 to 1.5 THz, with the degree of polarization of the initially non-polarized THz wave transmitted through the cell being at least of 80%. Full article
(This article belongs to the Special Issue Polarization Optics in Biomedical Applications)
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13 pages, 6515 KiB  
Article
Research on VMD-Based Adaptive TDLAS Signal Denoising Method
by Minghui Mao, Jun Chang, Jiachen Sun, Shan Lin and Zihan Wang
Photonics 2023, 10(6), 674; https://doi.org/10.3390/photonics10060674 - 11 Jun 2023
Cited by 4 | Viewed by 1248
Abstract
We propose an adaptive algorithm that is a Variational Mode Decomposition (VMD) optimized by the particle swarm optimization (PSO) algorithm, named PSO-VMD. The method selects the envelope entropy of the last intrinsic mode function (IMF) in the VMD as the fitness function of [...] Read more.
We propose an adaptive algorithm that is a Variational Mode Decomposition (VMD) optimized by the particle swarm optimization (PSO) algorithm, named PSO-VMD. The method selects the envelope entropy of the last intrinsic mode function (IMF) in the VMD as the fitness function of the PSO and 1/10 of the maximum value of the correlation coefficient between the IMFs and the standard signal as the threshold of the correlation coefficient. In the processing of simulated and experimental second harmonic signals, a series of standards, including the same correlation coefficient threshold and standard signal, are used to adaptively achieve noise reduction processing. After processing a simulated signal using PSO-VMD, the signal-to-noise ratio (SNR) was improved by 4.03877 dB and the correlation coefficient (R2) between the gas concentration and the second harmonic maximum was improved from 0.97743 to 0.99782. In the processing of an experimental signal, the correlation coefficient (R2) was 0.99733. The mean value and standard deviation of the second harmonic signal of multiple cycles processed by PSO-VMD were improved compared to the unprocessed experimental signal. This demonstrated that the method has the advantage of being reliable and stable. Full article
(This article belongs to the Special Issue Applications of Laser Spectroscopy)
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14 pages, 4818 KiB  
Communication
Arbitrary Time Shaping of Broadband Low-Coherence Light Based on Optical Parametric Amplification
by Yue Wang, Xiaochao Wang, Meizhi Sun, Xiao Liang, Hui Wei and Wei Fan
Photonics 2023, 10(6), 673; https://doi.org/10.3390/photonics10060673 - 09 Jun 2023
Cited by 1 | Viewed by 914
Abstract
Laser–plasma interactions (LPIs) hinder the interaction of high-energy laser pulses with targets. The use of broadband low-coherence light has been proposed to reduce the impact of LPIs. In this study, to improve the time–frequency characteristics of broadband low-coherence optical seeds, we proposed an [...] Read more.
Laser–plasma interactions (LPIs) hinder the interaction of high-energy laser pulses with targets. The use of broadband low-coherence light has been proposed to reduce the impact of LPIs. In this study, to improve the time–frequency characteristics of broadband low-coherence optical seeds, we proposed an arbitrary time-shaping technique scheme based on optical parametric amplification (OPA) that differs from traditional arbitrary time shaping. The shaping process and output characteristics were analyzed in detail. The theoretical and experimental results show that an arbitrary time-shaping pulse output with a large time-shaping contrast, fast-rising edge, and wide spectral width can be obtained. The time shaping contrast of the shaped pulse can be >300:1, and the spectral width is ~40 nm. The output time waveform is smoother than in traditional schemes, and the noise-like modulation is approximately 4% (approximately equal to the unshaped initial amplified spontaneous emission source). The arbitrary time-shaping scheme based on OPA provides a viable solution for the temporal waveform shaping of broadband low-coherence light. Full article
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