Research

17 pages, 9244 KiB

Open AccessArticle

High-Precision Manufacture and Alignment of Image Slicer Based on Thin Glass Bonding

by Peng Chen, Jingjing Xia, Jun Yu, Kexin Li, Zhengxiang Shen and Zhanshan Wang

Appl. Sci. 2023, 13(22), 12170; https://doi.org/10.3390/app132212170 - 09 Nov 2023

Viewed by 552

Integral field spectroscopy (IFS) is capable of simultaneously collecting two-dimensional high-resolution spatial image information and spectral information in a target field of view (FOV). The image slicer is the key element in IFS for segmenting the target FOV. Current micro-image slicer fabrication methods [...] Read more.

Integral field spectroscopy (IFS) is capable of simultaneously collecting two-dimensional high-resolution spatial image information and spectral information in a target field of view (FOV). The image slicer is the key element in IFS for segmenting the target FOV. Current micro-image slicer fabrication methods such as molecular assembling need strictly accurate control during sticking, which is time-consuming and expensive. In this study, we improved a direct-adhesive method for thin glass slicer manufacture and alignment. Thin glass is fabricated via single polishing and direct stitching to form a micro-image slicer. Based on charge coupled device (CCD) camera tests on parallel light, the manufacture accuracy for a six-channel image slicer reaches that of the molecular assembling scheme. This method can be applied to the fabrication of image slicers with different apertures. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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12 pages, 4507 KiB

Open AccessArticle

A Calibration Method for Time Dimension and Space Dimension of Streak Tube Imaging Lidar

by Zhaodong Chen, Fangfang Shao, Zhigang Fan, Xing Wang, Chaowei Dong, Zhiwei Dong, Rongwei Fan and Deying Chen

Appl. Sci. 2023, 13(18), 10042; https://doi.org/10.3390/app131810042 - 06 Sep 2023

Viewed by 717

Abstract

Owing to the special working systems of streak tube imaging lidar (STIL), the time and space dimensions are coupled together on the streak images. This coupling can cause measurement errors in 3D point clouds and can make measurement results more complicated to calibrate [...] Read more.

Owing to the special working systems of streak tube imaging lidar (STIL), the time and space dimensions are coupled together on the streak images. This coupling can cause measurement errors in 3D point clouds and can make measurement results more complicated to calibrate than other kinds of lidars. This paper presents a method to generate a time calibration array and an angle calibration array to separate the offset of the streak into time dimension and space dimension. The time and space information of the signal at any position on the streak image can be indexed through these two arrays. A validation experiment on aircraft was carried out, and the range error of the 3D point cloud was improved from 0.41 m to 0.27 m using the proposed calibration method. Thus, using the proposed calibration method can improve the accuracy of the point cloud produced by STIL. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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12 pages, 2413 KiB

Open AccessArticle

Controlling the Spin Hall Effect in the Sharp Focus of an Axial Superposition of Two Optical Vortices with Left- and Right-Handed Circular Polarization

by Victor V. Kotlyar, Anton G. Nalimov and Alexey A. Kovalev

Appl. Sci. 2023, 13(14), 8466; https://doi.org/10.3390/app13148466 - 21 Jul 2023

Viewed by 724

Abstract

We consider sharp focusing of an axial superposition of two optical vortices with identical topological charges, but different amplitudes and circular polarizations of different signs. The ratio of the amplitudes of the two beams is a parameter. When this parameter changes, the polarization [...] Read more.

We consider sharp focusing of an axial superposition of two optical vortices with identical topological charges, but different amplitudes and circular polarizations of different signs. The ratio of the amplitudes of the two beams is a parameter. When this parameter changes, the polarization state of the superposition changes from linear polarization to right-hand circular polarization. Based on the Richards–Wolf theory, exact expressions are obtained for the longitudinal components of the spin angular momentum (SAM) density and orbital angular momentum (OAM) density at the focus of the considered superposition. It follows from these expressions that the sum of the total longitudinal components of the SAM and OAM is conserved upon focusing, and also that, due to the spin-orbit conversion, the total longitudinal component of the SAM decreases during focusing, while the total longitudinal component of the OAM increases by the same amount. By changing the ratio of the amplitudes of the constituent beams from 1 to 0, one can change the value of the spin-orbit conversion from zero (for linear polarization) to a maximum (for circular polarization). Also, by changing this parameter, one can control the spin Hall effect at the focus, which takes place at the focus of the considered beam. This study can be applied for controlling the rotation velocity of microparticles trapped in the focus. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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12 pages, 1750 KiB

Open AccessArticle

Optical Autocorrelation Measurement for Ultrafast Pulses at NIR Wavelengths Using GaP, GaAsP, and Si Photoconductive Detectors

by Hyung-Sik Kim and Yong-Sik Lim

Appl. Sci. 2023, 13(12), 6957; https://doi.org/10.3390/app13126957 - 08 Jun 2023

Viewed by 945

Abstract

In this article, we report on an optical real-time autocorrelator readout with a 5 Hz refresh rate, equipped with a transimpedance amplified photodetector based on the two-photon absorption (TPA) of semiconductor photodiodes (PDs) for ultrashort (1 < ps) pulse measurement. By replacing the [...] Read more.

In this article, we report on an optical real-time autocorrelator readout with a 5 Hz refresh rate, equipped with a transimpedance amplified photodetector based on the two-photon absorption (TPA) of semiconductor photodiodes (PDs) for ultrashort (1 < ps) pulse measurement. By replacing the GaP PD of a commercial TPA detector with GaAsP and Si PD elements, we demonstrated that the spectral response based on the TPA of each photodetector followed the linear response of the corresponding semiconductor PD within accessible wavelength regions. The TPA spectral response of the GaAsP detector exhibited a peak at 1200 nm and a long wavelength limit near 1300 nm. The TPA spectral response of the Si detector exhibited a short wavelength limit near 1170 nm and a linear response up to 1300 nm. The two types of PD were compared with the characteristics of the GaP photodiode. These photoconductive detectors are efficient, compact, and robust sensors and can be used to diagnose the pulse characteristics of ultrafast fiber lasers and light sources near IR wavelengths. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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12 pages, 1391 KiB

Open AccessArticle

Parameter Extraction of Solar Photovoltaic Model Based on Nutcracker Optimization Algorithm

by Zhenjiang Duan, Hui Yu, Qi Zhang and Li Tian

Appl. Sci. 2023, 13(11), 6710; https://doi.org/10.3390/app13116710 - 31 May 2023

Cited by 6 | Viewed by 1410

Abstract

In order to improve the accuracy and reliability of the photovoltaic (PV) model, this paper explores a novel nature-inspired metaheuristic algorithm, i.e., the nutcracker optimizer algorithm (NOA), for the parameter extraction of a PV model, such as a single diode model (SDM), double [...] Read more.

In order to improve the accuracy and reliability of the photovoltaic (PV) model, this paper explores a novel nature-inspired metaheuristic algorithm, i.e., the nutcracker optimizer algorithm (NOA), for the parameter extraction of a PV model, such as a single diode model (SDM), double diode model (DDM), and triple diode model (TDM) of PV components. The Aleo Solar S79Y300 monocrystalline silicon solar panel was tested at 1000 W/m² solar irradiance and 25 °C temperature, and the results of the proposed NOA algorithm were compared with three popular algorithms, i.e., particle swarm optimization (PSO), firework algorithm (FWA), and whale optimization algorithm (WOA), in terms of algorithm accuracy and running time, and non-parametric tests were performed. The results show that the NOA can improve the efficiency of PV parameter extraction, and its performance is the best among the tested algorithms. It has the best root mean square error (RMSE) values in the SDM, being 7.92587 × 10⁻⁵ and 6.02460 × 10⁻⁵ in the DDM and 6.23617 × 10⁻⁵ in the TDM, and the shortest average execution time according to the overall ranking, making it well suited for extracting PV model parameters. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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12 pages, 4347 KiB

Open AccessArticle

Yb-Doped All-Fiber Amplifier with Low-Intensity Noise in mHz Range Oriented to Space-Borne Gravitational Wave Detection

by Zaiyuan Wang, Jiehao Wang, Fan Li, Yuhang Li, Long Tian and Qiang Liu

Appl. Sci. 2023, 13(10), 6338; https://doi.org/10.3390/app13106338 - 22 May 2023

Cited by 1 | Viewed by 1068

Abstract

We present a low-intensity noise single-frequency Yb-doped all-fiber amplifier oriented to space-borne gravitational wave detection. Relative intensity noise (RIN) below −70 dBc/Hz @ 1 mHz~1 Hz was achieved by virtue of feedback-loop-based intensity noise suppression. Based on systematic noise analysis and experimental investigation, [...] Read more.

We present a low-intensity noise single-frequency Yb-doped all-fiber amplifier oriented to space-borne gravitational wave detection. Relative intensity noise (RIN) below −70 dBc/Hz @ 1 mHz~1 Hz was achieved by virtue of feedback-loop-based intensity noise suppression. Based on systematic noise analysis and experimental investigation, we found that the pump noise and temperature-dependent noise of the fiber splitter and the photodetector contributed mainly to the RIN of the fiber amplifier. Therefore, we carefully designed a feedback-loop-based Yb-doped all-fiber amplifier, and finely stabilized the temperature of the pump diode, fiber splitters, and photodetectors. Consequently, the RIN can be suppressed down to −72.5 dBc/Hz around 1 mHz. This low-intensity all-fiber Yb-doped amplifier can be used for space-borne gravitational-wave detection. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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11 pages, 31174 KiB

Open AccessArticle

Influence of Pre-Radiation and Photo-Bleaching on the Yb-Doped Fiber Laser Radiated with Gamma-ray

by Xuefeng Wang, Shihao Sun, Ye Zheng, Miao Yu, Siyuan Li, Yi Cao and Junlong Wang

Appl. Sci. 2023, 13(10), 6146; https://doi.org/10.3390/app13106146 - 18 May 2023

Cited by 2 | Viewed by 991

Abstract

To improve the radiation resistance of Yb-doped fiber lasers, we investigate the influence of pre-radiation and photo-bleaching on the gamma-radiated laser’s performance. When the gamma radiation dose is within 10 krad(Si) with a radiation dose rate less than 0.4 rad(Si)/s, compared to the [...] Read more.

To improve the radiation resistance of Yb-doped fiber lasers, we investigate the influence of pre-radiation and photo-bleaching on the gamma-radiated laser’s performance. When the gamma radiation dose is within 10 krad(Si) with a radiation dose rate less than 0.4 rad(Si)/s, compared to the output power of a non-pre-radiated Yb-doped fiber laser, the pre-radiation technique could enhance the radiation resistance against gamma-ray. However, the mode instability threshold was decreased, which was caused by the cumulated radiation-induced attenuation of pre-radiation and radiation. Based on an electronic probe micro-analyzer, the Yb-doped active fiber was Yb-doped aluminophosphosilicate ternary fiber; therefore, the radiated defects were mainly hole-related defects. A laser diode centered at 532 nm was chosen as the photo-bleaching laser source, which could recover 45.2% of the radiated-induced attenuation and increase the mode instability threshold. This work demonstrates the influence of pre-radiation and photo-bleaching on the radiation resistance against the gamma-ray of Yb-doped fiber lasers, which are of significance in the design and fabrication of related fiber lasers. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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10 pages, 3775 KiB

Open AccessArticle

A 2 μm Dual-Wavelength Laser at Cryogenic Temperature with Balanced Simultaneous Emission

by Guangchao Ye, Wei Wang, Haicheng Liu, Wenqiang Xie, Shixing Xia, Qinggang Meng and Peng Lin

Appl. Sci. 2023, 13(9), 5750; https://doi.org/10.3390/app13095750 - 06 May 2023

Viewed by 898

Abstract

A Tm,Ho:YAP laser at cryogenic temperature is demonstrated for the first time with simultaneous emission at 2000 nm and 2119 nm. The feasibility of switching wavelength and achieving balanced output powers at two widely separated wavelengths has been confirmed by investigating the temperature [...] Read more.

A Tm,Ho:YAP laser at cryogenic temperature is demonstrated for the first time with simultaneous emission at 2000 nm and 2119 nm. The feasibility of switching wavelength and achieving balanced output powers at two widely separated wavelengths has been confirmed by investigating the temperature dependence of the laser spectra. The optimal temperature for balanced output evidently diminishes as the pump power density increases, thereby manifesting a rate of change quantified at 1.19 K/W. At the optimal temperature of 43.1 K, the optical-to-optical conversion efficiency of the Tm,Ho:YAP simultaneous dual-wavelength laser (SDWL) with a pump power of 11.8 W is 12.7%, corresponding to a slope efficiency of 15.8%. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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13 pages, 5028 KiB

Open AccessArticle

Computation and Verification of Spatial Rate Equations for an Electro-Optically Q-Switched Laser-Diode Side-Pumped Nd:YAG Laser

by Renpeng Yan, Haobo Xu and Xudong Li

Appl. Sci. 2023, 13(9), 5410; https://doi.org/10.3390/app13095410 - 26 Apr 2023

Viewed by 1579

Abstract

In a side-pumped laser module, we simulate the pumping power distribution across the cross-section of Nd:YAG rods at varying diameters. The coupled rate equations with the spatial overlap efficiency for a four-level actively Q-switched side-pumped laser are considered complete. After a Q-switched pulse [...] Read more.

In a side-pumped laser module, we simulate the pumping power distribution across the cross-section of Nd:YAG rods at varying diameters. The coupled rate equations with the spatial overlap efficiency for a four-level actively Q-switched side-pumped laser are considered complete. After a Q-switched pulse terminates, the expressions of laser output parameters are derived. We assess the single pulse energy, pulse width, and peak power using the analysis function. The 200 Hz Q-switched side-pumped Nd:YAG laser with a peak power of 103 kW and beam quality factors M² = 1.67 is developed to the validity of theoretical models. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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9 pages, 1938 KiB

Open AccessCommunication

Chaotic Optical Communication with Wavelength-Hopping Technology Based on Tunable Lasers

by Mi Li, Xinyu Zhang, Yizhuo Zhang, Zhiyuan Su, Xue Wang and Yijun Jiang

Appl. Sci. 2023, 13(9), 5276; https://doi.org/10.3390/app13095276 - 23 Apr 2023

Viewed by 1078

Abstract

With the development of communication technology, there is a more urgent demand for enhancing the security of data transmission. In order to improve the security of the traditional chaotic laser communication system, we propose a new scheme by the introduction of wavelength-hopping technology [...] Read more.

With the development of communication technology, there is a more urgent demand for enhancing the security of data transmission. In order to improve the security of the traditional chaotic laser communication system, we propose a new scheme by the introduction of wavelength-hopping technology based on tunable lasers. In our new scheme, due to the hopping of wavelengths and the pseudo-randomness of the wavelength-hopping sequence, it is difficult for the eavesdropper to intercept the information and predict to which wavelength the hopping station will hop. The numerical simulation results show that the average bit error rate of eavesdropping is about five orders of magnitude higher than that of working normally. This indicates that the introduction of wavelength-hopping technology can improve the difficulty of message decoding and improve the confidentiality of the system. This scheme can be used to realize a high level of privacy in the design of chaotic laser communication systems in the future. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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16 pages, 6603 KiB

Open AccessArticle

Adaptive Suppression Method of LiDAR Background Noise Based on Threshold Detection

by Yan Jiang, Jingguo Zhu, Chenghao Jiang, Tianpeng Xie, Ruqing Liu and Yu Wang

Appl. Sci. 2023, 13(6), 3772; https://doi.org/10.3390/app13063772 - 15 Mar 2023

Cited by 3 | Viewed by 2015

Abstract

Background radiation in the LiDAR detection field of view is complex and variable, and the background noise generated can easily cause false alarms in the receiver, which affects the effective detection of the system. Through the analysis of the influence of background radiation [...] Read more.

Background radiation in the LiDAR detection field of view is complex and variable, and the background noise generated can easily cause false alarms in the receiver, which affects the effective detection of the system. Through the analysis of the influence of background radiation noise of LiDAR on the detection performance, an adaptive suppression method of LiDAR background noise is proposed. This method realizes the rapid suppression of background noise in the instantaneous field of view through an adaptive threshold adjustment of current steering architecture with a back-end digital-to-analog converter (DAC) correction based on the principle of constant false alarm rate (CFAR) control. Aiming at the problem of accurate noise detection and quantification in a very short time, a dynamic comparator is used to replace the traditional continuous comparator. While detecting the number of noise pulses, the measurement of the pulse duration of noise is realized, which improves the accuracy of short-time noise detection. In order to verify the actual effect of the adaptive method, experiments were carried out based on the team’s self-developed LiDAR. The experimental results show that the measured noise ratio of the adaptive mode by using this method is the lowest. Even at 12 a.m., the noise ratio of the point cloud obtained by the adaptive mode is 0.012%, compared with 0.08% obtained by the traditional mode, which proves that this method has a good ability to suppress background noise. The proportion of noise reduction of the adaptive mode is more than 80% compared with the traditional mode. It achieves noise suppression through hardware at each detection, and each adjustment can be completed within a single period of pulse detection. Therefore, it has great advantages in real-time detection compared with the back-end software noise reduction processing method, and it is suitable for the application of LiDAR in the complex background environment. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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11 pages, 2759 KiB

Open AccessArticle

A 1 × 2 Two-Dimensional Slanted Grating Based on Double-Layer Cylindrical Structure

by Yuda Chen, Jin Wang, Yihan Wang, Xingxue Li, Ge Jin and Changhe Zhou

Appl. Sci. 2023, 13(4), 2270; https://doi.org/10.3390/app13042270 - 10 Feb 2023

Viewed by 1838

Abstract

Diffraction gratings play an increasingly important role in various planar optical systems, such as near-eye display systems for virtual reality (VR) and augmented reality (AR). The slanted gratings have more advantages than other elements. A 1 × 2 transmission two-dimensional (2D) slanted grating [...] Read more.

Diffraction gratings play an increasingly important role in various planar optical systems, such as near-eye display systems for virtual reality (VR) and augmented reality (AR). The slanted gratings have more advantages than other elements. A 1 × 2 transmission two-dimensional (2D) slanted grating based on a double-layer cylindrical structure was proposed in this paper. In the initial phase of this study, this kind of grating was proposed and designed. We used rigorous coupled-wave analysis (RCWA) and simulated annealing algorithm (SA) to optimize the grating parameters. The effects of the grating geometric parameters on the diffraction efficiency were investigated using rigorous coupled-wave analysis (RCWA). The simulated annealing algorithm (SA) optimization results show that the diffraction efficiency of the (0, −1) and (−1, 0) order exceed 35% under normal incidence in the range of 429–468 nm wavelength for TE and TM polarization. Meanwhile, the total diffraction efficiency can reach up to 78%. In the last section, we discuss the tolerances for the grating parameters to ensure high quality manufacturing processes. The total effective efficiency is greater than 75% when the MgF₂ thickness is from 300 nm to 350 nm and the SiO₂ thickness is from 525 nm to 550 nm. Moreover, the grating period has a 53 nm fabrication tolerance, and the slanted angle has a 8.8-degree fabrication tolerance. The relatively large tolerances ensure that it is easy to fabricate the two-dimensional slanted grating and to achieve the targeted objectives. The proposed 2D slanted grating can be applied to 2D exit pupil expansion, which is of great importance in AR/VR applications. Full article

(This article belongs to the Special Issue Advances in Optical and Optoelectronic Devices and Systems)

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