2023

• Record 397 of
  
  Title:The Multiple Scattering of Laser Beam Propagation in Advection Fog and Radiation Fog
  
  Author(s):Xu, Qiang(1); Cao, Yunhua(1); Zhang, Yuanyuan(1); Yan, Shaohui(2); Han, Yiping(1); Wu, Zhensen(1)
  Source: International Journal of Optics  Volume: 2023  Issue: null  Article Number: 9715482  DOI: 10.1155/2023/9715482  Published: 2023  
  Abstract:The laser beams were scattered and attenuated when they propagate in fogs for laser communication, laser remote sensing detection. For different density and droplets distribution of fogs, the laser scatter and attenuation are different, the correspond mechanism need thorough investigation. The characteristics of laser beam scattering in different types of fogs are studied based on the droplet size characteristics of advection fog and radiation fog, the scattering coefficients of droplets with different laser wavelengths(0.86 μm, 0.91 μm, 1.06 μm, 1.3015, and 10.6 μm) are calculated, the multi scattering of laser beam is studied by the Monte Carlo method, the propagation path and scattering direction of photons is analyzed, relations between asymmetry factor, albedo of fog droplets, and the visibility are presented, and the forward scattering intensity and the backward scattering intensity versus scattering angle are gotten and discussed. © 2023 Qiang Xu et al.
  Accession Number: 20230413448214
• Record 398 of
  
  Title:Optical Properties of Titanium-doped Gallium Oxide Thin Films by Thermal Atomic Layer Deposition
  
  Author(s):Li, Cunyu(1,2); Zhu, Xiangping(1,2); Zhao, Wei(1,2); Li, Jichao(1,2); Hu, Jingpeng(3)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 6  Article Number: 0631002  DOI: 10.3788/gzxb20235206.0631002  Published: June 2023  
  Abstract:Gallium oxide（Ga2O3）is a wide bandgap（4.8 eV）semiconductor oxide with the advantages of high transparency and excellent chemical and thermal stability. Therefore，Ga2O3 thin film has a wide range of applications in metal oxide field effect transistors，photodetectors and so on. However，the large bandgap of Ga2O3 is unfavorable to the conductivity，which limits the application of Ga2O3 film in optoelectronic devices. The optical and electrical properties of Ga2O3 can be significantly improved by elemental doping，thereby enhancing device performance. The lattice deformation of Ti-doped Ga2O3 （TGO）is small due to the close matching of the Shannon ion radii（0.060 5 nm，0.042 nm）of Ti4+ in octahedral and tetrahedral coordination with Ga3+（0.062 nm，0.047 nm）. The reported plasma-enhanced atomic layer deposition at 120 ℃ for the preparation of TGO films requires four precursors：triethyl gallium，oxygen plasma，titanium tetraisopropoxide（TTIP）and H2O. Using H2O as an oxidizer requires long purging times after water vapor exposure and brings in hydroxyl （-OH） impurities at deposition temperatures below 150 ℃. Compared with H2O，O3 has stronger oxidability and higher volatility and does not introduce impurities. In order to avoid the problems caused by using H2O as precursor. TiO2，Ga2O3 and TGO films are prepared by thermal atomic layer deposition using Trimethylgallium （TMG） and Tetrakis-dimethyl-amido Titanium（TDMAT）as precursor sources and O3 as reaction gas at 250 ℃. The Ti-doped Ga2O3 concentration is adjusted by designing the Ga2O3/TiO2 cycle ratio. TGO thin films form sandwich structure through different cycles（9，6 and 3）of Ga2O3 and 1 cycle of TiO2. The growth rates of Ga2O3 and TiO2 measured by spectroscopic ellipsometry are 0.037 nm/cycle and 0.08 nm/cycle，respectively. The growth rate of TGO film is lower than the theoretical calculated value due to the delayed growth of Ga2O3 nucleation caused by the decrease of surface reactive site density after TiO2 growth. The results of X-ray photoelectron spectroscopy show that the concentration of Ti in the film increases with the decrease of Ga2O3/TiO2 cycle ratio，the binding energy of O 1s，Ga 2p and Ti 2p shifts to the lower，which is attributed to the replacement of some sites of Ga by Ti atoms，indicating that Ti elements are successfully doped into Ga2O3 films. The core level spectra of TiO2 and Ga2O3 show the presence of Ti4+ and Ga3+ ions in the films. In the O 1s core level spectra of TGO films，Ga-O bonding decreases with increasing Ti-O bonding content，indicating the formation of Ga2O3-TiO2 composites in the TGO films. The absence of diffraction peaks in the grazing incidence X-ray diffraction spectra indicates that the deposited Ga2O3 and TGO films are amorphous. The surface root mean square roughness of 0.377 nm is observed by atomic force microscopy，indicating that the surface of the film is flat and smooth. This is attributed to the layer-by-layer growth of atomic layer deposition with the advantage of atomic-level thickness control. The TGO films exhibit high transparency in the visible region and strongly absorb ultraviolet light. With the increase of Ti doping concentration，the refractive index of TGO films increases from 1.75 to 1.99 due to chemical changes，the transmittance decreases due to the increase of extinction coefficient in the ultraviolet region，the absorption edge appears red-shifted and the optical bandgap decreases from 4.9 eV to 4.3 eV. The reduced band gap of TGO films can extend the sensitive region of optoelectronic devices to longer wavelengths. The optical band gap of thin films measured by spectrophotometric and X-ray photoelectron spectroscopy shows consistent results. The comprehensive analysis shows that Ti doping has a significant impact on the optical properties of Ga2O3. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20233014444780
• Record 399 of
  
  Title:Investigation on the Preparation of TiO2∶Al2O3 Nanocomposite Film Applied to the Conductive Layer of Microchannel Plate
  
  Author(s):Li, Jichao(1,2); Zhu, Xiangping(1,2); Li, Xiangxin(3); Hu, Jingpeng(3); Li, Cunyu(1,2); Zhao, Wei(1,2)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 6  Article Number: 0631003  DOI: 10.3788/gzxb20235206.0631003  Published: June 2023  
  Abstract:Microchannel Plate（MCP） is a high-gain electron multiplier that consists of a channel-type array of millions of single-channel electron multipliers tightly spaced parallel to each other. MCP is widely used in low-light night vision technology，time-of-flight mass spectrometry，and other fields due to its advantages of high electronic gain，high spatial resolution，high temporal resolution，and extremely low background noise. Traditional MCP is constructed of lead-silicate glass and is created by the processes of stretching，stacking，fusing，slicing，etching，and hydrogen reduction. After hydrogen reduction chemical treatment，a conductive layer and a Secondary Electron Emission（SEE）layer are formed. When MCP works，a DC high voltage is applied at both ends. When electrons or photons enter the channel，they collide with the SEE layer to excite secondary electrons，and then accelerate to bombard the tube wall under the action of an electric field to produce more electrons，resulting in the amplification of the input signal. However，because of the complicated manufacturing process of traditional MCP，its performance is difficult to improve. In recent years，Atomic Layer Deposition（ALD）has given a straightforward solution to the aforementioned issues. ALD is a thin film deposition technology capable of producing very thin conformal films. By exposing the substrate surface to alternate gases for successive surface reactions，the thickness and composition of the film are regulated at the atomic level. ALD can also deposit homogenous nano-films on substrates with high aspect ratio structures at the same time. Based on the benefits of ALD discussed above，the researchers recommend depositing a conductive layer and a SEE layer inside the channel to improve the performance of traditional MCP. Using ALD to functionalize the MCP can remove the functional layer from the glass substrate，allowing for variable modification of the conductive layer and emission layer based on individual demands，therefore simplifying the production process，and improving MCP performance. The MCP conductive layer is responsible for conducting current and supplementing electrons in SEE layer. If the resistivity of the conductive layer is too large，the electron charge of the SEE layer can not be replenished in time，causing the MCP to saturate ahead of time and lower its electrical gain. If the resistivity is too small，the current going through the MCP will be too strong，resulting in a thermal effect and MCP damage. At the moment，the conductive layer films produced by ALD are mainly ZnO∶Al2O3（AZO），W∶Al2O3，and Mo∶Al2O3 composite materials. However，there are several issues with these conductive layer film materials. Because MCP requires a high-voltage environment，but the performance of AZO thin film is unstable and easily broken down under high voltage，and the precursors of W and Mo are costly and very poisonous，there are issues such as safety and economy in industrial mass production. As a result，it is critical to design a novel conductive layer composite film to address both safety and economic concerns. Al2O3 is a typical dielectric material with a high dielectric constant and resistance. TiO2 has excellent electrical characteristics as well as chemical stability. Simultaneously，the precursors of Al2O3，Al （CH3）3（TMA），and the precursor of TiO2，Ti （N（CH3）2）4（TDMAT），have the benefits of cheap cost，non-toxic，and innocuous reaction by-products. In this paper，we propose TiO2∶Al2O3 nanocomposite films as the conductive layer of MCP. Based on the bulk resistance of the MCP，we first calculated the sheet resistance requirements of the conductive layer and found that for a channel with an aperture of 10 μm，a center distance of 12 μm，an aspect ratio of 48∶1，a diameter of 25 mm and a diameter of 20.5 mm in the active area for MCP，when the bulk resistance value is 100~300 MΩ，the sheet resistance value range of the conductive layer should be 1.73×1013~5.20×1013 Ω/. On borosilicate glass substrates， we used ALD to deposit TiO2∶Al2O3 nanocomposite films with varying TiO2 cycle percentages. The square resistance of TiO2∶Al2O3 nanocomposite films is found to be within the required range of the square resistance of the conductive layer when the TiO2 cycle percentage is between 30.27%~ 37.06%. A 20 nm Al2O3 transition layer and a 100 nm TiO2∶Al2O3 nanocomposite film are designed and prepared on a p-type single-sided polished monocrystalline silicon（100）substrate. The thickness of the film is measured by SEM to be 122 nm，and the surface is flat and smooth. Finally，the conductive layer of TiO2∶Al2O3 nanocomposite film in the MCP is prepared. The measured bulk resistance is 212.81 MΩ@ 1 000 V，and the gain is 18 357@1 000 V. To summarize，the TiO2∶Al2O3 nanocomposite film we developed can well meet the requirements of the MCP conductive layer and has the advantages of low cost，high voltage resistance，low corrosivity，and high safety，providing a new material choice for the development of ALD-MCP. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20233014444820
• Record 400 of
  
  Title:Sensitive label-free hemoglobin detection based on polydopamine functionalized graphene oxide coated micro-tapered long-period fiber grating
  
  Author(s):Li, Yansong(1); Du, Mengyu(1); He, Shuxuan(1); Wang, Ruiduo(2); Zhang, Zaikun(2); Wang, Qiang(1)
  Source: Optik  Volume: 275  Issue: null  Article Number: 170626  DOI: 10.1016/j.ijleo.2023.170626  Published: March 2023  
  Abstract:The GO and PDA-GO functionalized TLPG based sensitive and label-free optical biosensor for human hemoglobin detection was demonstrated. The PDA-GO and GO were separately deposited onto fiber surface, the deposited materials provide a large number of binding sites to adsorb the hemoglobin and can further change the RI of fiber surface, and can provide more binding sites owing to the large specific surface area, and it exhibits higher sensing sensitivity of 3.14 mg/mL and the LOD can reach 0.057 mg/mL. In addition, the sensing was carried out in the presence of inference compounds and also proved its ideal reusability. The usage of PDA-GO as a bio-interface layer enables strong interference of optical waves as well as excellent biocompatibility, which is considered to be valuable for biosensing applications. © 2023
  Accession Number: 20231113704388
• Record 401 of
  
  Title:Theoretical Simulation and Preparation of Anti-reflection Characteristics of Zinc Sulfide Surface Microstructure
  
  Author(s):Luo, Xing(1,2); Li, Ming(1,2); Mao, Jianyong(3)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 7  Article Number: 0752308  DOI: 10.3788/gzxb20235207.0752308  Published: July 2023  
  Abstract:Zinc sulfide is a widely used infrared window material. Due to its high refractive index and strong surface Fresnel reflection，improving its anti reflection performance in the infrared band is of great significance. The traditional method to improve the antireflective performance is to prepare a film on the surface of zinc sulfide，but the antireflective film has the disadvantage of detachment and it is a limited antireflection effect on infrared signals with a wide spectrum and a large angle incidence. Preparing subwavelength structures on the surface of zinc sulfide can effectively improve its antireflective performance. This can be achieved by adjusting the microstructure parameters. Femtosecond laser processing has unique advantages of programmability and non-contact，making it a promising one-step manufacturing method for subwavelength microstructures. In this paper，the finite difference time-domain method is used to simulate the antireflection characteristics of the zinc sulfide surface structure，which is prepared by femtosecond laser processing，and then the infrared transmittance of the structure array surface is measured. This article is based on zinc sulfide material，simulating and preparing one-dimensional strip structure and two-dimensional grid structure and further testing the infrared transmittance of both structures. Firstly，FDTD software was used to simulate and calculate the infrared transmittance characteristics of the zinc sulfide surface structure.Determine the unit structural parameters of the structural array by simulating the height of the strip structure. On this basis，two types of structural arrays with different spacing were designed，and the simulation results showed that as the spacing between structures decreased，the transmittance increased. The trend exhibited by one-dimensional strip structures and two-dimensional grid structures is consistent. Secondly，two types of structural arrays were prepared using femtosecond laser processing. The test results indicate that as the spacing between the one-dimensional strip structures decreases，the transmittance tends to increase，which is similar to the trend shown by simulation. The two-dimensional grid structure with small spacing has higher roughness，so the structure array with 8 spacing has better transmittance. In actual processing，it is necessary to comprehensively consider the influence of surface roughness and ablation degree on the transmittance，and reduce the Fresnel scattering of light waves by edge cracks. Finally，the transmittance of the samples was tested in the range of 7~10 μm in the mid to far infrared bands. The structure array with a spacing of 5 μm increases the infrared transmittance by approximately 6% at wavelengths 9.5~10 μm. The grid structure with a spacing of 8 μm can increase the average transmittance by 4% in the 8.5~10 μm bands and nearly 7% at the 10 μm wavelengths. In addition，the transmittance spectrum measured in the experiment has good transmittance in the long wavelength range，which is related to the scattering effect of nanoscale structures generated by laser processing at different wavelengths，the surface scattering effect of non-uniform micro nano composite structures is more pronounced at shorter wavelengths. Compared with the simulation result，it was found that the overall transmittance of zinc sulfide decreased. The overall decrease in the transmittance of zinc sulfide samples is related to two factors：the first reason is the light absorption effect caused by structural defects in femtosecond laser processing，part of the light is absorbed by zinc sulfide，and the second reason is the diffraction and light scattering effects caused by non-uniform surface particulate matter generated by laser processing，which deflects the incident light along the beam transmission path. The experimental results indicate that the prepared structure has good anti-reflection performance，indicating that the method used in this paper has a positive effect on improving the transmittance of zinc sulfide. This provides a reference for studying the transmittance of zinc sulfide in the mid-infrared band. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20233714721524
• Record 402 of
  
  Title:D-shaped terahertz microstructured fiber biosensor based on plasmon resonance on graphene surface
  
  Author(s):Zhang, Yani(1,2); Xue, Jia(1,2); Zhang, Yunxia(2); Miao, Ting(2); Yao, Yiming(2); Wang, Qiuyang(2); Gong, Jiaqin(2)
  Source: 2023 21st International Conference on Optical Communications and Networks, ICOCN 2023  Volume: null  Issue: null  Article Number: null  DOI: 10.1109/ICOCN59242.2023.10236355  Published: 2023  
  Abstract:This paper designs a D-shaped microstructured fiber optic biosensing model based on surface plasmon resonance of graphene, which is dedicated to the terahertz frequency band. Improving optical fiber sensing performance by adjusting graphene thickness and graphene chemical potential to increase peak spectral loss. The optimization results show that the resonance peak decreases with increasing excitation layer thickness and graphene chemical potential. Moreover, the higher the graphene chemical potential, the more the resonance spectrum is shifted towards the higher frequency band. The maximum frequency sensitivity is 1300 GHz/RIU over a refractive index sensing range of 1.1-1.5, corresponding to a quality factor of 1.0× 10 4 RIU. In conclusion, the proposed D-type microstructured optical fiber has a novel and ingenious structure with high detection accuracy. With graphene as the excitation medium, the microstructured optical fiber operating band is successfully extended to the terahertz band, opening up a broader application prospect for the microstructured optical fiber structure in the THz sensing field. © 2023 IEEE.
  Accession Number: 20234014844507
• Record 403 of
  
  Title:Analysis of Trace Metal Elements in Water Based on Discharge-Assisted Laser-Induced Breakdown Spectroscopy
  
  Author(s):Xu, Boping(1,2); Liu, Yinghua(1,2); Liu, Zaihao(1,2); Yin, Peiqi(1,2); Tang, Jie(1,2)
  Source: Diangong Jishu Xuebao/Transactions of China Electrotechnical Society  Volume: 38  Issue: 17  Article Number: null  DOI: 10.19595/j.cnki.1000-6753.tces.L10087  Published: September 2023  
  Abstract:Heavy metal ion-induced water pollution has become a severe environment in the world. Laser-induced breakdown spectroscopy (LIBS) is a novel analytical technique based on the atomic emission spectroscopy, which can be used for the target in any state. Thus, LIBS is widely applied in various applications, including environmental pollution monitoring, food safety, and chemical engineering production. However, for liquid sample detection, the rapid quenching of the plasma, the contamination of the optical system by the unstable liquid level, and the limited laser energy absorption of the plasma have limited the further development of LIBS technology. Here, a discharge-assisted LIBS technique (D-LIBS) for the detection of trace elements in solutions is proposed and compared with the conventional LIBS (C-LIBS). Rapid sampling of mixed BaCl2 and NaCl2 solutions is performed using medium-speed filter paper. A Nd:YAG laser is implemented to generate plasmas containing the target elements on the filter paper. A discharge assistance consists mainly of a high voltage DC power supply, a capacitor, and a pair of rod electrodes. The capacitor is first charged by the high voltage DC power supply. The electrodes are respectively connected to the positive and negative terminals of the capacitor, and placed horizontally on the surface of the filter paper. Once the sample surface is ablated by the focused laser beam, the pre-existing plasma between the electrodes acts as the seed charged particles in the discharge gap, which rapidly ignites a strong discharge there. Compared to the time-integrated spectra in C-LIBS and D-LIBS, the LIBS signal has been greatly increased by using the discharge assistance. Emission lines of BaⅡ455.40 nm and NaⅠ588.99 nm are respectively enhanced to 30-fold and 6-fold. The spectral intensities in C-LIBS and D-LIBS are positively correlated with laser energy. However, the spectral enhancement factors show higher values at small laser energy conditions, and the BaⅡ spectral enhancement factor decreases from 30 (20 mJ) to 2 (50 mJ) with increasing laser energy. Compared with the spectral signal-to-noise ratio (SNR) in C-LIBS, D-LIBS results in a SNR enhancement of more than 1 order of magnitude. When the laser energy is 20 mJ, the SNR enhancement factor of BaⅡ spectral line and Na I spectral line is 56 and 16, respectively. In addition, the quantitative analysis performance of C-LIBS and D-LIBS for trace metal elements in solution under different laser energy conditions are comparatively studied. The limit of detection (LoD) of Ba is decreased along with the laser energy in C-LIBS, reaching 0.823 mg/L at 50 mJ. Moreover, under the optimal condition the LoD is reduced from 12.5 mg/L in C-LIBS to 0.26 mg/L in D-LIBS, and the detection sensitivity of LIBS technique is increased by 47-fold due to the discharge assistance. The following conclusions can be drawn from the experimental results: (1) The spectral intensity, SNR can be enhanced by over 1 order of magnitude. The increases in the intensity and SNR of the plasma spectra are due to the additional electrical energy injection resulting in the reheating and excitation of the plasma. (2) The spectral intensity and SNR are positively correlated with laser energy. The enhancement factor reaches the maximum in the smallest laser energy condition. This is due to the fact that the lower the laser energy, the smaller the mass of sample ablated, and therefore the more significant the enhancement effect is when the plasma is excited by the additional discharge. (3) The quantitative analysis of LIBS can be efficiently enhanced over 1 order of magnitude by the discharge assistance. And the LoD is reduced to 0.26 mg/L which is 1/48 of the original level. © 2023 Chinese Machine Press. All rights reserved.
  Accession Number: 20234214885766
• Record 404 of
  
  Title:Engraving Depth-Controlled Nanohole Arrays on Fused Silica by Direct Short-Pulse Laser Ablation
  
  Author(s):Liu, Xin(1,2); Clady, Raphaël(1); Grojo, David(1); Utéza, Olivier(1); Sanner, Nicolas(1)
  Source: Advanced Materials Interfaces  Volume: 10  Issue: 7  Article Number: 2202189  DOI: 10.1002/admi.202202189  Published: March 6, 2023  
  Abstract:Periodic nanohole arrangements constitute an important building block of advanced photonic devices. Aside from standard nanofabrication tools, a direct laser-based approach is introduced here, that enables single-step and point-by-point machining of arrays of holes with subwavelength diameters and depths reaching several micrometers at the surface of fused silica. The method relies on a simple optical arrangement including an axicon combined with an amplitude mask to shape the laser intensity in appropriately truncated micro-Bessel beams of adjustable length. The suitability and limitations of the technique are investigated to fabricate arrays of cylindrical nanoholes with tunable depths. In particular, the challenge of avoiding crosstalk effects during the laser-writing process of high-density arrays is explored. The achievability of square arrays of nanoholes at the surface of fused silica, with diameters down to 200 nm and variable depths from 3 to 20 µm at a spatial density defined by a pitch of 1.5 µm is demonstrated. The performance level shows the potential of the direct-laser-processing method towards the realization of integrated devices, offering a highly flexible and cost-effective alternative technique to current nanofabrication methods. © 2023 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.
  Accession Number: 20230513463019
• Record 405 of
  
  Title:High Photon Efficiency Image Reconstruction Algorithm Based on Depth Range Selection for Single Photon Counting LiDAR
  
  Author(s):Meng, Fanxing(1,2); Zhang, Tongyi(1,2); Kang, Yan(1); Xue, Ruikai(1,2); Wang, Xiaofang(1,2); Li, Weiwei(1,2); Li, Lifei(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 52  Issue: 9  Article Number: 0910001  DOI: 10.3788/gzxb20235209.0910001  Published: September 2023  
  Abstract:Photon counting imaging technology is a new type of active imaging technology，which obtains depth information of the target by accumulating histograms of echo photons. It can be combined with Time-correlated Single-photon Counting（TCSPC）to achieve high temporal resolution. Compared with passive imaging systems，it has stronger robustness and is widely used in fields such as biomedicine，target recognition and remote sensing imaging. But it takes a long time to accumulate thousands of echo photons. In some environments with low Signal-to-background Ratio（SBR）and very few echo photons，such as military reconnaissance and other fields，long-term data collection can not be satisfied，and the ability to reconstruct 3D scenes is affected by noise photons and vacant pixels. This paper proposes a high photon efficiency image reconstruction algorithm based on depth range selection. The algorithm achieves strong resistance to noise and fully improves photon utilization efficiency through two steps：selection of target depth range，adaptive supplementation and TV regularization. Specifically，the selection of the target depth range allows us to gain depth range at the initial stage of the reconstruction process，paving the way for subsequent processing. This process is divided into five steps：merging all data into histogram，peak searching for the histogram，potential signal range determination，signal range review and select signal range. These five processes can ensure that the depth range we obtain is more accurate than setting threshold gating to the histogram. The photon screening process can remove all the noise outside the depth range，thereby reducing the error we introduce when we fill in the vacant pixels. Compared with relying on fixed neighborhood data to supplement vacancies，supplementation using adaptive neighborhood data has a higher photon utilization efficiency and will be more suitable for environments with very few echo photons. Finally，TV regularization is used to smooth the residual noise in the depth range. The simulation and experimental process have verified that even in the case of low SBR and very few echo photons，our algorithm can still effectively reconstruct the 3D image of the scene. We reconstructed the simulation data of different degrees of echo photons when SBR=0.04 and compared it with the high photon efficiency algorithm and the Unmixing method. We also input the data preprocessed by the proposed method into the Unmixing method for processing （Preprocess-unmixing，PP-Unmixing） to verify the contribution of accurately selecting the target depth range. The preprocessing here only includes the selection of target depth range. The results show that our method can distinguish scene edges in any case， and the reconstruction effect and RMSE are better than the other three methods. Our proposed method is also a fast reconstruction method. In addition，a comparison between the PP-Unmixing method and the Unmixing method proves the necessity of accurately selecting the target depth range. In addition to the simulated data，two experimental scenarios further verify the feasibility of the proposed algorithm. In experimental scenario 1，SHIN D's method can not accurately estimate the depth range，resulting in a large deviation in the reconstructed depth map. And as the number of echo photons decreases， the image becomes increasingly blurred and the scene cannot be resolved，even though it has a fast reconstruction speed. The Unmixing method is better than SHIN D's method in terms of reconstruction effect，but it still can not completely reconstruct the scene in the case of fewer echo photons，the filtering for noise is not thorough enough，and its running speed is still the slowest. The method proposed in this paper can clearly distinguish the scene in any case. Even in the extreme environment with SPPP=0.47，the time-consuming and RMSE of results are only 0.032 m and 37.2 s. In experimental scenario 2，our method can retain more detailed information than the other two methods，especially in the extreme case when the SPPP=0.7，and the other two methods can hardly detect the house information. Further，in terms of RMSE and time consumption，SHIN D's method is the fastest，but its RMSE is the largest，and the RMSE of the Unmixing method is comparable to our method， but the reconstruction speed is still the slowest. Therefore， our method has more advantages in comprehensive ability and is more suitable for an environment with few echo photons and low SBR. In summary，our method has a significant reconstruction effect on both simulation data and experimental data，which proves that this method is more suitable for the situation of extremely low SBR and a very small number of echo photons. In terms of computing speed，it is also a fast reconstruction method. In addition，the proposed method has better applicability to the situation where there are multiple depth targets in the scene，and further research and verification will be carried out in the future. © 2023 Chinese Optical Society. All rights reserved.
  Accession Number: 20234014834427
• Record 406 of
  
  Title:Generation of Q-switched fiber laser based on ferroferric oxide in 1.55 µm region
  
  Author(s):Nie, Liang(1); Duan, Zhixia(2); Liu, Ruisheng(3,4); Zhang, Danni(1); Li, Xiaohui(3); Wang, Wei(1); Gao, Cunxiao(4); Xue, Mingyuan(4)
  Source: Infrared Physics and Technology  Volume: 134  Issue: null  Article Number: 104876  DOI: 10.1016/j.infrared.2023.104876  Published: November 2023  
  Abstract:To improve the performance of fiber lasers, a Q-switched fiber laser based on iron oxide nanomaterials was developed. The pump power was gradually increased, and the corresponding data of the Q-switched pulse frequency and spectral width were recorded. When a pump power of 170 mW was reached, the Q-switched pulse frequency of 48.45 kHz, pulse width of 2.3 μs, center wavelength of 1530.4 nm, and spectral width of 3.8 nm were observed and recorded. The Q-switched pulse frequency was increased from 30.53 kHz to 58.74 kHz, along with an increase in the pump power from 45 mW to 250 mW. The spectral width was decreased from 7.31 nm to 2.04 nm, and this change was duly recorded. The Q-switched fiber laser demonstrated has good output characteristics and can be applied to scientific research, medical treatment, industrial processing and other fields. © 2023 Elsevier B.V.
  Accession Number: 20233714715325
• Record 407 of
  
  Title:Compact lensless optoelectronic convolutional neural network for image classification
  
  Author(s):Zhang, Zaikun(1,2,3); Da, Zhengshang(3); Kong, Depeng(1); Wang, Ruiduo(1,2); Mu, Qiyuan(1,2); Wang, Shijie(1); Geng, Yi(4); He, Zhengquan(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12935  Issue: null  Article Number: 129350F  DOI: 10.1117/12.3000602  Published: 2023  
  Abstract:Recently, free-space optical neural networks (ONNs) have gained extensive interest as emerging machine learning platforms for implementing artificial intelligence tasks, such as image classification. Despite various optical implementations of electronic neural networks (ENNs), the bulky volume of optical components remains challenging to deploy edge devices, such as Internet of Things peripherals, wearable devices, and camera. To address this problem, we propose a compact lensless optoelectronic convolutional neural network (LOE-CNN) architecture with a lensless optical analog processor utilizing a single optimized diffractive phase mask (DPM) to perform convolution operations without Fourier lens. Comparing the processor with a commercially available NVIDIA A100 Tensor Core GPU in terms of speed and power, indicates the optical computing platform enables to replace the electronic processor in latency reduction and energy savings. Furthermore, we compare the LOE-CNN with two all-electronic neural networks (i.e., fully connected neural network [FC-NN] and convolutional neural network [CNN]) over the Modified National Institute of Standards and Technology (MNIST) dataset and Fashion-MNIST dataset, respectively, and demonstrate that the LOE-CNN can be functionally comparable to existing electronic counterparts in classification performance. My study not only opens up new application prospects for free-space ONNs based on compact lensless single-chip convolution processor, but also facilitates the development of ONNs-based smart devices. © 2023 SPIE.
  Accession Number: 20235015220890
• Record 408 of
  
  Title:High-precision gaseous flame temperature field measurement based on quadriwave-lateral shearing interferometry
  
  Author(s):Yuan, Xun(1,2); Xue, Yuge(1,2); Min, Junwei(1); Yu, Xianghua(1); Li, Manman(1); Li, Runze(1); Yao, Baoli(1,2)
  Source: Optics and Lasers in Engineering  Volume: 162  Issue: null  Article Number: 107430  DOI: 10.1016/j.optlaseng.2022.107430  Published: March 2023  
  Abstract:Quadriwave-lateral shearing interferometry (QLSI) has a broad utilization in quantitative phase imaging (QPI) for refraction-type objects due to its compact structure and stable performance against external disturbance. Here we propose to use the QLSI technique to image and measure the gaseous flame temperature field distribution in high precision. The quantitative phase image of an axisymmetric candle flame is firstly reconstructed from the wire-mesh-like QLSI interferogram, and then the three-dimensional temperature field distribution is calculated with the axisymmetric projection transform algorithm. Compared to the conventional digital holographic interferometry (DHI) based on Mach-Zehnder architecture, the proposed method possesses a high-precision measurement and better stability in disturbed environment, benefiting from the compact common-path structure of QLSI. The temperature measurement errors of the proposed QLSI method are ±5.0 K and ±5.3 K in the presence of airflow disturbance and mechanical vibration, respectively, while those of the DHI method are ±7.6 K and ±12.9 K, respectively. © 2022 Elsevier Ltd
  Accession Number: 20230213361633