In the paper, the Nd:YAG laser with an intracavity axicon that directly generated high-order vortex Bessel-Gaussian(BG) modes under both quasi-continuous and Q-switched operation was demonstrated. In quasi-continuous operation, a coherent superposition of opposite-handedness vortex modes yielded a petal-shaped transverse intensity. By adjusting the distance between the axicon and output coupler, the relative power ratio between the J0 and high-order BG components could be varied, also allowing order tuning. The orbital angular momentum(OAM) reached beyond |l|=34. The maximum average power was 1.1 W with a 17.4 % optical-to-optical efficiency. Under Q-switched operation. The pulse energy reached 56 mJ with a 45 ns duration. The OAM was measured to exceed |l|=6 with self-interference scheme. The BG output exhibited non-diffracting propagation and self-reconstruction after partial obstruction. These results established a compact and robust route to tunable, high-order BG vortex beams generated inside the cavity, which are promising for OAM-multiplexed free-space links, imaging and ranging in scattering media, and precision spatial metrology.
{"title":"Intracavity-generated high-order Bessel-Gaussian vortex beams with axicon lens under quasi-continuous and Q-switched operation","authors":"Yilan Chen, Wenwen Hu, Donghui Zhang, Xiulin Qiu, Jian Cui, Yuxin Wei, Xiaobo Zhuang","doi":"10.1016/j.optlaseng.2026.109616","DOIUrl":"10.1016/j.optlaseng.2026.109616","url":null,"abstract":"<div><div>In the paper, the Nd:YAG laser with an intracavity axicon that directly generated high-order vortex Bessel-Gaussian(BG) modes under both quasi-continuous and Q-switched operation was demonstrated. In quasi-continuous operation, a coherent superposition of opposite-handedness vortex modes yielded a petal-shaped transverse intensity. By adjusting the distance between the axicon and output coupler, the relative power ratio between the J<sub>0</sub> and high-order BG components could be varied, also allowing order tuning. The orbital angular momentum(OAM) reached beyond |<em>l</em>|=34. The maximum average power was 1.1 W with a 17.4 % optical-to-optical efficiency. Under Q-switched operation. The pulse energy reached 56 mJ with a 45 ns duration. The OAM was measured to exceed |<em>l</em>|=6 with self-interference scheme. The BG output exhibited non-diffracting propagation and self-reconstruction after partial obstruction. These results established a compact and robust route to tunable, high-order BG vortex beams generated inside the cavity, which are promising for OAM-multiplexed free-space links, imaging and ranging in scattering media, and precision spatial metrology.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109616"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-10DOI: 10.1016/j.optlaseng.2026.109613
ZhiYuan Wang , Hao Weng , RongXin Tang , Can Su , HongJie Wang , Jie Tan , GuoHong Dai , Wei Tu , LiXin Gan , WeiChao Yan
Foggy environments degrade image quality by reducing contrast and sharpness, hindering critical information extraction. To overcome these challenges, we propose an atmospheric scattering model-informed feature extraction network (ASMFEN) that synergistically integrates frequency and spatial domain analysis. The ASMFEN employs Fourier transforms to decompose foggy images into frequency components, enabling targeted noise suppression across frequency bands and enhanced clarity. Spatial domain features are concurrently processed to preserve structural integrity. A multi-loss framework, in which the "self-supervised" component is realized via a physics-based reconstruction loss, ensures reconstruction fidelity and balances artifact suppression with detail preservation. On the synthetic SOTS dataset, ASMFEN achieves state-of-the-art quantitative performance, with a PSNR of 31.45±1.25 dB, SSIM of 0.9673±0.012, and NIQE of 2.69±0.06, outperforming Dark Channel Prior (DCP), DRHNet, and other deep learning models. Qualitative assessments on the URHI real-image dataset reveal enhanced color fidelity, preservation of fine details, and minimal artifacts. Notably, ASMFEN achieves an inference time of 0.029 s and total parameters of 2.4 × 108, ensuring practical efficiency for real-time applications. By unifying frequency and spatial domain insights, ASMFEN advances defogging performance across metrics, visual realism, and computational efficiency, offering a robust solution for complex real-world scenarios.
{"title":"Image dehazing with self-supervised physical consistency via atmospheric scattering model-informed feature extraction network","authors":"ZhiYuan Wang , Hao Weng , RongXin Tang , Can Su , HongJie Wang , Jie Tan , GuoHong Dai , Wei Tu , LiXin Gan , WeiChao Yan","doi":"10.1016/j.optlaseng.2026.109613","DOIUrl":"10.1016/j.optlaseng.2026.109613","url":null,"abstract":"<div><div>Foggy environments degrade image quality by reducing contrast and sharpness, hindering critical information extraction. To overcome these challenges, we propose an atmospheric scattering model-informed feature extraction network (ASMFEN) that synergistically integrates frequency and spatial domain analysis. The ASMFEN employs Fourier transforms to decompose foggy images into frequency components, enabling targeted noise suppression across frequency bands and enhanced clarity. Spatial domain features are concurrently processed to preserve structural integrity. A multi-loss framework, in which the \"self-supervised\" component is realized via a physics-based reconstruction loss, ensures reconstruction fidelity and balances artifact suppression with detail preservation. On the synthetic SOTS dataset, ASMFEN achieves state-of-the-art quantitative performance, with a PSNR of 31.45±1.25 dB, SSIM of 0.9673±0.012, and NIQE of 2.69±0.06, outperforming Dark Channel Prior (DCP), DRH<img>Net, and other deep learning models. Qualitative assessments on the URHI real-image dataset reveal enhanced color fidelity, preservation of fine details, and minimal artifacts. Notably, ASMFEN achieves an inference time of 0.029 s and total parameters of 2.4 × 10<sup>8</sup>, ensuring practical efficiency for real-time applications. By unifying frequency and spatial domain insights, ASMFEN advances defogging performance across metrics, visual realism, and computational efficiency, offering a robust solution for complex real-world scenarios.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109613"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-06DOI: 10.1016/j.optlaseng.2025.109595
Meiling Gao , Guangyu Zhao , Xuedong He , Xiaoyu Jin , Jin Duan , Huilin Jiang
To address the challenges of severe noise interference, insufficient global degradation capture, and artifact-prone enhancement in low-illumination division-of-focal-plane (DoFP) color polarimetric images, we propose StokesMamba, a dual-branch low-light color polarimetric image enhancement method based on Mamba and Stokes vector representations. First, a linear irradiance compensation is applied to the degraded Stokes vector, with a scaling factor γ used to enhance signal amplitude, mitigating feature masking caused by low signal-to-noise ratio (SNR). Subsequently, a dual-branch enhancement structure is designed based on the distinct physical properties of the Stokes components: the S0 branch combines adaptive intensity compression in the horizontal/vertical-intensity (HVI) color space with the denoising block (DB) module and intensity Mamba (IMamba) for artifact-free brightness enhancement, while the S1,2 branch leverage the gradient characteristics of differential images, incorporating the DB module and polarization Mamba (PMamba) to enhance edge and detail features. Experimental results demonstrate that our method outperforms existing approaches on the LLCP and PLIE datasets, achieving superior performance in terms of PSNR, SSIM, and visual quality.
{"title":"Stokes vector-based mamba for low-light color polarimetric image enhancement","authors":"Meiling Gao , Guangyu Zhao , Xuedong He , Xiaoyu Jin , Jin Duan , Huilin Jiang","doi":"10.1016/j.optlaseng.2025.109595","DOIUrl":"10.1016/j.optlaseng.2025.109595","url":null,"abstract":"<div><div>To address the challenges of severe noise interference, insufficient global degradation capture, and artifact-prone enhancement in low-illumination division-of-focal-plane (DoFP) color polarimetric images, we propose StokesMamba, a dual-branch low-light color polarimetric image enhancement method based on Mamba and Stokes vector representations. First, a linear irradiance compensation is applied to the degraded Stokes vector, with a scaling factor γ used to enhance signal amplitude, mitigating feature masking caused by low signal-to-noise ratio (SNR). Subsequently, a dual-branch enhancement structure is designed based on the distinct physical properties of the Stokes components: the S0 branch combines adaptive intensity compression in the horizontal/vertical-intensity (HVI) color space with the denoising block (DB) module and intensity Mamba (IMamba) for artifact-free brightness enhancement, while the S1,2 branch leverage the gradient characteristics of differential images, incorporating the DB module and polarization Mamba (PMamba) to enhance edge and detail features. Experimental results demonstrate that our method outperforms existing approaches on the LLCP and PLIE datasets, achieving superior performance in terms of PSNR, SSIM, and visual quality.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109595"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-07DOI: 10.1016/j.optlaseng.2025.109593
João Preizal , Ricardo Oliveira
This work presents a novel interferometric structure based on two single-mode fibers twisted and fused in a helical structure through a commercial CO2 laser processing station. The resulting device induced macrobending effects that promote light coupling from the core to the cladding and vice versa, creating an interferometric pattern in the transmission spectrum due to the phase difference between the light travelling in the core and cladding regions. The influence of the twist period on the spectral response showed an increased attenuation and higher fringe contrast for shorter twist periods, i.e., low bending radius. The sensing capabilities of the structure were evaluated for torsion, strain, and temperature, yielding sensitivities of −0.49 nm/(rad/m), –8.8 pm/με, and –81 pm/ °C, respectively. Temperature cross-sensitivity was also evaluated, showing values of 0.17 (rad/m)/ °C for torsion and 9 με/ °C for strain. These results highlight the potential of the structure for torsion sensitivity with high sensitivity and low cross-sensitivity. Therefore, this work demonstrates as well that these parameters can be measured using conventional single-mode fiber structures instead of complex and more expensive optical fibers, thereby reducing both cost and system complexity through a simpler and automated fabrication process compared with other fiber-optic sensors.
{"title":"Multiparameter sensing by permanent macrobending deformation","authors":"João Preizal , Ricardo Oliveira","doi":"10.1016/j.optlaseng.2025.109593","DOIUrl":"10.1016/j.optlaseng.2025.109593","url":null,"abstract":"<div><div>This work presents a novel interferometric structure based on two single-mode fibers twisted and fused in a helical structure through a commercial CO<sub>2</sub> laser processing station. The resulting device induced macrobending effects that promote light coupling from the core to the cladding and vice versa, creating an interferometric pattern in the transmission spectrum due to the phase difference between the light travelling in the core and cladding regions. The influence of the twist period on the spectral response showed an increased attenuation and higher fringe contrast for shorter twist periods, i.e., low bending radius. The sensing capabilities of the structure were evaluated for torsion, strain, and temperature, yielding sensitivities of −0.49 nm/(rad/m), –8.8 pm/με, and –81 pm/ °C, respectively. Temperature cross-sensitivity was also evaluated, showing values of 0.17 (rad/m)/ °C for torsion and 9 με/ °C for strain. These results highlight the potential of the structure for torsion sensitivity with high sensitivity and low cross-sensitivity. Therefore, this work demonstrates as well that these parameters can be measured using conventional single-mode fiber structures instead of complex and more expensive optical fibers, thereby reducing both cost and system complexity through a simpler and automated fabrication process compared with other fiber-optic sensors.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109593"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-07DOI: 10.1016/j.optlaseng.2025.109584
Valentina Lobo-Ruiz, Alejandro Velez-Zea, John Fredy Barrera-Ramírez
This work presents a non-iterative method for generating high-quality phase-only holograms based on the optimization of a complex field. To achieve this, an initial complex field is defined such that its product with a target amplitude yields an approximate phase-only hologram of the target after backward propagation. The complex field is then optimized using stochastic gradient descent to minimize a loss function, calculated between each hologram reconstruction and the corresponding target amplitude over a large image database. This enables the use of the optimized complex field (OCF) as a universal pre-computed function for the fast, non-iterative generation of holograms for any target. Numerical evaluations demonstrate that holograms generated with the OCF achieve superior reconstruction quality, as measured by correlation coefficient, mean squared error, and structural similarity, compared to those generated using random phase and optimized Fresnel random phase (OFRAP) methods across various epochs and propagation distances. The effectiveness of the proposed OCF method is further validated through experimental demonstrations in a holographic projection setup using a phase-only spatial light modulator.
{"title":"Optimized complex fields for non-iterative generation of phase holograms","authors":"Valentina Lobo-Ruiz, Alejandro Velez-Zea, John Fredy Barrera-Ramírez","doi":"10.1016/j.optlaseng.2025.109584","DOIUrl":"10.1016/j.optlaseng.2025.109584","url":null,"abstract":"<div><div>This work presents a non-iterative method for generating high-quality phase-only holograms based on the optimization of a complex field. To achieve this, an initial complex field is defined such that its product with a target amplitude yields an approximate phase-only hologram of the target after backward propagation. The complex field is then optimized using stochastic gradient descent to minimize a loss function, calculated between each hologram reconstruction and the corresponding target amplitude over a large image database. This enables the use of the optimized complex field (OCF) as a universal pre-computed function for the fast, non-iterative generation of holograms for any target. Numerical evaluations demonstrate that holograms generated with the OCF achieve superior reconstruction quality, as measured by correlation coefficient, mean squared error, and structural similarity, compared to those generated using random phase and optimized Fresnel random phase (OFRAP) methods across various epochs and propagation distances. The effectiveness of the proposed OCF method is further validated through experimental demonstrations in a holographic projection setup using a phase-only spatial light modulator.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109584"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-02DOI: 10.1016/j.optlaseng.2025.109594
Zaoxin Chen , Jiapeng Cai , Jiahao Guo , Tushar Sarkar , Dajiang Lu , Xiang Peng , Wenqi He
The dynamic-password-based Challenge-Response Protocol (CRP) is well known for its excellent ability to defend against replay attacks in authentication. However, the key unit of CRP named Dynamic Password Generator (DPG) remains susceptible to cloning attacks when the same DPG is separately stored digitally within the legitimate user and the Authentication Server’s (AS) computers. This paper tries to replace the replicable DPG with two unclonable scattering media. We suppose that Intensity-Invariant Modes (IIMs) exist between two distinct unclonable scattering media. By developing a feedback-based optimization algorithm, we anticipate that some specific identical coherent light inputs (the challenges) of two scattering media will generate nearly identical intensity outputs (the responses). In this way, the two scattering media are registered as equivalent unclonable DPGs, guaranteeing high security from contact attacks. Experimental results validated the feasibility of this approach, and a comprehensive analysis demonstrated its robustness and security.
{"title":"Scattering-media-based PUF for anti-replay authentication","authors":"Zaoxin Chen , Jiapeng Cai , Jiahao Guo , Tushar Sarkar , Dajiang Lu , Xiang Peng , Wenqi He","doi":"10.1016/j.optlaseng.2025.109594","DOIUrl":"10.1016/j.optlaseng.2025.109594","url":null,"abstract":"<div><div>The dynamic-password-based Challenge-Response Protocol (CRP) is well known for its excellent ability to defend against replay attacks in authentication. However, the key unit of CRP named Dynamic Password Generator (DPG) remains susceptible to cloning attacks when the same DPG is separately stored digitally within the legitimate user and the Authentication Server’s (AS) computers. This paper tries to replace the replicable DPG with two unclonable scattering media. We suppose that Intensity-Invariant Modes (IIMs) exist between two distinct unclonable scattering media. By developing a feedback-based optimization algorithm, we anticipate that some specific identical coherent light inputs (the challenges) of two scattering media will generate nearly identical intensity outputs (the responses). In this way, the two scattering media are registered as equivalent unclonable DPGs, guaranteeing high security from contact attacks. Experimental results validated the feasibility of this approach, and a comprehensive analysis demonstrated its robustness and security.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109594"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145876994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-06DOI: 10.1016/j.optlaseng.2025.109583
Sebastian Nilsson , Aurélien Ivanoff , Alsu Zubairova , Likitha Siddanathi , Alexey Sepman , Henrik Wiinikka , Lars-Göran Westerberg , Marcus Aldén , Christian Brackmann , Andreas Ehn
Quantitative laser-based diagnostics like Raman spectroscopy are essential for studying high-temperature processes, but their application in intensely luminous and transient environments such as plasma torches is severely limited by overwhelming background emission. This study focuses on the quantitative thermometry of a 7 kW atmospheric air plasma jet, an environment where such measurements are notoriously difficult. To enable these measurements, a Polarization Lock-In Filtering (PLF) Raman technique is used to suppress the intense and fluctuating plasma background. The method successfully yields high-quality N2 ro-vibrational spectra along the jet’s central axis. Model-based fitting of these spectra produces a detailed axial temperature profile, showing a decay from over 3700 K near the nozzle. Furthermore, the high signal quality enabled the detection of singly ionized nitrogen (N2+) in the plasma core, providing direct evidence of its ionized state. These results represent the first application of PLF for thermometry in a plasma torch and provide critical experimental data for validating magnetohydrodynamic simulations.
{"title":"Quantitative raman thermometry and N2+ detection in a non-transferred plasma torch","authors":"Sebastian Nilsson , Aurélien Ivanoff , Alsu Zubairova , Likitha Siddanathi , Alexey Sepman , Henrik Wiinikka , Lars-Göran Westerberg , Marcus Aldén , Christian Brackmann , Andreas Ehn","doi":"10.1016/j.optlaseng.2025.109583","DOIUrl":"10.1016/j.optlaseng.2025.109583","url":null,"abstract":"<div><div>Quantitative laser-based diagnostics like Raman spectroscopy are essential for studying high-temperature processes, but their application in intensely luminous and transient environments such as plasma torches is severely limited by overwhelming background emission. This study focuses on the quantitative thermometry of a 7 kW atmospheric air plasma jet, an environment where such measurements are notoriously difficult. To enable these measurements, a Polarization Lock-In Filtering (PLF) Raman technique is used to suppress the intense and fluctuating plasma background. The method successfully yields high-quality N<sub>2</sub> ro-vibrational spectra along the jet’s central axis. Model-based fitting of these spectra produces a detailed axial temperature profile, showing a decay from over 3700 K near the nozzle. Furthermore, the high signal quality enabled the detection of singly ionized nitrogen (N<sub>2</sub><sup>+</sup>) in the plasma core, providing direct evidence of its ionized state. These results represent the first application of PLF for thermometry in a plasma torch and provide critical experimental data for validating magnetohydrodynamic simulations.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109583"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-09DOI: 10.1016/j.optlaseng.2026.109614
Yiwen Feng , Jun Chang , Qinduan Zhang , Shan Lin , Yefeng Gu , Jinbao Xia , Sasa Zhang
This work presents a dual-excitation reflection enhanced laser-induced thermoelastic spectroscopy (DERE-LITES) system that advances trace gas sensing. The system employs two vacuum surface-mounted quartz tuning forks (VS-QTFs), leveraging their metallized surfaces to reflect incident beams for simultaneous dual excitation. This approach solves three critical challenges in traditional LITES gas sensing. First, VS-QTFs achieve higher Q-factors and smaller size than conventional QTFs, enabling signal amplification and sensor miniaturization. Second, the laser beam reflected from the metallized surface of the first QTF is recycled to excite the second one, dramatically improving light utilization efficiency. Third, batch-fabricated VS-QTFs maintain exceptional frequency stability, mitigating frequency mismatch and drift issues in dual-QTF systems. Experimental validation using C₂H₂ at 1530.37 nm demonstrated 1.463 times signal amplification compared to single-QTF systems. This system attained a 0.249 ppm detection limit for dual-QTF and R² = 0.998 linearity, establishing a new paradigm for high-sensitivity gas monitoring in demanding environments.
{"title":"Trace gas detection based on dual-excitation reflection enhanced laser-induced thermoelastic spectroscopy","authors":"Yiwen Feng , Jun Chang , Qinduan Zhang , Shan Lin , Yefeng Gu , Jinbao Xia , Sasa Zhang","doi":"10.1016/j.optlaseng.2026.109614","DOIUrl":"10.1016/j.optlaseng.2026.109614","url":null,"abstract":"<div><div>This work presents a dual-excitation reflection enhanced laser-induced thermoelastic spectroscopy (DERE-LITES) system that advances trace gas sensing. The system employs two vacuum surface-mounted quartz tuning forks (VS-QTFs), leveraging their metallized surfaces to reflect incident beams for simultaneous dual excitation. This approach solves three critical challenges in traditional LITES gas sensing. First, VS-QTFs achieve higher Q-factors and smaller size than conventional QTFs, enabling signal amplification and sensor miniaturization. Second, the laser beam reflected from the metallized surface of the first QTF is recycled to excite the second one, dramatically improving light utilization efficiency. Third, batch-fabricated VS-QTFs maintain exceptional frequency stability, mitigating frequency mismatch and drift issues in dual-QTF systems. Experimental validation using C₂H₂ at 1530.37 nm demonstrated 1.463 times signal amplification compared to single-QTF systems. This system attained a 0.249 ppm detection limit for dual-QTF and R² = 0.998 linearity, establishing a new paradigm for high-sensitivity gas monitoring in demanding environments.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109614"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Techniques such as fluorescence correlation spectroscopy provide quantitative assessments of molecular diffusion by analysing fluorescence intensity fluctuations over time. While they are accurate for molecular diffusion, they expect nanometric size of particles and present artifacts for larger particle sizes. Further, fluorescence labelling presents labelling imperfections and photobleaching, which restrict the accuracy of such techniques. We introduce a label-free phase correlation spectroscopy that utilizes time-resolved phase fluctuations from quantitative phase maps to determine the diffusion coefficient of micron-sized particles. Here, we first acquired the interferometric images to extract spatially sensitive quantitative phase map of the micron-sized polystyrene bead samples. These phase maps are subsequently processed to extract to diffusion parameters. In addition, the concentration dependence of the diffusion coefficient is quantified by varying particle concentrations. The results align with the Fick's second law for concentration-dependent diffusion. We believe that the present approach holds potential for various applications including biological and environmental particulate analysis.
{"title":"Phase correlation spectroscopy: a technique to quantify microparticle diffusion","authors":"Himanshu Joshi , Sunil Bhatt , Ankit Butola , Dalip Singh Mehta , Krishna Agarwal","doi":"10.1016/j.optlaseng.2026.109606","DOIUrl":"10.1016/j.optlaseng.2026.109606","url":null,"abstract":"<div><div>Techniques such as fluorescence correlation spectroscopy provide quantitative assessments of molecular diffusion by analysing fluorescence intensity fluctuations over time. While they are accurate for molecular diffusion, they expect nanometric size of particles and present artifacts for larger particle sizes. Further, fluorescence labelling presents labelling imperfections and photobleaching, which restrict the accuracy of such techniques. We introduce a label-free phase correlation spectroscopy that utilizes time-resolved phase fluctuations from quantitative phase maps to determine the diffusion coefficient of micron-sized particles. Here, we first acquired the interferometric images to extract spatially sensitive quantitative phase map of the micron-sized polystyrene bead samples. These phase maps are subsequently processed to extract to diffusion parameters. In addition, the concentration dependence of the diffusion coefficient is quantified by varying particle concentrations. The results align with the Fick's second law for concentration-dependent diffusion. We believe that the present approach holds potential for various applications including biological and environmental particulate analysis.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"200 ","pages":"Article 109606"},"PeriodicalIF":3.7,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-05-01Epub Date: 2026-01-10DOI: 10.1016/j.optlaseng.2026.109617
Haozhen Huang , Yuezhe Zhang , Limei Song
The accuracy of phase calculation is critical to achieving high-precision three-dimensional reconstruction in fringe projection profilometry. In conventional multi-frequency heterodyne methods, the phase-solving accuracy depends on the highest-frequency fringe, while the low-frequency fringes used for auxiliary unwrapping do not contribute to accuracy, resulting in wasted information. To address this, this paper proposes an absolute phase post-processing optimization algorithm, the core of which is to formulate the phase optimization problem as a loss minimization problem based on a differentiable forward model. First, the initial absolute phase is obtained using the standard multi-frequency heterodyne method. Then, by inversely mapping the absolute phase back to the wrapped phase domain, the residual between the synthesized and the observed fringe patterns is constructed, leading to a unified, fully differentiable objective function that integrates multi-frequency information and enables joint parameter coupling. Finally, a multi-parameter iterative optimization framework is employed, in which the absolute phase, background intensity, and modulation intensity of each pixel are jointly optimized through analytical gradient computation and iterative updates. Experimental results demonstrate that the proposed method effectively exploits all fringe information and significantly suppresses phase unwrapping errors. The root mean square error (RMSE) of the fitted standard plane measurements is reduced by >20% on average compared with the traditional three-step and six-step phase-shifting methods, while the measurement accuracy of the fitted standard sphere diameter is improved by over 30% on average relative to these conventional methods.
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