Applied optics最新文献

{"title":"Comparative study of laser-induced damage on deep ultraviolet high-reflection coatings with protective layers.","authors":"Enlong Wang, Xi Wang, Hao Zhang, Xin Li","doi":"10.1364/AO.606920","DOIUrl":"https://doi.org/10.1364/AO.606920","url":null,"abstract":"<p><p>Deep ultraviolet (DUV) lasers, particularly at 193 and 248 nm, are critical for applications such as photolithography and inertial confinement fusion. However, the high-power operation required in these systems induces damage to high-reflection (HR) coatings, a challenge that remains not fully understood in the DUV regime due to limitations in laser sources and deposition technologies. This work presents a systematic and comparative study on the laser-induced damage mechanisms of HR coatings with protective layer under nanosecond DUV laser pulses. Theoretical models incorporating standing-wave electric field distribution, thermomechanical stress, and the effects of defects are developed. Comparative experiments are conducted on dielectric HR coatings exposed to 193 nm (25 ns) and 248 nm (13 ns) excimer lasers, evaluating damage thresholds, morphologies, and the protective role of capping layers. Results show that damage progresses incrementally with increasing laser pulse fluence and count. Among the coatings studied, the LaF₃/AlF₃ HR coating exhibits better damage resistance compared to the Al₂O₃/MgF₂ coating. The application of a MgF₂ protective layer markably enhances the damage threshold by shifting the peak standing-wave electric field forward, thereby reducing absorption in the uppermost high-index layer. These findings provide critical insights into DUV laser damage mechanisms, offer practical guidance for HR coating selection, and establish a reference for future studies on DUV laser-induced damage.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10143-10153"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the use of Sanderson prisms for variable beam separation FLDI applications.","authors":"Alexandre R Berger, Elizabeth K Benitez, Matthew P Borg","doi":"10.1364/AO.610595","DOIUrl":"https://doi.org/10.1364/AO.610595","url":null,"abstract":"<p><p>The effect of variable beam separation on the performance of focused laser differential interferometry (FLDI) in detecting second-mode instabilities is investigated experimentally using what we believe to be a novel co-linear Sanderson prism-based FLDI and schlieren system. Experiments are conducted in a Mach-6 Ludwieg Tube on a 7° cone with a sharp nose tip. Beam separations of 100, 150, 250, and 400 µm are tested. The 250 µm case provides the clearest spectral peaks, highest coherence, and highest in-band to out-of-band root-mean-square (RMS) amplitude ratio. Overall, diagnostic performance improves with increasing beam separation, consistent with trends predicted by previous FLDI simulations. The reduced performance for the 400 µm separation is attributed to its lower position within the boundary layer. These results illustrate the importance of matching beam separation to the relevant flow structure scales.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10223-10234"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhanced UV photodetection of Ag-decorated GaN/Si heterojunctions prepared by pulsed laser ablation in liquid and hydrothermal deposition.","authors":"Rawan B Fadhil, Evan T Salim, Subash C B Gopinath, Motahher A Qaeed","doi":"10.1364/AO.613902","DOIUrl":"https://doi.org/10.1364/AO.613902","url":null,"abstract":"<p><p>In this study, GaN nanoparticles were synthesized by pulsed laser ablation in liquid (PLAL) followed by hydrothermal deposition. Different AgNO₃ concentrations were comparatively investigated to determine the optimum amount for fabricating the Ag-decorated GaN/Si UV photodetector. Among the investigated amounts, the sample prepared using 0.01 g AgNO₃ exhibited the highest figure of merit and was therefore selected for detailed characterization and device fabrication. Ag diffraction peaks and the hexagonal wurtzite GaN phase were confirmed by XRD investigation. Optical measurements showed a bandgap of 3.37 eV. FESEM and AFM analyses revealed a uniform distribution of Ag nanoparticles, indicating successful surface modification. Based on these improved physical properties, the Ag-decorated GaN/Si heterojunction photodetector was fabricated, exhibiting enhanced responsivity, detectivity, and overall UV-photodetection performance. The Ag-decorated device exhibited improved electrical performance and higher responsivity and detectivity at 380 nm compared with the pure GaN/Si device. The ideality factor (n) was reduced to 1.6 for the Ag-decorated GaN/Si heterojunction device. The faster response of the Ag-decorated GaN/Si device demonstrates its potential for fast-switching optoelectronic applications.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10265-10274"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Continuously tunable attenuation stage for weak-light radiance calibration using an integrating sphere and a dual-aperture tube.","authors":"Wentao Wang, Jianjun Li, Qing Kang, Xiaobing Zheng","doi":"10.1364/AO.612091","DOIUrl":"https://doi.org/10.1364/AO.612091","url":null,"abstract":"<p><p>We present a continuously tunable weak-light attenuation stage combining an integrating sphere with a coaxial dual-aperture tube. An exact view-factor model provides the geometry-based reference, and a monitor-normalized calibration produced a 22×22 attenuation matrix spanning 0-40.36 dB. A separable correction reduced the in-grid residual RMS to 0.017 dB. Independent target-setting validation over 5.0-39.1 dB yielded an RMS residual of 0.091 dB. Measured spatial and angular departures of the input field were propagated into the uncertainty budget, giving an expanded uncertainty of 0.021-0.036 dB (<i>k</i>=2). Spectral-shape RMS deviations remained within 0.477% up to 15 dB.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10076-10087"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robust trajectory triangulation for UAV visual localization via iteratively reweighted least squares.","authors":"Yinbo Xu, Zhijian Xiao, Jiarun Yan, Yangguang Yu, Xiangke Wang","doi":"10.1364/AO.611569","DOIUrl":"https://doi.org/10.1364/AO.611569","url":null,"abstract":"<p><p>Accurate localization of ground targets using monocular vision from a fixed-wing unmanned aerial vehicle (UAV) in tracking mode is a challenging problem in computer vision and photogrammetry. Classical triangulation methods often suffer from rank deficiency due to degenerate observation geometry. The trajectory triangulation paradigm overcomes this limitation by parameterizing target motion, yet existing solvers typically assume Gaussian-distributed observation noise with uniform weights, making them vulnerable to non-uniform noise induced by the UAV's high-speed maneuvering and to image matching outliers. This paper proposes a robust trajectory triangulation algorithm based on iteratively reweighted least squares. The proposed method constructs a target motion model tailored to the fixed-wing UAV's viewing geometry and incorporates robust M-estimation kernel functions, transforming the optimization into a sequence of adaptively weighted subproblems. The algorithm dynamically adjusts the weight of each observation ray according to its residual magnitude, effectively suppressing outlier interference while preserving computational efficiency. Experiments on numerical simulation and Gazebo simulation demonstrate that the proposed method outperforms baseline linear solvers and nonlinear least-squares optimizers in localization accuracy, especially in challenging circling tracking scenarios characterized by high dynamics and noise, reducing the mean localization RMSE by 75.8% and 68.3% compared with the baseline linear solver and the nonlinear least-squares optimizer, respectively.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10094-10106"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Classification of camouflage-coated samples using a compact spectral Mueller-matrix descriptor.","authors":"Zhiyong Yang, Guangchen Wang, Zhiwei Zhang, Wei Cai, Enqing Chen","doi":"10.1364/AO.612694","DOIUrl":"https://doi.org/10.1364/AO.612694","url":null,"abstract":"<p><p>Reliable classification of camouflage-coated samples is relevant to optical inspection and material characterization, but samples with similar visible appearance may exhibit overlapping intensity responses and remain difficult to distinguish. Spectral Mueller matrices provide additional information on polarization transfer; however, directly using the full matrix spectra produces high-dimensional inputs, whereas individual polarimetric parameters describe only limited aspects of the coating response. This work proposes a 12-feature polarization-retention and coupling spectral-moment descriptor derived from white-reference-normalized spectral Mueller matrices (WPRC-SM12). The descriptor combines the white-reference-normalized intensity response, diagonal-retention mean coordinate, diagonal-retention anisotropy magnitude, and selected <i>U</i>-<i>V</i> coupling magnitude and summarizes the level, first-order trend, and second-order curvature of each component using low-order spectral moments. A dataset of 1620 measurements was acquired from nine classes of camouflage-coated samples over 510-800 nm under 12 incidence-reflection geometries. The proposed descriptor and five baseline descriptors were evaluated using nested grouped cross-validation, a fixed incidence-angle hold-out test, and leave-one-geometry-out validation. Under nested grouped cross-validation, WPRC-SM12 combined with LDA achieved an accuracy of 93.52% and a macro-F1 score of 93.50%. Across the five evaluated classifier pipelines, WPRC-SM12 also achieved the highest mean accuracy. For WPRC-SM12, linear SVM achieved an accuracy of 90.00% in the fixed 50° incidence-angle hold-out test. Under leave-one-geometry-out validation, LDA yielded an aggregate accuracy of 95.80% and a macro-F1 score of 95.78%. The remaining errors were concentrated in a limited number of sample classes and showed class-dependent sensitivity to broader changes in measurement geometry. These results demonstrate that WPRC-SM12 provides a compact and physically interpretable feature representation for the classification of camouflage-coated samples. The geometry hold-out results further suggest that representative angular coverage during model development can improve classification consistency.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10115-10127"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Retrieval of the polarization gain ratio for polarization lidar using a hybrid data method.","authors":"Houtong Liu, Qi Zhang, Qingbang Shu, Gensheng Zha, Xianguo Meng","doi":"10.1364/AO.611733","DOIUrl":"https://doi.org/10.1364/AO.611733","url":null,"abstract":"<p><p>In cirrus conditions, the polarization gain ratio of a polarization lidar can be accurately determined using the hybrid data method, which relies on two sets of detection data: one obtained under a known polarization gain ratio and the other under an unknown ratio. From the extensive measurements acquired between January 2005 and January 2008 using a polarization-Mie scattering lidar equipped with a polarization gain ratio measurement unit, 10 datasets were selected based on their suitability for retrieving the polarization gain ratio via the hybrid data method. In addition, the corresponding gain ratios for these datasets were measured by the lidar's built-in gain ratio measurement unit. The gain ratios derived from the hybrid method were subsequently compared with those obtained using a polarization calibration device; the maximum discrepancy between the two methods was found to be 0.01. It is evident that, within a certain period following a single polarization gain ratio calibration, the hybrid data method can yield an accurate polarization gain ratio for the corresponding datasets. However, the polarization gain ratio obtained through this method is susceptible to the influence of aerosol changes around the cirrus layer.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10107-10114"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic optical response of a self-referenced multi-defect photonic crystal under modeled tear-film perturbations: a photonic modeling framework for ocular-surface analysis.","authors":"Asala Bakry, Fatma A Sayed, Rafat M Amin, Arafa H Aly","doi":"10.1364/AO.610390","DOIUrl":"https://doi.org/10.1364/AO.610390","url":null,"abstract":"<p><p>A transfer-matrix framework is developed for dynamic optical fingerprinting of modeled tear-film perturbations using a thermally self-referenced multi-defect one-dimensional photonic crystal. Four coupled defect compartments represent aqueous-index variation, hydration-dependent optical-thickness change, mucin/inhomogeneity-associated loss, and lipid-composite evolution, while a sealed reference cavity compensates common-mode thermal drift. Time-dependent transmission spectra are analyzed using corrected defect-mode shifts and local peak-transmission changes. The resulting hybrid fingerprints distinguish stable-film-like, evaporation-dominant-like, aqueous-deficient-like, lipid-deficient-like, and mucin-instability-like scenarios. The minimum terminal uncertainty-normalized separation was 16.43, exceeding the prescribed threshold of 3, and remained above this threshold from t=0.4 s onward using a 0.10 s sampling interval. Monte Carlo analysis with 500 realizations yielded a terminal minimum separation of 17.19±2.35, with all realizations exceeding the threshold. Under the matched-model thermal-only blank, temperature calibration suppresses simulated thermal drift by 99.85%-99.98%. These results establish a numerically grounded self-referenced framework for analyzing time-varying tear-film-like perturbations.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10212-10222"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robustness-enhanced optical coverless hiding scheme for UAV images based on linear canonical transform and mapping features.","authors":"Yonggang Su, Liang Qi, Wenjun Xu","doi":"10.1364/AO.604332","DOIUrl":"https://doi.org/10.1364/AO.604332","url":null,"abstract":"<p><p>Current optical image encryption and hiding methods generally suffer from weak robustness in the face of various attacks and transmission channel interference, which severely restricts their engineering application. In addition, existing embedded optical image hiding methods require modification of the carrier image, leading to limited embedding capacity and the risk of plaintext information leakage during the storage and transmission of the stego-carrier. Furthermore, there are few reports in the literature on optical encryption and hiding of UAV aerial images to date. To address these issues, this paper proposes what is believed to be a novel robust-enhanced optical coverless hiding method for UAV aerial images. In the proposed hiding method, bimodal biometric keys are first generated using face and palmprint images. Subsequently, the UAV aerial image is subjected to scrambling and zero-padding, followed by an encryption process performed sequentially through a cascaded Fresnel transform, a biometric mask, and a linear canonical transform. To achieve coverless hiding, a robust feature sequence is extracted from the carrier image, and the real and imaginary parts of the optically encrypted complex amplitude, after scrambling and diffusion, are subjected to XOR mapping to generate a mapping key, thereby realizing coverless hiding. Extensive numerical simulation results demonstrate that the proposed hiding method not only exhibits strong security and robustness against conventional attacks but also shows high reliability and robustness in practical communication systems such as OFDM and GFDM.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"9976-9986"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Longwave infrared snapshot spectrometer for chemical vapor identification.","authors":"William G Lawrence","doi":"10.1364/AO.607408","DOIUrl":"https://doi.org/10.1364/AO.607408","url":null,"abstract":"<p><p>Snapshot spectrometers are a class of optical sensors in which the spectral resolution element is coupled to a camera focal plane detector array, and all the information required for the measurement of the spectrum is acquired in a single camera image. This work presents the development and characterization of a longwave infrared (LWIR) snapshot spectrometer that has been applied to the identification of chemical vapors. The spectral resolution of the sensor is provided by a 24×32 element array of Fabry-Perot filters. Complementary metal oxide semiconductor (CMOS) fabrication methods were used to create the filter array. Gray scale lithography was used to pattern a germanium layer to form Fabry-Perot filters with different cavity spacings that transmit different wavelength bands. The fabricated filter had an operational wavelength range from 7.8 to 11.2 µm. The process window for the wafer fabrication achieved 315 filter elements at 63 different center wavelengths. Details of the fabrication and characterization of the snapshot filter are presented. The application of the snapshot spectrometer for the identification and discrimination of chemical vapors is demonstrated for 1,1-difluoroethane, methanol, and sulfur hexafluoride. The concentration-path length limit of detection for these gases was 1.7, 3.1, and 0.4 mg/m², respectively.</p>","PeriodicalId":101299,"journal":{"name":"Applied optics","volume":"65 29","pages":"10154-10167"},"PeriodicalIF":0.0,"publicationDate":"2026-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149229513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}