Optics lettersPub Date : 2025-06-01DOI: 10.1364/OL.561929
Jin Sun, Ying He, Shunda Qiao, Chu Zhang, Yufei Ma
{"title":"Acetylene-enhanced methane-QEPAS sensing.","authors":"Jin Sun, Ying He, Shunda Qiao, Chu Zhang, Yufei Ma","doi":"10.1364/OL.561929","DOIUrl":"https://doi.org/10.1364/OL.561929","url":null,"abstract":"<p><p>Methane (CH<sub>4</sub>), as a critical greenhouse gas and explosive hazard, demands highly sensitive detection for environmental monitoring and industrial safety. To address the limitation of its slow relaxation in quartz-enhanced photoacoustic spectroscopy (QEPAS), this paper reported a novel acetylene (C<sub>2</sub>H<sub>2</sub>)-enhanced QEPAS technique for CH<sub>4</sub> sensing for the first time to our knowledge. Unlike the commonly used catalyst of water vapor (H<sub>2</sub>O), whose concentration in the air frequently changes and causes fluctuations in both the QEPAS signal level and the characteristics of the quartz tuning fork (QTF), C<sub>2</sub>H<sub>2</sub> accelerates CH<sub>4</sub> relaxation without inducing significant shifts in the QTF frequency. Firstly, the catalytic effect of C<sub>2</sub>H<sub>2</sub> molecules on the CH<sub>4</sub> relaxation process was analyzed. Systematic investigations revealed that increasing C<sub>2</sub>H<sub>2</sub> concentration enhances CH<sub>4</sub>-QEPAS signal intensity in three distinct phases: rapid growth, gradual saturation, and eventual stabilization. At 6000 ppm C<sub>2</sub>H<sub>2</sub>, the CH<sub>4</sub>-QEPAS signal amplitude increased by 2.53-fold compared to the situation without C<sub>2</sub>H<sub>2</sub>. The C<sub>2</sub>H<sub>2</sub>-enhanced CH<sub>4</sub>-QEPAS system maintained excellent linearity (R<sup>2</sup> = 0.9999) across 1000-12,000 ppm CH<sub>4</sub>. Allan deviation analysis confirmed a minimum detection limit (MDL) of 540 ppb at 1000 s average time, demonstrating excellent long-term stability. This work not only provides a robust strategy for CH<sub>4</sub> detection but also expands the application of QEPAS in gas relaxation dynamics modulation, highlighting C<sub>2</sub>H<sub>2</sub> as a superior relaxation promoter for other molecules with a slow relaxation rate.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3760-3763"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Decoupling of nanoindentation residual stress field in single-crystalline 4H-SiC via micro-Raman spectroscopy.","authors":"Zhoudong Yang, Jing Tian, Xinyue Wang, Junwei Chen, Yuanhui Zuo, Rongjun Zhang, Hongyu Tang, Xuejun Fan, Guoqi Zhang, Jiajie Fan","doi":"10.1364/OL.563213","DOIUrl":"https://doi.org/10.1364/OL.563213","url":null,"abstract":"<p><p>This Letter presents a combined analytical and experimental method to effectively decouple the radial and tangential residual stress fields induced by Berkovich nanoindentation in single-crystalline 4H-SiC using micro-Raman spectroscopy. By integrating the Raman stress characterization model with Yoffe's expanding cavity model, precise extraction of individual residual stress components around the indentation region is realized. Through the vertical backscattering micro-Raman mapping of the E<sub>2</sub> phonon mode, we systematically investigate the residual stress distribution near the indentation. The results highlight significant anisotropy in nanoindentation-induced stress fields, strongly dependent on the crystal orientation of 4H-SiC, predominantly featuring radial tensile stress gradients. This comprehensive theoretical-experimental approach offers a robust optical framework for residual stress characterization in 4H-SiC and provides foundational insights for extending Raman spectroscopy-based stress characterization to other crystalline materials and related device structures.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3513-3516"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Erbium-doped lithium niobate waveguide amplifier enhanced by an inverse-designed on-chip reflector.","authors":"Zhiwei Wei, Jiangwei Wu, Chengyu Chen, Hao Li, Wenjie Wan, Xianfeng Chen, Yuping Chen","doi":"10.1364/OL.561831","DOIUrl":"https://doi.org/10.1364/OL.561831","url":null,"abstract":"<p><p>This study presents a 3.6-cm-long erbium-doped lithium niobate waveguide amplifier enhanced by an inverse-designed on-chip reflector. Integrating a reflector to reflect signal light (1531.6 nm) at the waveguide end yielded an internal net gain of 40.5 dB, achieving a 17.3 dB gain improvement compared to a comparable reflector-free amplifier under small signal conditions. These results highlight a novel strategy, to the best of our knowledge, for optimizing integrated optical amplifiers, combining high gain with simplified architecture. The approach holds promise for advancing high-density photonic integrated systems, demonstrating the efficacy of inverse design in tailoring photonic device performance for practical applications.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3624-3627"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"High-speed low-noise InGaAs/InP PIN photodetectors on a Si platform achieved by oxygen plasma activation bonding.","authors":"Wenhao Meng, Xiaolong Jiang, Menghui Guo, Zhanren Wang, Yiliang Diao, Zhiwei Huang, Jinrong Zhou, Guanzhou Liu, Xiaoying Zhang, Shaoying Ke","doi":"10.1364/OL.559090","DOIUrl":"https://doi.org/10.1364/OL.559090","url":null,"abstract":"<p><p>In this paper, we report the hydrophilic wafer bonding of a 2 in. InP-based InGaAs/InP epitaxial film to a SiO<sub>2</sub>/Si substrate using oxygen plasma surface activation. The fabricated vertical Si-based InGaAs/InP PIN photodetectors exhibit an exceptionally low surface leakage current of 2.32 nA/cm and a bulk leakage current of 37.47 nA/cm<sup>2</sup> at -1 V. The device with a diameter of 13 μm achieves a remarkable 3 dB bandwidth of 30.453 GHz. Furthermore, the 70 μm diameter device has a response rate of 0.87 A/W and 0.58 A/W at 1370 nm and 1660 nm, respectively.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3549-3552"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optics lettersPub Date : 2025-06-01DOI: 10.1364/OL.558636
Dharma P Permana, Yvan Klaver, Alexander A Iskandar, David Marpaung
{"title":"Kerr nonlinear coefficient measurement of low-loss double-stripe silicon nitride waveguides.","authors":"Dharma P Permana, Yvan Klaver, Alexander A Iskandar, David Marpaung","doi":"10.1364/OL.558636","DOIUrl":"https://doi.org/10.1364/OL.558636","url":null,"abstract":"<p><p>Multi-layer Si<sub>3</sub>N<sub>4</sub> waveguides, also known as Triplex waveguide technology, are a very promising waveguide platform for applications in microwave photonics and quantum photonics due to their low loss and compact circuit footprint. However to date, the Kerr nonlinearity of these multi-layer waveguides, in particular the asymmetric double-stripe (ADS) Si<sub>3</sub>N<sub>4</sub> waveguides, has not been well-investigated. Here, we performed an experimental investigation of the Kerr nonlinearity of ADS Si<sub>3</sub>N<sub>4</sub> waveguides through four-wave mixing (FWM) experiments. We obtained the nonlinear coefficient for this waveguide to be <i>γ</i><sub>ADS</sub> = 0.336 ± 0.023 W<sup>-1</sup>m<sup>-1</sup>. When combined with low propagation loss and absence of two-photon absorption, this moderate nonlinearity can be harnessed for chip-based nonlinear signal processing and quantum photonics.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3616-3619"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Low-loss ultra-large mode area all-solid chalcogenide photonic crystal fiber for 20 W level mid-infrared laser delivery.","authors":"Chong Wang, Tiankai Hou, Yantao Xu, Yanjie Chang, Hao Zhang, Haitao Guo","doi":"10.1364/OL.557304","DOIUrl":"https://doi.org/10.1364/OL.557304","url":null,"abstract":"<p><p>To achieve mid-infrared high-power laser delivery, a single-mode large mode area (∼9900 µm<sup>2</sup>) all-solid photonic crystal fiber (AS-PCF) based on As<sub>2</sub>Se<sub>3</sub> and As<sub>2</sub>S<sub>3</sub> chalcogenide glasses was designed. The finite element method was used to study the influence of structural parameters on the optical properties of the fiber. The AS-PCF was fabricated by the stacking-drawing method after material purification, and the optical loss, the near-field mode distributions, and the high-power laser transmission were measured. The fiber exhibits a minimum loss of 4.62 dB/m, which is the lowest loss among chalcogenide AS-PCF on record, and it can carry at least 20 W of high-power transmission, demonstrating strong potential for mid-infrared laser delivery applications.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3696-3699"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optics lettersPub Date : 2025-06-01DOI: 10.1364/OL.562278
Yi Wang, Shuna Yang, Bo Yang, Yiran Gao, Hao Chi
{"title":"Photonic real-time Fourier transform via optical phase conjugation.","authors":"Yi Wang, Shuna Yang, Bo Yang, Yiran Gao, Hao Chi","doi":"10.1364/OL.562278","DOIUrl":"https://doi.org/10.1364/OL.562278","url":null,"abstract":"<p><p>We propose a novel approach, to our knowledge, for implementing photonic real-time Fourier transform (RTFT) based on optical phase conjugation, which enables the spectral content of an input microwave signal to be mapped onto the time-domain waveform of output pulses. In the approach, the phase-conjugated signal is generated via four-wave mixing in a semiconductor optical amplifier, and frequency-to-time mapping is performed using two identical dispersive elements (DEs). This configuration effectively maps the spectrum of the input microwave signal to the output time-domain waveform, removing the requirement for DEs with opposite dispersion signs, which are typically required in conventional RTFT systems. The feasibility of this RTFT approach for microwave frequency measurement is validated through an experiment utilizing modulated pulses, phase conjugation, and two identical DEs, with the frequency resolution reaching the theoretical limit determined by the electrical bandwidth and the dispersion amount of the system.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3632-3635"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optics lettersPub Date : 2025-06-01DOI: 10.1364/OL.557384
Zhizheng Wang, Mohsin Raza, Bin Zhou, Nan Wang, Kummara Venkata Krishnaiah, Yuwen Qin, A Ping Zhang
{"title":"3D micro-printed polymer limacon-shaped whispering-gallery-mode microlaser sensors for label-free biodetection.","authors":"Zhizheng Wang, Mohsin Raza, Bin Zhou, Nan Wang, Kummara Venkata Krishnaiah, Yuwen Qin, A Ping Zhang","doi":"10.1364/OL.557384","DOIUrl":"https://doi.org/10.1364/OL.557384","url":null,"abstract":"<p><p>Optical whispering-gallery-mode (WGM) microlaser sensors have garnered significant attention in biological sensing due to their distinct advantages, including strong light-matter interactions and versatile sensing modalities. However, challenges remain in developing WGM microlaser sensors that can serve as building blocks for large-scale integrated sensor platforms in lab-on-chip applications. In this work, we present a 3D micro-printed polymer limacon-shaped WGM microlaser sensor for on-chip integrated biosensing. The WGM microlaser sensor has both high-quality factor (<i>Q</i> factor) and directional emission properties, making it ideal for high-sensitive on-chip biosensing platforms using a far-field coupling scheme. Experimental results showed that the 3D micro-printed WGM laser sensor has a very low lasing threshold of 3.87 µJ/mm<sup>2</sup> and a narrow lasing linewidth of about 30 pm. Remarkably, experiments have shown that the sensor can detect human IgG with a detection limit of around 70 ag/mL, revealing its potential for ultralow-limit detection of biomarkers in early disease diagnosis.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3481-3484"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Bandwidth-enhanced LFM signal generation by period-one dynamics in a directly modulated semiconductor laser.","authors":"Gengze Wu, Fangzheng Zhang, Xiaoyue Yu, Xin Yan, Hao Wang, Yuan Yu, Shilong Pan","doi":"10.1364/OL.559656","DOIUrl":"https://doi.org/10.1364/OL.559656","url":null,"abstract":"<p><p>Period-one (P1) laser dynamics provide effective methods for radar signal generation. However, the linearly frequency-modulated (LFM) signal bandwidth generated by P1 dynamics is constrained by the limited variation range of the injection strength. In this Letter, a bandwidth-enhanced LFM signal generation method by P1 dynamics in an optically injected directly modulated semiconductor laser (DM-SL) is proposed. In addition to controlling the injection strength via electro-optical modulation, which is the same as the previous schemes, the bias current of the DM-SL is regulated via direct modulation. By interaction between the carrier effect and temperature effect in the optically injected DM-SL, the P1 oscillation frequency is increased under the same optical injection strength, leading to the generation of LFM signals with enlarged bandwidth. In the experiment, the maximum signal bandwidth reaches 21 GHz (11.7-32.7 GHz), which is enhanced by 11 GHz compared with that generated without bias current regulation. The proposed method is a promising technique for ultra-wideband radar signal generators.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3572-3575"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optics lettersPub Date : 2025-06-01DOI: 10.1364/OL.561695
Zhenzhen Yu, Xiaoming Li, Min Li, Jinxing Zhao, Peng Wang, Dawei Wang, Jinxin Zhao, Li Guan, Xu Li
{"title":"Boric acid additive strategy for improving the performance of carbon dot-based light-emitting diodes.","authors":"Zhenzhen Yu, Xiaoming Li, Min Li, Jinxing Zhao, Peng Wang, Dawei Wang, Jinxin Zhao, Li Guan, Xu Li","doi":"10.1364/OL.561695","DOIUrl":"https://doi.org/10.1364/OL.561695","url":null,"abstract":"<p><p>Carbon dots (CD)-based light-emitting diodes (LEDs) with low cost, easy acquisition, and environmental friendliness are an emerging display technology worth further exploration. However, it is still a challenge to prepare CD-based LEDs with high performance and spectral modulation. In this study, green-emitting CDs (G-CDs) were prepared into LEDs by the traditional solution method. These G-CD-based LEDs reach maximum brightness and external quantum efficiency of 400 cd/m<sup>2</sup> and 0.02%, respectively. By further introducing boric acid into G-CDs, yellow emitting carbon dots (Y-CDs) were successfully prepared. This additive engineering achieves spectral modulation, and the maximum brightness and external quantum efficiency are close to 2 times and 3 times that of the control device. This study shows the potential of boric acid in optimizing the performance of CD-based LEDs.</p>","PeriodicalId":19540,"journal":{"name":"Optics letters","volume":"50 11","pages":"3712-3715"},"PeriodicalIF":3.1,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}