We propose an all-optical approach to generating space–time wave packets in a multimode slab waveguide via the multilevel interband stimulated Brillouin scattering process. Two pump sources and a single-mode signal are fed into the waveguide. The pumps generate a single-mode acoustic wave through the electrostrictive process. The acoustic wave then induces an indirect interband photonic transition from the signal wave, resulting in a light bullet, that is, a space–time wave packet that does not change its spatial and temporal shape as it propagates through the waveguide.
{"title":"Light bullet generation via stimulated Brillouin scattering","authors":"Der-Han Huang, Cheng Guo, Shanhui Fan","doi":"10.1063/5.0201756","DOIUrl":"https://doi.org/10.1063/5.0201756","url":null,"abstract":"We propose an all-optical approach to generating space–time wave packets in a multimode slab waveguide via the multilevel interband stimulated Brillouin scattering process. Two pump sources and a single-mode signal are fed into the waveguide. The pumps generate a single-mode acoustic wave through the electrostrictive process. The acoustic wave then induces an indirect interband photonic transition from the signal wave, resulting in a light bullet, that is, a space–time wave packet that does not change its spatial and temporal shape as it propagates through the waveguide.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"15 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141517033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Pattern-illuminated Fourier ptychography (piFP) is an elegant combination of structured illumination imaging and a Fourier ptychographic algorithm with the ability to image beyond the diffraction limit of the employed optics. Artifact-free piFP super-resolution reconstruction requires a high level of stability in the illumination pattern. However, unpredictable pattern variation occurs in the presence of environment perturbation, intensity fluctuation, and pointing instability at the source, leading to declines in image reconstruction quality. To address this issue, we present an efficient and robust piFP algorithm based on low-rank approximation (LRA-piFP), which relaxes the requirement for the stability of illumination patterns. This LRA-piFP method can model frame-wise pattern variation during a full scan, thus improve the reconstruction quality significantly. We take numerical simulations and proof-of-principle experiments with both long-range imaging and microscopy for demonstrations. Results show that the LRA-piFP method can handle different kinds of pattern variation and outperforms other state-of-the-art techniques in terms of reconstruction quality and resolution improvement. Our method provides effective experimental robustness to piFP with a natural algorithmic extension, paving the way for its application in both macroscopic and microscopic imaging.
{"title":"Toward robust super-resolution imaging: A low-rank approximation approach for pattern-illuminated Fourier ptychography","authors":"Junhao Zhang, Weilong Wei, Kaiyuan Yang, Qiang Zhou, Haotong Ma, Ge Ren, Zongliang Xie","doi":"10.1063/5.0200549","DOIUrl":"https://doi.org/10.1063/5.0200549","url":null,"abstract":"Pattern-illuminated Fourier ptychography (piFP) is an elegant combination of structured illumination imaging and a Fourier ptychographic algorithm with the ability to image beyond the diffraction limit of the employed optics. Artifact-free piFP super-resolution reconstruction requires a high level of stability in the illumination pattern. However, unpredictable pattern variation occurs in the presence of environment perturbation, intensity fluctuation, and pointing instability at the source, leading to declines in image reconstruction quality. To address this issue, we present an efficient and robust piFP algorithm based on low-rank approximation (LRA-piFP), which relaxes the requirement for the stability of illumination patterns. This LRA-piFP method can model frame-wise pattern variation during a full scan, thus improve the reconstruction quality significantly. We take numerical simulations and proof-of-principle experiments with both long-range imaging and microscopy for demonstrations. Results show that the LRA-piFP method can handle different kinds of pattern variation and outperforms other state-of-the-art techniques in terms of reconstruction quality and resolution improvement. Our method provides effective experimental robustness to piFP with a natural algorithmic extension, paving the way for its application in both macroscopic and microscopic imaging.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"145 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141528919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
The statistical mechanical behavior of weakly nonlinear multimoded optical settings has been attracting increased interest over the last few years. The main purpose of this work is to numerically investigate the main factors that affect the thermalization process in photonic lattices. In particular, we find that lattices with identically selected properties (such as temperature, coupling coefficient, lattice size, and excitation conditions) can exhibit very different thermalization dynamics and, thus, thermalization distances. Our investigation is focused on two different two-dimensional lattices: the honeycomb lattice and the triangular lattice. Our numerical results show that, independently of the excitation conditions, the honeycomb lattice always thermalizes faster than the triangular lattice. We mainly explain this behavior by the quasilinear spectrum that promotes wave-mixing in the honeycomb lattice in comparison to the power-like spectrum of the triangular lattice. In addition, we investigate the combined effects of temperature as well as the sign and magnitude of the nonlinearity. Switching either the sign of the Kerr nonlinear coefficient or the sign of the temperature can lead to significant differences in the thermalization dynamics, a phenomenon that can be physically explained in terms of wave instabilities. Larger absolute values of the temperature |T| result in more uniform distributions for the power occupation numbers and faster thermalization speeds. Finally, as expected, increasing the magnitude of the nonlinearity results in accelerated thermalization. Our findings provide valuable insights into optical thermalization in discrete systems, where experimental realization may bring about new possibilities for light manipulation and applications.
{"title":"Thermalization dynamics in photonic lattices of different geometries","authors":"Guowen Yang, Domenico Bongiovanni, Daohong Song, Roberto Morandotti, Zhigang Chen, Nikolaos K. Efremidis","doi":"10.1063/5.0205202","DOIUrl":"https://doi.org/10.1063/5.0205202","url":null,"abstract":"The statistical mechanical behavior of weakly nonlinear multimoded optical settings has been attracting increased interest over the last few years. The main purpose of this work is to numerically investigate the main factors that affect the thermalization process in photonic lattices. In particular, we find that lattices with identically selected properties (such as temperature, coupling coefficient, lattice size, and excitation conditions) can exhibit very different thermalization dynamics and, thus, thermalization distances. Our investigation is focused on two different two-dimensional lattices: the honeycomb lattice and the triangular lattice. Our numerical results show that, independently of the excitation conditions, the honeycomb lattice always thermalizes faster than the triangular lattice. We mainly explain this behavior by the quasilinear spectrum that promotes wave-mixing in the honeycomb lattice in comparison to the power-like spectrum of the triangular lattice. In addition, we investigate the combined effects of temperature as well as the sign and magnitude of the nonlinearity. Switching either the sign of the Kerr nonlinear coefficient or the sign of the temperature can lead to significant differences in the thermalization dynamics, a phenomenon that can be physically explained in terms of wave instabilities. Larger absolute values of the temperature |T| result in more uniform distributions for the power occupation numbers and faster thermalization speeds. Finally, as expected, increasing the magnitude of the nonlinearity results in accelerated thermalization. Our findings provide valuable insights into optical thermalization in discrete systems, where experimental realization may bring about new possibilities for light manipulation and applications.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"36 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141516978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Kabish Wisal, Chun-Wei Chen, Hui Cao, A. Douglas Stone
Transverse Mode Instability (TMI) that results from dynamic nonlinear thermo-optical scattering is the primary limitation to power scaling in high-power fiber lasers and amplifiers. It has been proposed that TMI can be suppressed by exciting multiple modes in a highly multimode fiber. We derive a semi-analytic frequency-domain theory of the threshold for the onset of TMI in narrowband fiber amplifiers under arbitrary multimode input excitation for general fiber geometries. Our detailed model includes the effect of gain saturation, pump depletion, and mode-dependent gain. We show that TMI results from the exponential growth of noise in all the modes at downshifted frequencies due to the thermo-optical coupling. The noise growth rate in each mode is given by the sum of signal powers in various modes weighted by pairwise thermo-optical coupling coefficients. We calculate thermo-optical coupling coefficients for all ∼104 pairs of modes in a standard circular multimode fiber and show that modes with large transverse spatial frequency mismatch are weakly coupled, resulting in a banded coupling matrix. This short-range behavior is due to the diffusive nature of the heat propagation, which mediates the coupling and leads to a lower noise growth rate upon multimode excitation compared to a single mode, resulting in significant TMI suppression. We find that the TMI threshold scales linearly with the number of modes that are excited asymptotically, leading to roughly an order of magnitude increase in the TMI threshold in an 82-mode fiber amplifier.
{"title":"Theory of transverse mode instability in fiber amplifiers with multimode excitations","authors":"Kabish Wisal, Chun-Wei Chen, Hui Cao, A. Douglas Stone","doi":"10.1063/5.0206859","DOIUrl":"https://doi.org/10.1063/5.0206859","url":null,"abstract":"Transverse Mode Instability (TMI) that results from dynamic nonlinear thermo-optical scattering is the primary limitation to power scaling in high-power fiber lasers and amplifiers. It has been proposed that TMI can be suppressed by exciting multiple modes in a highly multimode fiber. We derive a semi-analytic frequency-domain theory of the threshold for the onset of TMI in narrowband fiber amplifiers under arbitrary multimode input excitation for general fiber geometries. Our detailed model includes the effect of gain saturation, pump depletion, and mode-dependent gain. We show that TMI results from the exponential growth of noise in all the modes at downshifted frequencies due to the thermo-optical coupling. The noise growth rate in each mode is given by the sum of signal powers in various modes weighted by pairwise thermo-optical coupling coefficients. We calculate thermo-optical coupling coefficients for all ∼104 pairs of modes in a standard circular multimode fiber and show that modes with large transverse spatial frequency mismatch are weakly coupled, resulting in a banded coupling matrix. This short-range behavior is due to the diffusive nature of the heat propagation, which mediates the coupling and leads to a lower noise growth rate upon multimode excitation compared to a single mode, resulting in significant TMI suppression. We find that the TMI threshold scales linearly with the number of modes that are excited asymptotically, leading to roughly an order of magnitude increase in the TMI threshold in an 82-mode fiber amplifier.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"29 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141516977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Chao Pang, Yu-hao Deng, Ezat Kheradmand, Luis Moreno Hagelsieb, Yujie Guo, David Cheyns, Pieter Geiregat, Zeger Hens, Dries Van Thourhout
Silicon photonics faces a persistent challenge in extending photodetection capabilities beyond the 1.6 µm wavelength range, primarily due to the lack of appropriate epitaxial materials. Colloidal quantum dots present a promising solution here, offering distinct advantages, such as infrared wavelength tunability, cost-effectiveness, and facile deposition. Their unique properties position them as a potential candidate for enabling photodetection in silicon photonics beyond the conventional telecom wavelength, thereby expanding the potential applications and capabilities within this domain. In this study, we have successfully integrated lead sulfide (PbS) colloidal quantum dot photodiodes (QDPDs) onto silicon waveguides using standard process techniques. The integrated photodiodes exhibit a remarkable responsivity of 1.3 A/W (with an external quantum efficiency of 74.8%) at a wavelength of 2.1 µm, a low dark current of only 106 nA, and a bandwidth of 1.1 MHz under a −3 V bias. To demonstrate the scalability of our integration approach, we have developed a compact 8-channel spectrometer incorporating an array of QDPDs. This achievement marks a significant step toward realizing a cost-effective photodetector solution for silicon photonics, particularly tailored for a wide range of sensing applications around the 2 µm wavelength range.
{"title":"A silicon photonics waveguide-coupled colloidal quantum dot photodiode sensitive beyond 1.6 µm","authors":"Chao Pang, Yu-hao Deng, Ezat Kheradmand, Luis Moreno Hagelsieb, Yujie Guo, David Cheyns, Pieter Geiregat, Zeger Hens, Dries Van Thourhout","doi":"10.1063/5.0206386","DOIUrl":"https://doi.org/10.1063/5.0206386","url":null,"abstract":"Silicon photonics faces a persistent challenge in extending photodetection capabilities beyond the 1.6 µm wavelength range, primarily due to the lack of appropriate epitaxial materials. Colloidal quantum dots present a promising solution here, offering distinct advantages, such as infrared wavelength tunability, cost-effectiveness, and facile deposition. Their unique properties position them as a potential candidate for enabling photodetection in silicon photonics beyond the conventional telecom wavelength, thereby expanding the potential applications and capabilities within this domain. In this study, we have successfully integrated lead sulfide (PbS) colloidal quantum dot photodiodes (QDPDs) onto silicon waveguides using standard process techniques. The integrated photodiodes exhibit a remarkable responsivity of 1.3 A/W (with an external quantum efficiency of 74.8%) at a wavelength of 2.1 µm, a low dark current of only 106 nA, and a bandwidth of 1.1 MHz under a −3 V bias. To demonstrate the scalability of our integration approach, we have developed a compact 8-channel spectrometer incorporating an array of QDPDs. This achievement marks a significant step toward realizing a cost-effective photodetector solution for silicon photonics, particularly tailored for a wide range of sensing applications around the 2 µm wavelength range.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"2012 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141516979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
In multicolor fluorescence microscopy, it is crucial to orient biological structures at a single-cell resolution based on precise anatomical annotations of cytoarchitecture images. However, during synchronous multicolor imaging, due to spectral mixing, the crosstalk from the blue signals of 4′,6-diamidino-2-phenylindole (DAPI)-stained cytoarchitecture images to the green waveband hinders the visualization and identification of green signals. Here, we proposed a deep learning-based framework named the crosstalk elimination and cytoarchitecture enhancement pipeline (CECEP) to simultaneously acquire crosstalk-free signals in the green channel and high-contrast DAPI-stained cytoarchitecture images during multicolor fluorescence imaging. For the CECEP network, we proposed an unsupervised learning algorithm named the cytoarchitecture enhancement network (CENet), which increased the signal-to-background ratio (SBR) of the cytoarchitecture images from 1.5 to 15.0 at a reconstruction speed of 25 Hz for 1800 × 1800 pixel images. The CECEP network is widely applicable to images of different quality, different types of tissues, and different multicolor fluorescence microscopy. In addition, the CECEP network can also facilitate various downstream analysis tasks, such as cell recognition, structure tensor calculation, and brain region segmentation. With the CECEP network, we simultaneously acquired two specific fluorescence-labeled neuronal distributions and their colocated high-SBR cytoarchitecture images without crosstalk throughout the brain. Experimental results demonstrate that our method could potentially facilitate multicolor fluorescence imaging applications in biology, such as revealing and visualizing different types of biological structures with precise locations and orientations.
{"title":"Unsupervised learning enables multicolor synchronous fluorescence microscopy without cytoarchitecture crosstalk","authors":"Bolin Lu, Zhangheng Ding, Kefu Ning, Xiaoyu Zhang, Xiangning Li, Jiangjiang Zhao, Ruiheng Xie, Dan Shen, Jiahong Hu, Tao Jiang, Jianwei Chen, Hui Gong, Jing Yuan","doi":"10.1063/5.0202622","DOIUrl":"https://doi.org/10.1063/5.0202622","url":null,"abstract":"In multicolor fluorescence microscopy, it is crucial to orient biological structures at a single-cell resolution based on precise anatomical annotations of cytoarchitecture images. However, during synchronous multicolor imaging, due to spectral mixing, the crosstalk from the blue signals of 4′,6-diamidino-2-phenylindole (DAPI)-stained cytoarchitecture images to the green waveband hinders the visualization and identification of green signals. Here, we proposed a deep learning-based framework named the crosstalk elimination and cytoarchitecture enhancement pipeline (CECEP) to simultaneously acquire crosstalk-free signals in the green channel and high-contrast DAPI-stained cytoarchitecture images during multicolor fluorescence imaging. For the CECEP network, we proposed an unsupervised learning algorithm named the cytoarchitecture enhancement network (CENet), which increased the signal-to-background ratio (SBR) of the cytoarchitecture images from 1.5 to 15.0 at a reconstruction speed of 25 Hz for 1800 × 1800 pixel images. The CECEP network is widely applicable to images of different quality, different types of tissues, and different multicolor fluorescence microscopy. In addition, the CECEP network can also facilitate various downstream analysis tasks, such as cell recognition, structure tensor calculation, and brain region segmentation. With the CECEP network, we simultaneously acquired two specific fluorescence-labeled neuronal distributions and their colocated high-SBR cytoarchitecture images without crosstalk throughout the brain. Experimental results demonstrate that our method could potentially facilitate multicolor fluorescence imaging applications in biology, such as revealing and visualizing different types of biological structures with precise locations and orientations.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"28 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141194463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
E. Di Gaetano, B. Keliehor, K. Gallacher, P. F. Griffin, M. Sorel, E. Riis, D. J. Paul
A new epitaxial layer design with a double mode expander layer, high refractive index claddings, and an aluminum-free active area has been used to demonstrate distributed feedback lasers operating at 778.1 nm wavelength with reduced Lorentzian linewidth aimed at miniature atomic clock applications. The design also reduces the vertical beam divergence to improve the modal matching with optical fibers as well as maintain the high power output and reduce the emission linewidth. The lasers demonstrate single-mode operation with an over 35 dB side-mode suppression ratio, a power output ≤58 mW, a coupling efficiency to tapered fibers ≤40%, and a Lorentzian linewidth of 3.7 kHz. The performance allowed the free-running distributed feedback lasers to demonstrate spectroscopy of Rb vapor, which resolved the 85Rb and 87Rb two-photon transitions.
{"title":"778.1 nm distributed feedback lasers for Rb two-photon atomic systems with sub-4 kHz linewidths","authors":"E. Di Gaetano, B. Keliehor, K. Gallacher, P. F. Griffin, M. Sorel, E. Riis, D. J. Paul","doi":"10.1063/5.0191088","DOIUrl":"https://doi.org/10.1063/5.0191088","url":null,"abstract":"A new epitaxial layer design with a double mode expander layer, high refractive index claddings, and an aluminum-free active area has been used to demonstrate distributed feedback lasers operating at 778.1 nm wavelength with reduced Lorentzian linewidth aimed at miniature atomic clock applications. The design also reduces the vertical beam divergence to improve the modal matching with optical fibers as well as maintain the high power output and reduce the emission linewidth. The lasers demonstrate single-mode operation with an over 35 dB side-mode suppression ratio, a power output ≤58 mW, a coupling efficiency to tapered fibers ≤40%, and a Lorentzian linewidth of 3.7 kHz. The performance allowed the free-running distributed feedback lasers to demonstrate spectroscopy of Rb vapor, which resolved the 85Rb and 87Rb two-photon transitions.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"2011 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141194098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
In this paper, we investigate the role of solar laser technology as a pivotal element in advancing sustainable and renewable energy. We begin by examining its wide-ranging applications across diverse fields, including remote communication, energy storage through magnesium production, and space exploration and communication. We address the current challenges faced by solar laser technology, which include the necessity for miniaturization, operation at natural sunlight intensity without the need for concentrated power, and efficient energy conversion. These improvements are essential to elevate their operational performance, beam quality, and cost-effectiveness. The promising prospects of space-based solar-pumped lasers and their potential role in magnesium generation for a sustainable energy future highlight some of the vast application opportunities that this novel technology could offer.
{"title":"Solar lasers: Why not?","authors":"Michael Küblböck, Jonathan Will, Hanieh Fattahi","doi":"10.1063/5.0209355","DOIUrl":"https://doi.org/10.1063/5.0209355","url":null,"abstract":"In this paper, we investigate the role of solar laser technology as a pivotal element in advancing sustainable and renewable energy. We begin by examining its wide-ranging applications across diverse fields, including remote communication, energy storage through magnesium production, and space exploration and communication. We address the current challenges faced by solar laser technology, which include the necessity for miniaturization, operation at natural sunlight intensity without the need for concentrated power, and efficient energy conversion. These improvements are essential to elevate their operational performance, beam quality, and cost-effectiveness. The promising prospects of space-based solar-pumped lasers and their potential role in magnesium generation for a sustainable energy future highlight some of the vast application opportunities that this novel technology could offer.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"28 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141166773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Qinan Jiang, Minglin Zhao, Yuanxiang Wang, Shuolin Wang, Jiantai Dou, Jun Liu, Bo Li, Youyou Hu
In this work, the second harmonic (SH) of higher-order Poincaré sphere (HOPS) beam was introduced and demonstrated with two orthogonal 5%MgO:PPLN crystals. Based on the quasi-phase-matching technique, the vectorial coupled wave equations were derived to simulate the SH of HOPS beams through the two crystals, including the cylindrical vector beams (CVBs), elliptically polarized CVBs (EPCVBs), and circularly polarized vortex beams. Then, the experimental setup was established to reveal that the SH of CVBs and EPCVBs present the four-lobed structure and still exhibit vector characteristics. Meanwhile, the circularly polarized vortex beams become the linearly polarized vortex beams with double phase topology, confirming the conservation of orbital angular momentum. Moreover, the maximum SH conversion efficiency of CVBs, EPCVBs, and circularly polarized vortex beams can reach 25.3%, 23.4%, and 29.4%, respectively, which may be instructive for promoting the SH generation of vector vortex beams with high efficiency.
{"title":"Second harmonic of higher-order Poincaré sphere beam with two orthogonal 5%MgO:PPLN crystals","authors":"Qinan Jiang, Minglin Zhao, Yuanxiang Wang, Shuolin Wang, Jiantai Dou, Jun Liu, Bo Li, Youyou Hu","doi":"10.1063/5.0198012","DOIUrl":"https://doi.org/10.1063/5.0198012","url":null,"abstract":"In this work, the second harmonic (SH) of higher-order Poincaré sphere (HOPS) beam was introduced and demonstrated with two orthogonal 5%MgO:PPLN crystals. Based on the quasi-phase-matching technique, the vectorial coupled wave equations were derived to simulate the SH of HOPS beams through the two crystals, including the cylindrical vector beams (CVBs), elliptically polarized CVBs (EPCVBs), and circularly polarized vortex beams. Then, the experimental setup was established to reveal that the SH of CVBs and EPCVBs present the four-lobed structure and still exhibit vector characteristics. Meanwhile, the circularly polarized vortex beams become the linearly polarized vortex beams with double phase topology, confirming the conservation of orbital angular momentum. Moreover, the maximum SH conversion efficiency of CVBs, EPCVBs, and circularly polarized vortex beams can reach 25.3%, 23.4%, and 29.4%, respectively, which may be instructive for promoting the SH generation of vector vortex beams with high efficiency.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"38 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141166274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Non-destructive testing (NDT) is crucial for ensuring product quality and safety across various industries. Conventional methods, such as ultrasonic, terahertz, and x-ray imaging, have limitations in terms of probe-contact requirement, depth resolution, or radiation risks. Optical coherence tomography (OCT) is a promising alternative to solve these limitations, but it suffers from strong scattering, limiting its penetration depth. Recently, OCT in the mid-infrared (MIR) spectral region has attracted attention with a significantly lower scattering rate than in the near-infrared region. However, the highest reported A-scan rate of MIR-OCT has been 3 kHz, which requires long data acquisition time to take an image, unsatisfying industrial demands for real-time diagnosis. Here, we present a high-speed MIR-OCT system operating in the 3–4 µm region that employs the frequency-swept spectrum detection in OCT technique based on time-stretch infrared spectroscopy. By integrating a broadband femtosecond MIR pulsed laser operating at a repetition rate of 50 MHz, we achieved an A-scan rate of 1 MHz with an axial resolution of 11.6 µm, a 10 dB roll-off depth of about 700 µm, and a sensitivity of 55 dB. As a proof-of-concept demonstration, we imaged the surface of substrates covered by highly scattering paint coatings. The demonstrated A-scan rate surpasses previous state of the art by more than two orders of magnitude, paving the way for real-time NDT of industrial products, cultural assets, and structures.
无损检测（NDT）对于确保各行各业的产品质量和安全至关重要。超声波、太赫兹和 X 射线成像等传统方法在探头接触要求、深度分辨率或辐射风险方面存在局限性。光学相干断层扫描（OCT）是解决这些局限性的一个很有前途的替代方法，但它的散射很强，限制了其穿透深度。最近，中红外（MIR）光谱区域的光学相干断层扫描技术引起了人们的关注，因为它的散射率明显低于近红外区域。然而，目前报道的 MIR-OCT 最高 A 扫描速率为 3 kHz，这就需要较长的数据采集时间来获取图像，无法满足实时诊断的工业需求。在此，我们提出了一种工作在 3-4 µm 区域的高速 MIR-OCT 系统，该系统在基于时间拉伸红外光谱学的 OCT 技术中采用了频扫光谱检测技术。通过集成一个以 50 MHz 重复频率工作的宽带飞秒 MIR 脉冲激光器，我们实现了 1 MHz 的 A 扫描频率，轴向分辨率为 11.6 µm，10 dB 滚降深度约为 700 µm，灵敏度为 55 dB。作为概念验证演示，我们对被高散射涂料覆盖的基底表面进行了成像。所演示的 A 扫描速率比以前的技术水平高出两个数量级以上，为工业产品、文化资产和结构的实时无损检测铺平了道路。
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