In this paper, a novel approach based on frequency upconversion in ultra-thin nonlinear crystals is investigated for use in high-resolution infrared (IR) microscopy in the 5–12 µm range, an important domain for biomedical research. Traditional IR imaging encounters spatial resolution constraints due to diffraction, which are addressed via upconversion imaging using ultra-thin crystals. The present work combines a tunable IR quantum cascade laser and a short wavelength mixing laser to circumvent the classical resolution limit dictated by the Rayleigh criterion. A detailed numerical model for small signal upconversion imaging at μm-scale resolution shows good agreement with experimental data. The presented approach opens new avenues for IR applications for label-free biomedical diagnostics and spectral imaging.
{"title":"Long-wavelength, high-resolution microscopy using upconversion in ultra-thin crystals","authors":"P. Tidemand-Lichtenberg, C. Pedersen","doi":"10.1063/5.0217145","DOIUrl":"https://doi.org/10.1063/5.0217145","url":null,"abstract":"In this paper, a novel approach based on frequency upconversion in ultra-thin nonlinear crystals is investigated for use in high-resolution infrared (IR) microscopy in the 5–12 µm range, an important domain for biomedical research. Traditional IR imaging encounters spatial resolution constraints due to diffraction, which are addressed via upconversion imaging using ultra-thin crystals. The present work combines a tunable IR quantum cascade laser and a short wavelength mixing laser to circumvent the classical resolution limit dictated by the Rayleigh criterion. A detailed numerical model for small signal upconversion imaging at μm-scale resolution shows good agreement with experimental data. The presented approach opens new avenues for IR applications for label-free biomedical diagnostics and spectral imaging.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"237 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199473","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}
We present deep-ultraviolet Fourier ptychography (DUV-FP) for high-resolution chemical imaging of biological specimens in their native state without exogenous stains. This approach uses a customized 265-nm DUV LED array for angle-varied illumination, leveraging the unique DUV absorption properties of biomolecules at this wavelength region. We implemented a robust feature-domain optimization framework to overcome common challenges in Fourier ptychographic reconstruction, including vignetting, pupil aberrations, stray light problems, intensity variations, and other systematic errors. By using a 0.12 numerical aperture low-resolution objective lens, our DUV-FP prototype can resolve the 345-nm linewidth on a resolution target, demonstrating at least a four-fold resolution gain compared to the captured raw images. Testing on various biospecimens demonstrates that DUV-FP significantly enhances absorption-based chemical contrast and reveals detailed structural and molecular information. To further address the limitations of conventional FP in quantitative phase imaging, we developed a spatially coded DUV-FP system. This platform enables true quantitative phase imaging of biospecimens with DUV light, overcoming the non-uniform phase response inherent in traditional microscopy techniques. The demonstrated advancements in high-resolution, label-free chemical imaging may accelerate developments in digital pathology, potentially enabling rapid, on-site analysis of biopsy samples in clinical settings.
{"title":"Deep-ultraviolet Fourier ptychography (DUV-FP) for label-free biochemical imaging via feature-domain optimization.","authors":"Qianhao Zhao, Ruihai Wang, Shuhe Zhang, Tianbo Wang, Pengming Song, Guoan Zheng","doi":"10.1063/5.0227038","DOIUrl":"10.1063/5.0227038","url":null,"abstract":"<p><p>We present deep-ultraviolet Fourier ptychography (DUV-FP) for high-resolution chemical imaging of biological specimens in their native state without exogenous stains. This approach uses a customized 265-nm DUV LED array for angle-varied illumination, leveraging the unique DUV absorption properties of biomolecules at this wavelength region. We implemented a robust feature-domain optimization framework to overcome common challenges in Fourier ptychographic reconstruction, including vignetting, pupil aberrations, stray light problems, intensity variations, and other systematic errors. By using a 0.12 numerical aperture low-resolution objective lens, our DUV-FP prototype can resolve the 345-nm linewidth on a resolution target, demonstrating at least a four-fold resolution gain compared to the captured raw images. Testing on various biospecimens demonstrates that DUV-FP significantly enhances absorption-based chemical contrast and reveals detailed structural and molecular information. To further address the limitations of conventional FP in quantitative phase imaging, we developed a spatially coded DUV-FP system. This platform enables true quantitative phase imaging of biospecimens with DUV light, overcoming the non-uniform phase response inherent in traditional microscopy techniques. The demonstrated advancements in high-resolution, label-free chemical imaging may accelerate developments in digital pathology, potentially enabling rapid, on-site analysis of biopsy samples in clinical settings.</p>","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"9 9","pages":"090801"},"PeriodicalIF":5.4,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11409226/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142279720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
π modes are unique topological edge states appearing in Floquet systems with periodic modulations of the underlying lattice structure in the evolution variable, such as dynamically modulated Su–Schrieffer–Heeger (SSH) lattices. These edge states are anomalous states usually appearing between Floquet replicas of the same band, even if the standard topological index remains zero for this band. While linear and nonlinear π modes were observed in conservative systems, they have never been studied in the nonlinear regime in the non-Hermitian systems with structured gain and losses. Here, we show that the SSH waveguide array with periodically oscillating waveguide positions in the propagation direction and with the parity-time symmetric refractive index landscape can support π modes that are damped or amplified at different ends of the array. By including nonlinearity and nonlinear absorption into our continuous system, we achieve stable lasing in the π mode at one end of the array. The representative feature of this system is that lasing in it is thresholdless and occurs even at low gain–loss amplitudes. The degree of localization of lasing π modes can be flexibly controlled by the amplitude of transverse waveguide oscillations. This work therefore introduces a new type of topological Floquet laser and a route to manipulate π modes by structured gain and losses.
{"title":"π mode lasing in the non-Hermitian Floquet topological system","authors":"Shuang Shen, Yaroslav V. Kartashov, Yongdong Li, Meng Cao, Yiqi Zhang","doi":"10.1063/5.0217904","DOIUrl":"https://doi.org/10.1063/5.0217904","url":null,"abstract":"π modes are unique topological edge states appearing in Floquet systems with periodic modulations of the underlying lattice structure in the evolution variable, such as dynamically modulated Su–Schrieffer–Heeger (SSH) lattices. These edge states are anomalous states usually appearing between Floquet replicas of the same band, even if the standard topological index remains zero for this band. While linear and nonlinear π modes were observed in conservative systems, they have never been studied in the nonlinear regime in the non-Hermitian systems with structured gain and losses. Here, we show that the SSH waveguide array with periodically oscillating waveguide positions in the propagation direction and with the parity-time symmetric refractive index landscape can support π modes that are damped or amplified at different ends of the array. By including nonlinearity and nonlinear absorption into our continuous system, we achieve stable lasing in the π mode at one end of the array. The representative feature of this system is that lasing in it is thresholdless and occurs even at low gain–loss amplitudes. The degree of localization of lasing π modes can be flexibly controlled by the amplitude of transverse waveguide oscillations. This work therefore introduces a new type of topological Floquet laser and a route to manipulate π modes by structured gain and losses.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"4 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199474","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}
Daniel Krizan, Jiri Stipal, Jan Nedoma, Sandro Oliveira, Marcel Fajkus, Jakub Cubik, Petr Siska, Emiliano Schena, Daniela Lo Presti, Carlos Marques
Fiber optic sensors based on fiber Bragg grating (FBG) technology have the potential to revolutionize the way vital signs of the human body are measured and monitored. By leveraging their unique properties, these sensors can provide accurate and reliable data, thus enhancing the effectiveness of wearable devices. The integration of FBG sensors into different materials not only broadens their application scope but also improves user comfort and device practicality. However, some challenges remain in optimizing the embedding process to ensure sensor performance and durability. This review provides an overview of FBG technology employed for measuring vital signs of the human body reported in the past decade. The focus of the review is on the FBG embedding strategies into different materials, categorized into these three main groups (i.e., 3D printed, textiles, and polymers) and explores the implications of embedding fiber optic sensors in each category. Furthermore, it discusses the potential impact of these embedded sensors on the accuracy, comfort, and practicality of wearable devices designed for monitoring vital signs, highlighting the potential of these sensors to transform the field of health monitoring. Future research directions may include exploring new materials for embedding and refining sensor design further to improve the accuracy and comfort of these wearable devices. Ultimately, the evolution of fiber optic sensors could significantly advance the field of human vital sign monitoring, paving the way for more sophisticated and user-friendly health monitoring systems.
基于光纤布拉格光栅（FBG）技术的光纤传感器有望彻底改变测量和监测人体生命体征的方式。利用其独特的特性，这些传感器可以提供准确可靠的数据，从而提高可穿戴设备的功效。将 FBG 传感器集成到不同的材料中，不仅拓宽了其应用范围，还提高了用户舒适度和设备实用性。然而，在优化嵌入工艺以确保传感器性能和耐用性方面仍存在一些挑战。本综述概述了过去十年中用于测量人体生命体征的 FBG 技术。综述的重点是不同材料中的 FBG 嵌入策略，分为三大类（即 3D 打印、纺织品和聚合物），并探讨了在每一类材料中嵌入光纤传感器的影响。此外，报告还讨论了这些嵌入式传感器对用于监测生命体征的可穿戴设备的准确性、舒适性和实用性的潜在影响，强调了这些传感器改变健康监测领域的潜力。未来的研究方向可能包括探索新的嵌入材料和进一步完善传感器设计，以提高这些可穿戴设备的准确性和舒适性。最终，光纤传感器的发展将极大地推动人体生命体征监测领域的发展，为更先进、更方便用户的健康监测系统铺平道路。
{"title":"Embedding FBG sensors for monitoring vital signs of the human body: Recent progress over the past decade","authors":"Daniel Krizan, Jiri Stipal, Jan Nedoma, Sandro Oliveira, Marcel Fajkus, Jakub Cubik, Petr Siska, Emiliano Schena, Daniela Lo Presti, Carlos Marques","doi":"10.1063/5.0226556","DOIUrl":"https://doi.org/10.1063/5.0226556","url":null,"abstract":"Fiber optic sensors based on fiber Bragg grating (FBG) technology have the potential to revolutionize the way vital signs of the human body are measured and monitored. By leveraging their unique properties, these sensors can provide accurate and reliable data, thus enhancing the effectiveness of wearable devices. The integration of FBG sensors into different materials not only broadens their application scope but also improves user comfort and device practicality. However, some challenges remain in optimizing the embedding process to ensure sensor performance and durability. This review provides an overview of FBG technology employed for measuring vital signs of the human body reported in the past decade. The focus of the review is on the FBG embedding strategies into different materials, categorized into these three main groups (i.e., 3D printed, textiles, and polymers) and explores the implications of embedding fiber optic sensors in each category. Furthermore, it discusses the potential impact of these embedded sensors on the accuracy, comfort, and practicality of wearable devices designed for monitoring vital signs, highlighting the potential of these sensors to transform the field of health monitoring. Future research directions may include exploring new materials for embedding and refining sensor design further to improve the accuracy and comfort of these wearable devices. Ultimately, the evolution of fiber optic sensors could significantly advance the field of human vital sign monitoring, paving the way for more sophisticated and user-friendly health monitoring systems.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"10 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199475","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}
Siyuan Wang, Hongxuan Liu, Mai Wang, Hao Chen, Zhi Ma, Bingcheng Pan, Yishu Huang, Yaqi Shi, Chenlei Li, He Gao, Yeyu Tong, Zongyin Yang, Zejie Yu, Liu Liu, Daoxin Dai
Group velocity and impedance matches are prerequisites for high-speed Mach–Zehnder electro-optic (EO) modulators. However, not all platforms can realize matching conditions, restricting high-speed modulation in many practical conditions. Here, we propose and demonstrate a quasi-matching scheme to satisfy the group velocity and characteristic impedance matches by cascading fast-wave and slow-wave traveling wave electrodes. The effective group velocity can be flexibly adjusted by changing the ratio of fast-wave and slow-wave traveling wave electrodes. Moreover, the quasi-matching scheme is experimentally verified by demonstrating a 6 mm long EO modulator on a thin-film lithium-niobate-on-insulator platform with a silica cladding. The radio frequency signal insertion loss at the boundary of the slow-wave and fast-wave electrodes is less than 0.12 dB. The measured small signal EO response of the quasi-matched EO modulator drops less than 2 dB at 67 GHz, while the measured small-signal EO responses of conventional slow and fast traveling wave EO modulators drop 4 dB at 67 GHz. The measured 100 Gb/s on–off key signal eye-diagrams of the quasi-matched EO modulator also exhibit an overwhelming advantage over conventional schemes. Therefore, our results will open many opportunities for high-speed EO modulators in various platforms.
群速度和阻抗匹配是高速马赫-泽恩德光电（EO）调制器的先决条件。然而，并非所有平台都能实现匹配条件，这限制了许多实际条件下的高速调制。在此，我们提出并演示了一种准匹配方案，通过级联快波和慢波行波电极来满足群速度和特性阻抗的匹配。通过改变快波和慢波行波电极的比例，可以灵活调整有效群速度。此外，通过在带有二氧化硅包层的绝缘体铌酸锂薄膜平台上演示 6 毫米长的 EO 调制器，实验验证了准匹配方案。慢波电极和快波电极边界处的射频信号插入损耗小于 0.12 dB。准匹配 EO 调制器的测量小信号 EO 响应在 67 GHz 时下降不到 2 dB，而传统慢速和快速行波 EO 调制器的测量小信号 EO 响应在 67 GHz 时下降了 4 dB。准匹配 EO 调制器的 100 Gb/s 开关关键信号眼图测量结果也比传统方案具有压倒性优势。因此，我们的研究成果将为各种平台中的高速环氧乙烷调制器带来许多机遇。
{"title":"A quasi-matching scheme for arbitrary group velocity match in electro-optic modulation","authors":"Siyuan Wang, Hongxuan Liu, Mai Wang, Hao Chen, Zhi Ma, Bingcheng Pan, Yishu Huang, Yaqi Shi, Chenlei Li, He Gao, Yeyu Tong, Zongyin Yang, Zejie Yu, Liu Liu, Daoxin Dai","doi":"10.1063/5.0220022","DOIUrl":"https://doi.org/10.1063/5.0220022","url":null,"abstract":"Group velocity and impedance matches are prerequisites for high-speed Mach–Zehnder electro-optic (EO) modulators. However, not all platforms can realize matching conditions, restricting high-speed modulation in many practical conditions. Here, we propose and demonstrate a quasi-matching scheme to satisfy the group velocity and characteristic impedance matches by cascading fast-wave and slow-wave traveling wave electrodes. The effective group velocity can be flexibly adjusted by changing the ratio of fast-wave and slow-wave traveling wave electrodes. Moreover, the quasi-matching scheme is experimentally verified by demonstrating a 6 mm long EO modulator on a thin-film lithium-niobate-on-insulator platform with a silica cladding. The radio frequency signal insertion loss at the boundary of the slow-wave and fast-wave electrodes is less than 0.12 dB. The measured small signal EO response of the quasi-matched EO modulator drops less than 2 dB at 67 GHz, while the measured small-signal EO responses of conventional slow and fast traveling wave EO modulators drop 4 dB at 67 GHz. The measured 100 Gb/s on–off key signal eye-diagrams of the quasi-matched EO modulator also exhibit an overwhelming advantage over conventional schemes. Therefore, our results will open many opportunities for high-speed EO modulators in various platforms.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"29 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199476","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}
Dominykas Gudavičius, Lukas Kontenis, Wolfgang Langbein
We demonstrate coherent anti-Stokes Raman scattering (CARS) microscopy with 1089 foci, enabled by a high repetition rate amplified oscillator and an optical parametric amplifier. We employ a camera as a multichannel detector to acquire and separate the signals from the foci, rather than using the camera image itself. This allows us to retain the insensitivity of the imaging to scattering afforded by the non-linear excitation point-spread function, which is the hallmark of point-scanning techniques. We show frame rates of 0.3 Hz for a megapixel CARS image, limited by the camera used. The laser source and corresponding CARS signal allows for at least 1000 times higher speed, and using faster cameras would allow acquiring at that speed, opening a perspective to megapixel CARS imaging with a frame rate of more than 100 Hz.
{"title":"Thousand foci coherent anti-Stokes Raman scattering microscopy","authors":"Dominykas Gudavičius, Lukas Kontenis, Wolfgang Langbein","doi":"10.1063/5.0220474","DOIUrl":"https://doi.org/10.1063/5.0220474","url":null,"abstract":"We demonstrate coherent anti-Stokes Raman scattering (CARS) microscopy with 1089 foci, enabled by a high repetition rate amplified oscillator and an optical parametric amplifier. We employ a camera as a multichannel detector to acquire and separate the signals from the foci, rather than using the camera image itself. This allows us to retain the insensitivity of the imaging to scattering afforded by the non-linear excitation point-spread function, which is the hallmark of point-scanning techniques. We show frame rates of 0.3 Hz for a megapixel CARS image, limited by the camera used. The laser source and corresponding CARS signal allows for at least 1000 times higher speed, and using faster cameras would allow acquiring at that speed, opening a perspective to megapixel CARS imaging with a frame rate of more than 100 Hz.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"35 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199478","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}
High-performance alloy thin films and large-sized thin film wafers for infrared applications are the focus of international researchers. In this study, doped Ge1−xSnx and Ge1−yBiy semiconductor alloy films were grown on a 5-in. silicon (Si) wafer using high-quality Ge films as buffer layers. An efficient technique is presented to reduce the dark current density of near-infrared photoelectric devices. By using boron for p-type doping in Ge1−xSnx films and bismuth (Bi) for n-type doping in Ge1−yBiy films, an all-thin film planar nano-p-i-n optoelectronic device with the structure n-Ge1−yBiy/i-GeSn/p-Ge1−xSnx/Ge buffer/Si substrate has been successfully fabricated. The photoelectric performance of the device was tested, and it was found that the insertion of p-Ge1−xSnx/Ge films reduced the dark current density by 1–2 orders of magnitude. The maximum photoresponsivity reached up to 0.8 A/W, and the infrared photocurrent density ranged from 904 to 935 μA/cm2 under a +1 V bias voltage. Furthermore, the device is capable of modulating a terahertz wave using a voltage signal with a modulation bandwidth of 1.2 THz and a modulation depth of ∼83%, while the modulation rate is 0.5 MHz. This not only provides a clear demonstration of how doped alloy films and the development of nano-p-i-n heterojunctions will improve photoelectric devices’ performance in the near-infrared and terahertz bands, but it also raises the possibility of optoelectronic interconnection applications being achieved through a single device.
{"title":"All-thin film nano-optoelectronic p-GeSn/i-GeSn/n-GeBi heterojunction for near-infrared photodetection and terahertz modulation","authors":"Dainan Zhang, Youbin Zheng, Yulong Liao, Cheng Liu, Huaiwu Zhang","doi":"10.1063/5.0225536","DOIUrl":"https://doi.org/10.1063/5.0225536","url":null,"abstract":"High-performance alloy thin films and large-sized thin film wafers for infrared applications are the focus of international researchers. In this study, doped Ge1−xSnx and Ge1−yBiy semiconductor alloy films were grown on a 5-in. silicon (Si) wafer using high-quality Ge films as buffer layers. An efficient technique is presented to reduce the dark current density of near-infrared photoelectric devices. By using boron for p-type doping in Ge1−xSnx films and bismuth (Bi) for n-type doping in Ge1−yBiy films, an all-thin film planar nano-p-i-n optoelectronic device with the structure n-Ge1−yBiy/i-GeSn/p-Ge1−xSnx/Ge buffer/Si substrate has been successfully fabricated. The photoelectric performance of the device was tested, and it was found that the insertion of p-Ge1−xSnx/Ge films reduced the dark current density by 1–2 orders of magnitude. The maximum photoresponsivity reached up to 0.8 A/W, and the infrared photocurrent density ranged from 904 to 935 μA/cm2 under a +1 V bias voltage. Furthermore, the device is capable of modulating a terahertz wave using a voltage signal with a modulation bandwidth of 1.2 THz and a modulation depth of ∼83%, while the modulation rate is 0.5 MHz. This not only provides a clear demonstration of how doped alloy films and the development of nano-p-i-n heterojunctions will improve photoelectric devices’ performance in the near-infrared and terahertz bands, but it also raises the possibility of optoelectronic interconnection applications being achieved through a single device.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"45 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199479","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}
Optical refrigeration using anti-Stokes photoluminescence is now well established, especially for rare-earth-doped solids where cooling to cryogenic temperatures has recently been achieved. The cooling efficiency of optical refrigeration is constrained by the requirement that the increase in the entropy of the photon field must be greater than the decrease in the entropy of the sample. Laser radiation has been used in all demonstrated cases of optical refrigeration with the intention of minimizing the entropy of the absorbed photons. Here, we show that as long as the incident radiation is unidirectional, the loss of coherence does not significantly affect the cooling efficiency. Using a general formulation of radiation entropy as the von Neumann entropy of the photon field, we show how the cooling efficiency depends on the properties of the light source, such as wavelength, coherence, and directionality. Our results suggest that the laws of thermodynamics permit optical cooling of materials with incoherent sources, such as light emitting diodes and filtered sunlight, almost as efficiently as with lasers. Our findings have significant and immediate implications for design of compact all-solid-state devices cooled via optical refrigeration.
{"title":"Photoluminescent cooling with incoherent light","authors":"Sushrut Ghonge, Masaru Kuno, Boldizsár Jankó","doi":"10.1063/5.0217272","DOIUrl":"https://doi.org/10.1063/5.0217272","url":null,"abstract":"Optical refrigeration using anti-Stokes photoluminescence is now well established, especially for rare-earth-doped solids where cooling to cryogenic temperatures has recently been achieved. The cooling efficiency of optical refrigeration is constrained by the requirement that the increase in the entropy of the photon field must be greater than the decrease in the entropy of the sample. Laser radiation has been used in all demonstrated cases of optical refrigeration with the intention of minimizing the entropy of the absorbed photons. Here, we show that as long as the incident radiation is unidirectional, the loss of coherence does not significantly affect the cooling efficiency. Using a general formulation of radiation entropy as the von Neumann entropy of the photon field, we show how the cooling efficiency depends on the properties of the light source, such as wavelength, coherence, and directionality. Our results suggest that the laws of thermodynamics permit optical cooling of materials with incoherent sources, such as light emitting diodes and filtered sunlight, almost as efficiently as with lasers. Our findings have significant and immediate implications for design of compact all-solid-state devices cooled via optical refrigeration.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"2013 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199477","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}
Seong Cheol Lee, Soobong Park, Daewon Suk, Joonhyuk Hwang, Kiyoung Ko, Won Bae Cho, Duk-Yong Choi, Kwang-Hoon Ko, Fabian Rotermund, Hansuek Lee
The mid-infrared wavelength region is one of the most important spectral ranges for a variety of applications in monitoring and controlling molecules due to the presence of strong characteristic absorption modes of many molecules. Among various mid-infrared light sources, on-chip supercontinuum sources have garnered significant attention for their high spatial coherence, broad spectral bandwidth, compact size, and dispersion controllability. However, generating a supercontinuum that extends into the molecular fingerprint region typically requires high-energy mid-infrared pump pulses from complex optical systems. In contrast, supercontinuum generated with 1550 nm pump sources, which are generally more compact, has shown limited access to the molecular fingerprint region. In this study, we developed an on-chip supercontinuum source with a dispersive wave generated at a targeted wavelength of up to 4800 nm using a coupled pump energy of about 25 pJ. The pump pulses at a wavelength of 2340 nm were generated from a relatively compact Cr:ZnS laser oscillator. The wavelengths of the generated dispersive waves closely matched the numerically predicted wavelengths. To demonstrate the applicability of the generated dispersive waves for spectroscopic purposes, molecular absorption spectroscopy was performed on the fundamental vibrational modes of 12CO2, 13CO2, and N2O. In addition, their pressures were quantitatively estimated using cepstrum analysis on the measured absorption spectra. The uncertainty in the measured pressure was close to the theoretical limit determined by the uncertainties in the absorption line shape parameters in the HITRAN database, demonstrating the potential of this mid-infrared light source for advanced spectroscopic applications.
{"title":"On-chip mid-infrared dispersive wave generation at targeted molecular absorption wavelengths","authors":"Seong Cheol Lee, Soobong Park, Daewon Suk, Joonhyuk Hwang, Kiyoung Ko, Won Bae Cho, Duk-Yong Choi, Kwang-Hoon Ko, Fabian Rotermund, Hansuek Lee","doi":"10.1063/5.0221176","DOIUrl":"https://doi.org/10.1063/5.0221176","url":null,"abstract":"The mid-infrared wavelength region is one of the most important spectral ranges for a variety of applications in monitoring and controlling molecules due to the presence of strong characteristic absorption modes of many molecules. Among various mid-infrared light sources, on-chip supercontinuum sources have garnered significant attention for their high spatial coherence, broad spectral bandwidth, compact size, and dispersion controllability. However, generating a supercontinuum that extends into the molecular fingerprint region typically requires high-energy mid-infrared pump pulses from complex optical systems. In contrast, supercontinuum generated with 1550 nm pump sources, which are generally more compact, has shown limited access to the molecular fingerprint region. In this study, we developed an on-chip supercontinuum source with a dispersive wave generated at a targeted wavelength of up to 4800 nm using a coupled pump energy of about 25 pJ. The pump pulses at a wavelength of 2340 nm were generated from a relatively compact Cr:ZnS laser oscillator. The wavelengths of the generated dispersive waves closely matched the numerically predicted wavelengths. To demonstrate the applicability of the generated dispersive waves for spectroscopic purposes, molecular absorption spectroscopy was performed on the fundamental vibrational modes of 12CO2, 13CO2, and N2O. In addition, their pressures were quantitatively estimated using cepstrum analysis on the measured absorption spectra. The uncertainty in the measured pressure was close to the theoretical limit determined by the uncertainties in the absorption line shape parameters in the HITRAN database, demonstrating the potential of this mid-infrared light source for advanced spectroscopic applications.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"73 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199480","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}
Tingyi Zhou, Yuta Goto, Takeshi Makino, Callen MacPhee, Yiming Zhou, Asad M. Madni, Hideaki Furukawa, Naoya Wada, Bahram Jalali
Ultrafast single-shot measurement techniques with high throughput are needed for capturing rare events that occur over short time scales. Such instruments unveil non-repetitive dynamics in complex systems and enable new types of spectrometers, cameras, light scattering, and lidar systems. Photonic time stretch stands out as the most effective method for such applications. However, practical uses have been challenged by the reliance of current time stretch instruments on costly supercontinuum lasers and their fixed spectrum. The challenge is further exacerbated by such a laser’s rigid self-pulsating characteristic, which offers no ability to control the pulse timing. The latter hinders the synchronization of the optical source with the incoming signal—a crucial requirement for the detection of single-shot events. Here, we report the first demonstration of time stretch using electro-optically modulated continuous wave lasers. We do this using diode lasers and modulators commonly used in wavelength-division-multiplexing optical communication systems. This approach offers more cost-effective and compact time stretch instruments and sensors and enables the synchronization of the laser source with the incoming signal. Limitations of this new approach are also discussed, and applications in time stretch microscopy and light scattering are explored.
{"title":"Time stretch with continuous-wave lasers","authors":"Tingyi Zhou, Yuta Goto, Takeshi Makino, Callen MacPhee, Yiming Zhou, Asad M. Madni, Hideaki Furukawa, Naoya Wada, Bahram Jalali","doi":"10.1063/5.0212958","DOIUrl":"https://doi.org/10.1063/5.0212958","url":null,"abstract":"Ultrafast single-shot measurement techniques with high throughput are needed for capturing rare events that occur over short time scales. Such instruments unveil non-repetitive dynamics in complex systems and enable new types of spectrometers, cameras, light scattering, and lidar systems. Photonic time stretch stands out as the most effective method for such applications. However, practical uses have been challenged by the reliance of current time stretch instruments on costly supercontinuum lasers and their fixed spectrum. The challenge is further exacerbated by such a laser’s rigid self-pulsating characteristic, which offers no ability to control the pulse timing. The latter hinders the synchronization of the optical source with the incoming signal—a crucial requirement for the detection of single-shot events. Here, we report the first demonstration of time stretch using electro-optically modulated continuous wave lasers. We do this using diode lasers and modulators commonly used in wavelength-division-multiplexing optical communication systems. This approach offers more cost-effective and compact time stretch instruments and sensors and enables the synchronization of the laser source with the incoming signal. Limitations of this new approach are also discussed, and applications in time stretch microscopy and light scattering are explored.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"42 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199496","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}
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