Adaptive optical microscopy via virtual-imaging-assisted wavefront sensing for high-resolution tissue imagingPhotoniX - - 2022
Zhou Zhou, Jiangfeng Huang, Xiang Li, Xiujuan Gao, Zhongyun Chen, Zhenfei Jiao, Zhihong Zhang, Luo Qinghong, Ling Fu
AbstractAdaptive optics (AO) is a powerful tool for optical microscopy to counteract the effects of optical aberrations and improve the imaging performance in biological tissues. The diversity of sample characteristics entails the use of different AO schemes to measure the underlying aberrations. Here, we present an indirect wavefront sensing method leveraging a virtual imaging scheme and a structural-similarity-based shift measurement algorithm to enable aberration measurement using intrinsic structures even with temporally varying signals. We achieved high-resolution two-photon imaging in a variety of biological samples, including fixed biological tissues and living animals, after aberration correction. We present AO-incorporated subtractive imaging to show that our method can be readily integrated with resolution enhancement techniques to obtain higher resolution in biological tissues. The robustness of our method to signal variation is demonstrated by both simulations and aberration measurement on neurons exhibiting spontaneous activity in a living larval zebrafish.
Nonlinear meta-optics towards applicationsPhotoniX - Tập 2 - Trang 1-20 - 2021
Yun Zhao, Yuanmu Yang, Hong-Bo Sun
Nonlinear optical effects have enabled numerous applications such as laser frequency conversion, ultrafast electro-optical, and all-optical modulation. Both gaseous and bulk media have conventionally been used for free-space nonlinear optical applications, yet they often require complex phase-matching techniques for efficient operation and may have limited operation bandwidth due to the material absorption. In the last decade, meta-optics made of subwavelength antennas or films have emerged as novel nonlinear optical media that may potentially overcome certain limitations of bulk crystals. Due to resonant enhancements of the pump laser field as well as the use of materials with extreme nonlinearity such as epsilon-near-zero materials, meta-optics can achieve strong nonlinear responses with a subwavelength thickness. Here, we review several nonlinear optical applications, such as electric-field-induced second-harmonic generation, entangled photon pair generation, terahertz generation, all-optical modulation, and high-harmonic generation that we envision meta-optics may have distinct advantages over their bulk counterparts. We outline the challenges still faced by nonlinear meta-optics and point out some potential directions.
Review: distributed time-domain sensors based on Brillouin scattering and FWM enhanced SBS for temperature, strain and acoustic wave detectionPhotoniX - Tập 2 - Trang 1-29 - 2021
Xiaoyi Bao, Zichao Zhou, Yuan Wang
Distributed time-domain Brillouin scattering fiber sensors have been widely used to measure the changes of the temperature and strain. The linear dependence of the temperature and strain on the Brillouin frequency shift enabled the distributed temperature and strain sensing based on mapping of the Brillouin gain spectrum. In addition, an acoustic wave can be detected by the four wave mixing (FWM) associated SBS process, in which phase matching condition is satisfied via up-down conversion of SBS process through birefringence matching before and after the conversion process. Brillouin scattering can be considered as the scattering of a pump wave from a moving grating (acoustic phonon) which induces a Doppler frequency shift in the resulting Stokes wave. The frequency shift is dependent on many factors including the velocity of sound in the scattering medium as well as the index of refraction. Such a process can be used to monitor the gain of random fiber laser based on SBS, the distributed acoustic wave reflect the distributed SBS gain for random lasing radiation, as well as the relative intensity noise inside the laser gain medium. In this review paper, the distributed time-domain sensing system based on Brillouin scattering including Brillouin optical time-domain reflectometry (BOTDR), Brillouin optical time-domain analysis (BOTDA), and FWM enhanced SBS for acoustic wave detection are introduced for their working principles and recent progress. The distributed Brillouin sensors based on specialty fibers for simultaneous temperature and strain measurement are summarized. Applications for the Brillouin scattering time-domain sensors are briefly discussed.
Metamaterial anapole plasmon học cho cảm biến chỉ số khúc xạ Dịch bởi AI PhotoniX -
Jin Yao, Jun‐Yu Ou, Vassili Savinov, Mu Ku Chen, Hsin Yu Kuo, Nikolay I. Zheludev, Din Ping Tsai
Tóm tắtChế độ anapole điện từ là một trạng thái ánh sáng không phát xạ, bắt nguồn từ sự can thiệp hủy diệt của bức xạ từ các mô men điện và mô men tẩm hình toro đang dao động. Các cộng hưởng liên quan đến anapole chất lượng cao có thể được sử dụng để tăng cường các đặc tính điện từ phi tuyến của vật liệu và trong các ứng dụng cảm biến. Trong công trình này, chúng tôi đã thực nghiệm chứng minh cảm biến metamaterial anapole plasmonic dùng để đo chỉ số khúc xạ của môi trường trong phần quang của quang phổ. Kết quả của chúng tôi cho thấy cảm biến thể hiện độ nhạy cao với chỉ số khúc xạ môi trường ở mức 330 nm/RIU và mức tiếng ồn là 8.7 × 10-5 RIU. Công trình này sẽ mở ra cơ hội cho các ứng dụng của metamaterials anapole trong sinh học cảm biến và quang phổ học.
Multiplexing near- and far-field functionalities with high-efficiency bi-channel metasurfacesPhotoniX - Tập 5 Số 1
Congqi Dai, Tong Liu, Dongyi Wang, Lei Zhou
AbstractPropagating waves and surface waves are two distinct types of light-transporting modes, the free control of which are both highly desired in integration photonics. However, previously realized devices are bulky in sizes, inefficient, and/or can only achieve one type of light-manipulation functionality with a single device. Here, we propose a generic approach to design bi-channel meta-devices, constructed by carefully selected meta-atoms possessing reflection phases of both structural-resonance and geometric origins, which can exhibit two distinct light-manipulation functionalities in near-field (NF) and far-field (FF) channels, respectively. After characterizing the scattering properties of basic meta-atoms and briefly stating the theoretical strategy, we design/fabricate three different meta-devices and experimentally characterize their bi-channel wave-control functionalities in the telecom regime. Our experiments show that the first two devices can multiplex the generations of NF and FF optical vortices with different topological charges, while the third one exhibits anomalous surface plasmon polariton focusing in the NF and hologram formation in the FF simultaneously. Our results expand the wave-control functionalities of metasurfaces to all wave-transporting channels, which may inspire many exciting applications in integration optics.
Ultrafast dissipative soliton generation in anomalous dispersion achieving high peak power beyond the limitation of cubic nonlinearityPhotoniX - Tập 4 - Trang 1-18 - 2023
Jinhwa Gene, Seung Kwan Kim, Sun Do Lim, Min Yong Jeon
The maximum peak power of ultrafast mode-locked lasers has been limited by cubic nonlinearity, which collapses the mode-locked pulses and consequently leads to noisy operation or satellite pulses. In this paper, we propose a concept to achieve mode-locked pulses with high peak power beyond the limitation of cubic nonlinearity with the help of dissipative resonance between quintic nonlinear phase shifts and anomalous group velocity dispersion. We first conducted a numerical study to investigate the existence of high peak power ultrafast dissipative solitons in a fiber cavity with anomalous group velocity dispersion (U-DSAD) and found four unique characteristics. We then built long cavity ultrafast thulium-doped fiber lasers and verified that the properties of the generated mode-locked pulses match well with the U-DSAD characteristics found in the numerical study. The best-performing laser generated a peak power of 330 kW and a maximum pulse energy of 80 nJ with a pulse duration of 249 fs at a repetition rate of 428 kHz. Such a high peak power exceeds that of any previous mode-locked pulses generated from a single-mode fiber laser without post-treatment. We anticipate that the means to overcome cubic nonlinearity presented in this paper can give insight in various optical fields dealing with nonlinearity to find solutions beyond the inherent limitations.
Realization of high aspect ratio metalenses by facile nanoimprint lithography using water-soluble stampsPhotoniX - Tập 4 - Trang 1-11 - 2023
Hojung Choi, Joohoon Kim, Wonjoong Kim, Junhwa Seong, Chanwoong Park, Minseok Choi, Nakhyun Kim, Jisung Ha, Cheng-Wei Qiu, Junsuk Rho, Heon Lee
Nanoimprint lithography (NIL) has attracted attention recently as a promising fabrication method for dielectric metalenses owing to its low cost and high throughput, however, high aspect ratio (HAR) nanostructures are required to manipulate the full 2π phase of light. Conventional NIL using a hard-polydimethylsiloxane (h-PDMS) mold inevitably incurs shear stress on the nanostructures which is inversely proportional to the surface area parallel to the direction of detachment. Therefore, HAR structures are subjected to larger shear stresses, causing structural failure. Herein, we propose a novel wet etching NIL method with no detachment process to fabricate flawless HAR metalenses. The water-soluble replica mold is fabricated with polyvinyl alcohol (PVA) which is simpler than an h-PDMS mold, and the flexibility of the PVA mold is suitable for direct printing as its high tensile modulus allows high-resolution patterning of HAR metalenses. The diffraction-limited focusing of the printed metalenses demonstrates that it operates as an ideal lens in the visible regime. This method can potentially be used for manufacturing various nanophotonic devices that require HAR nanostructures at low cost and high throughput, facilitating commercialization.
Vacuum-ultraviolet photodetectorsPhotoniX - - 2020
Lemin Jia, Wei Zheng, Feng Huang
Abstract
High-performance vacuum-ultraviolet (VUV) photodetectors are of great significance to space science, radiation monitoring, electronic industry and basic science. Due to the absolute advantages in VUV selective response and radiation resistance, ultra-wide bandgap semiconductors such as diamond, BN and AlN attract wide interest from researchers, and thus the researches on VUV photodetectors based on these emerging semiconductor materials have made considerable progress in the past 20 years. This paper takes ultra-wide bandgap semiconductor filterless VUV photodetectors with different working mechanisms as the object and gives a systematic review in the aspects of figures of merit, performance evaluation methods and research progress. These miniaturized and easily-integrated photodetectors with low power consumption are expected to achieve efficient VUV dynamic imaging and single photon detection in the future.
