journal
https://read.qxmd.com/read/38875663/cfza-camera-a-high-resolution-lensless-imaging-technique-based-on-compound-fresnel-zone-aperture
#1
JOURNAL ARTICLE
Zhanquan Tian, Lina Li, Jianshe Ma, Liangcai Cao, Ping Su
In lensless imaging using a Fresnel zone aperture (FZA), it is generally believed that the resolution is limited by the outermost ring breadth of the FZA. The limitation has the potential to be broken according to the multi-order property of binary FZAs. In this Letter, we propose to use a high-order component of the FZA as the point spread function (PSF) to develop a high-order transfer function backpropagation (HBP) algorithm to enhance the resolution. The proportion of high-order diffraction energy is low, leading to severe defocus noise in the reconstructed image...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875662/polarization-variable-line-space-grating-based-on-photoalignment-liquid-crystal
#2
JOURNAL ARTICLE
Fangfang Chen, Tong Shen, Chenwen Ma, Jingxin Sang, Chenchen Xing, Jihong Zheng, Songlin Zhuang
The application of a liquid crystal (LC) in displays has driven the development of novel LC elements. In this Letter, polarization variable line-space (PVLS) gratings based on photoalignment are fabricated, and their variable-spacing properties are derived using the vector diffraction theory. Both transmissive and reflective PVLS gratings are fabricated to validate the correctness of the derivation. Experimental results indicate that PVLS gratings have a wider wavelength response bandwidth than that of polarization volume grating (PVG)...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875661/experimental-study-of-the-influence-of-variable-external-optical-feedback-on-visible-laser-diode-speckle
#3
JOURNAL ARTICLE
Christopher Evered, Kang Li, Yuanlong Fan
This study employs an experimental setup with a variable feedback fraction (fext ), external cavity length (ECL), and pump current (J) to investigate their relationships with optical linewidth and external optical feedback-induced speckle contrast (SC) reduction in a visible laser diode. In total, speckle contrast and optical linewidth data for seven feedback fractions, two pump currents, and three external cavity lengths were collected. Achieving optical linewidths up to 3.90 nm (1/e2 width) and a reduction in speckle contrast of up to 41...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875660/tunable-nonreciprocal-metasurfaces-based-on-a-nonlinear-quasi-bound-state-in-the-continuum
#4
JOURNAL ARTICLE
Yadong Xie, Zhimin Liu, Fengqi Zhou, Xin Luo, Yumin Gong, Ziqiang Cheng, Yun You
Nonreciprocal devices are essential and crucial in optics for source protection and signal separation. A hybrid grating system consisting of a silicon grating, a graphene layer, and a silicon waveguide layer is employed to create a high-Q quasi-BIC (bound state in the continuum). Then, the high-Q properties of the quasi-BIC are harnessed to enhance the third-order nonlinear effect of silicon, thereby improving the nonreciprocal characteristics of the device. The nonreciprocal transmittance ratio of the device can be tunable by adjusting the graphene Fermi energy level, achieving tunability ranging from 0...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875659/dual-wavelength-spiral-interferometry
#5
JOURNAL ARTICLE
Yu Tokizane, Ayato Takashima, Eiji Hase, Takeshi Yasui
Spiral interferometry acquires the topography of the sample and determines the elevation or depression of the sample structure by a single measurement. The method has advantages in simple measurements and stable optical setup due to the coaxial interferometer. However, the measurable axial range was limited by the wavelength of the light. Here, we demonstrate dual-wavelength spiral interferometry without a significant modification to the original setup of the spiral interferometry. The retrieved phase profile using a synthesized wavelength of 3...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875658/full-angle-single-shot-quantitative-phase-imaging-based-on-kramers-kronig-relations
#6
JOURNAL ARTICLE
Xiang Chen, Sihong Yao, Junan Song, Tianwei Ding, Guoqing Li, Jiawei Song, Shouping Nie, Jun Ma, Caojin Yuan
As a non-interference and non-iterative method, annular-illumination quantitative phase imaging based on Kramers-Kronig relations (AIKK) can realize phase measurement with full-angle resolution enhancement under multiple exposures. In order to completely record the object spectrum with a single shot, we proposed a colorful complementary illumination method in the recording process. The angle of this illumination mode is not symmetrical with each other, so the spectrum between the three channels can complement each other to avoid spectrum loss caused by spectrum conjugation...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875657/speckle-free-coherent-imaging-through-deep-turbulence
#7
JOURNAL ARTICLE
Casey J Pellizzari, Timothy J Bate, Maya G Mandyam, Cameron J Radosevich, Samuel Horst, Mark F Spencer
We develop and validate a model-based iterative reconstruction framework for digitally correcting coherent images corrupted by deep turbulence. In general, this framework is applicable to coherent-imaging approaches that gain access to the complex-optical field; however, we demonstrate our approach with multi-shot digital holography data. To test our image correction framework, we generate calibrated deep-turbulence conditions from our laboratory testbed. Using the resulting data, we demonstrate groundbreaking performance in terms of speckle-free image correction in deep-turbulence conditions...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875656/single-drive-electro-optic-frequency-comb-source-on-a-photonic-wire-bonded-thin-film-lithium-niobate-platform
#8
JOURNAL ARTICLE
Rebecca Cheng, Xinyi Ren, Christian Reimer, Matthew Yeh, Victoria Rosborough, Juergen Musolf, Leif Johansson, Mian Zhang, Mengjie Yu, Marko Lončar
Stable pulse and flat-top frequency comb generation are an indispensable component of many photonic applications, from ranging to communications. Lithium niobate on insulator is an excellent electro-optic (EO) platform, exhibiting high modulation efficiency and low optical loss, making it a fitting candidate for pulse generation through electro-optic modulation of continuous-wave (CW) light, a commonly utilized method for generating ultrashort pulses. Here, we demonstrate an on-chip electro-optic comb generation module on thin-film lithium niobate (TFLN) consisting of a Mach-Zehnder interferometer (MZI) amplitude modulator (AM) and a cascaded phase modulator (PM) system driven by a single-electrode drive...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875655/weight-adaptive-joint-mixed-precision-quantization-and-pruning-for-neural-network-based-equalization-in-short-reach-direct-detection-links
#9
JOURNAL ARTICLE
Zhaopeng Xu, Qi Wu, Weiqi Lu, Honglin Ji, Hui Chen, Tonghui Ji, Yu Yang, Gang Qiao, Jianwei Tang, Chen Cheng, Lulu Liu, Shangcheng Wang, Junpeng Liang, Jinlong Wei, Weisheng Hu, William Shieh
Neural network (NN)-based equalizers have been widely applied for dealing with nonlinear impairments in intensity-modulated direct detection (IM/DD) systems due to their excellent performance. However, the computational complexity (CC) is a major concern that limits the real-time application of NN-based receivers. In this Letter, we propose, to our knowledge, a novel weight-adaptive joint mixed-precision quantization and pruning approach to reduce the CC of NN-based equalizers, where only integer arithmetic is taken into account instead of floating-point operations...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875654/first-order-optical-coherence-of-photonic-dimer-coherent-states
#10
JOURNAL ARTICLE
Qihang Liu, Jung-Tsung Shen
Photon-photon correlations assume a pivotal significance in optical coherence. Recently, a new, to the best of our knowledge, type of quantum photonic states, the coherent state of photonic dimers, has been introduced, wherein the fundamental building blocks are two-photon bound states, instead of individual photons as in conventional lasers. In this Letter, we investigate the first-order coherence properties of the photonic-dimer coherent states, as well as the interference patterns in a double-slit interferometer setup, and compare with the coherence properties of other optical light sources, e...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875653/compact-silicon-based-ka-band-tunable-phase-photonic-microwave-frequency-downconverter
#11
JOURNAL ARTICLE
Xingyi Jiang, Qiang Zhang, Shengyu Fang, Yan Li, Shuyue Zhang, Qikai Huang, Hui Yu
In this paper, a compact silicon-based photonic microwave frequency downconverter with broadband operation capability and continuous phase shift tunability is proposed and experimentally demonstrated. The photonic converter mainly comprises two micro-ring modulators (MRMs) connected in parallel and a cascaded resonator-based optical bandpass filter (OBPF) whose size is merely 200 × 700 µm2 . In the proposed device, a radio frequency (RF) signal and a local oscillator (LO) signal drive the two MRMs for realizing the electro-optic conversion...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875652/low-cost-and-efficient-all-group-iv-visible-shortwave-infrared-dual-band-photodetector
#12
JOURNAL ARTICLE
Guangyang Lin, Yiming Zhu, Haokun Ding, Guowei Chen, Tianwei Yang, Li Jiang, Rui Wang, Xiaowei Shentu, Cheng Li
Low-cost broadband photodetectors (PDs) based on group-IV materials are highly demanded. Herein, a vertical all group-IV graphene-i-n (Gr-i-n) structure based on sputtering-grown undoped Ge0.92 Sn0.08 /Ge multiple quantum wells (MQWs) on n-Ge substrate was proposed to realize efficient visible/shortwave infrared (VIS/SWIR) dual-band photoresponse. Harnessing Gr-germanium tin (GeSn)/Ge MQWs van der Waals heterojunctions, an extended surface depletion region was established, facilitating separation and transportation of photogenerated carriers at VIS wavelengths...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875651/tunable-giant-goos-h%C3%A3-nchen-shift-in-au-res-2-graphene-heterostructure
#13
JOURNAL ARTICLE
Yunpeng Yan, Mingjie Zha, Junxi Liu, Jiaxing Tu, Zhibo Liu
Enhancing and flexibly controlling the Goos-Hänchen (GH) shift directly is a significant challenge. Here, we report a tunable giant GH shift in a Au-ReS2 -graphene heterostructure. The GH shift of this heterostructure demonstrates strong anisotropy and a unique "sign inversion" feature as the graphene reaches a specific thickness. Flexible control and enhancement of the GH shift to the centimeter scale can be achieved by simply rotating the crystallization direction of the heterostructure. Utilizing this feature, we designed an anisotropic refractive index sensor with a high sensitivity of 1...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875650/multicolor-phase-correlation-interferometer-for-shock-wave-refractive-index-measurements
#14
JOURNAL ARTICLE
Gwendolyn T Wang, Yuzhe Peng, Wenting Sun, Yi C Mazumdar
Refractive index measurements are critical for characterizing the properties of hypersonic flows, but moderate- to high-pressure experiments require alternative methods to traditional interferometric fringe counting. In this work, we introduce a novel, to the best of our knowledge, multi-wavelength phase-correlation interferometric technique to estimate the refractive index changes across nearly discrete shock wave boundaries and also simultaneously capture optical dispersion and vibrational relaxation times...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875649/high-average-power-105%C3%A2-w-fe-znse-laser-pumped-by-radiation-of-laser-diode-side-pumped-er-yag-lasers
#15
JOURNAL ARTICLE
Yingchen Wu, Rui Zhou, Sikun Zhou, Huaijin Ren, Song Zhang, Xingbin Wei, Jianli Shang, Weimin Wang, Mingyang Leng, Wenlin Dai, Jiayu Yi, Chun Tang, Lei Chen
A high average power re-frequency operation Fe:ZnSe laser using laser diode side-pumped free-running Er:YAG lasers as activating sources is presented. Two pieces of subsurface layer doped Fe:ZnSe polycrystal are adoptive in a reflective resonator configuration and face-cooled by liquid nitrogen. A maximal Fe:ZnSe laser power of 105 W at a wavelength of 4.1 μm is achieved upon pumping by ten home-made Er:YAG lasers with fiber coupled output working at a frequency of 250 Hz and a pulse duration of ∼420 μs...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875648/dual-wavelength-distributed-feedback-laser-array-based-on-four-phase-shifted-sampled-bragg-grating-for-terahertz-generation
#16
JOURNAL ARTICLE
Yizhe Fan, Bocheng Yuan, Mohanad Al-Rubaiee, Yiming Sun, Simeng Zhu, John H Marsh, Lianping Hou
We propose and experimentally demonstrate a dual-wavelength distributed feedback (DFB) laser array utilizing a four-phase-shifted sampled Bragg grating. By using this grating, the coupling coefficient is enhanced by approximately 2.83 times compared to conventional sampled Bragg gratings. The devices exhibit a stable dual-mode lasing achieved by introducing further π-phase shifts at 1/3 and 2/3 positions along the cavity. These devices require only one stage of lithography to define both the ridge waveguide and the gratings, mitigating issues related to misalignment between them...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875647/compressive-time-stretch-spectroscopy-with-pulse-by-pulse-intensity-modulation
#17
JOURNAL ARTICLE
Akira Kawai, Ryoichi Horisaki, Takuro Ideguchi
The photonic time-stretch technique is a single-pulse broadband spectroscopy method enabled by dispersive Fourier transformation. This technique enables an extremely high spectrum acquisition rate, determined by the repetition rates of femtosecond mode-locked lasers, which are typically in the range of tens of MHz. However, achieving this high spectrum acquisition rate necessitates a compromise in either the spectral resolution or the spectral bandwidth to prevent overlaps between adjacent stretched pulses...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875646/unified-stokes-mueller-polarimetry-for-multi-photon-processes-at-varying-wavelengths
#18
JOURNAL ARTICLE
Jinxian Wu, Xiang Ma, Jiaming Liu, Chunquan Lai, Yanqiu Li
Existing polarimetry, mainly focusing on harmonic generations, overlooks the differences in retardance (DRs) caused by illuminations with different wavelengths in nonlinear processes, consequently falling short in accuracy beyond frequency doubling. In this Letter, with DRs considered, we propose a universal nonlinear Stokes-Mueller (NSM) polarimetry design involving illuminations with different wavelengths. Then, we optimize the NSM measurement model, applied to sum-frequency generation (SFG) and difference frequency generation...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875645/z-scan-of-ito-nanocrystals-grown-inside-glass
#19
JOURNAL ARTICLE
Amir Ashjari, Brian Topper, Doris Möncke
Indium tin oxide (ITO) nanocrystals 1-10 nm in size were grown via thermal treatment of a boroaluminosilicate parent glass. The nonlinear behavior of the obtained glass-ceramic was investigated with the Z-scan technique using 550 ps pulses of a 532 nm source at a 500 Hz repetition rate. The nonlinear response was rich, with the sample exhibiting third- and fifth-order nonlinearities as well as saturable absorption and two-photon absorption (TPA), depending on the locale probed. Photoinduced changes were also observed, with high intensity exposures yielding an increased magnitude of the response when lower power trials were subsequently repeated at the same sample position...
June 15, 2024: Optics Letters
https://read.qxmd.com/read/38875644/uv-enhanced-photorefractive-response-rate-in-a-thin-film-lithium-niobate-microdisk
#20
JOURNAL ARTICLE
Jiankun Hou, Boyi Xue, Ruixin Ma, Simin Yu, Yicheng Zhu, Xianfeng Chen, Juanjuan Lu, Wenjie Wan
The photorefractive (PR) effect plays a critical role in emerging photonic technologies, including dynamic volume holography and on-chip all-optical functionalities. Nevertheless, its slow response rate has posed a significant obstacle to its practical application. Here, we experimentally demonstrate the enhancement of the PR response rate in a high-Q thin-film lithium niobate (TFLN) microdisk under UV light irradiation. At an irradiation intensity of 30 mW/cm2 , the PR effect achieves a high response bandwidth of approximately 256 kHz...
June 15, 2024: Optics Letters
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