Journals > > Topics > Research Articles
Research Articles|177 Article(s)
Research Articles
Surface plasmon resonance-based absorption across scales from superwavelength to subwavelength gratings
Zhisen Huang, Qian Zhang, Qiang Song, Shanwen Zhang, and Changhe Zhou
Metal micro-nano grating has received much attention due to its ability to provide high-efficiency light absorption. However, the current research scales of these metal gratings are focused on subwavelengths, and little attention has been paid to the absorption properties of metal gratings at other scales. We investigate the absorption properties of metal gratings based on surface plasmon resonance (SPR) across the scales from superwavelength to subwavelength. Under grazing incidence, we observe continuous strong absorption phenomena from superwavelength to subwavelength Al triangle-groove gratings (TGGs). Perfect absorption is realized at the subwavelength scale, whereas the maximum absorption at all other scales exceeds 74%. The electric field distribution gives the mechanism of the strong absorption phenomenon attributed to SPR on the surface of Al TGGs at different scales. In particular, subwavelength Al TGGs have perfectly symmetric absorption properties for different blaze angles, and the symmetry is gradually broken as the grating period’s scale increases. Furthermore, taking Al gratings with varying groove shapes for example, we extend the equivalence rule of grating grooves to subwavelength from near-wavelength and explain the symmetric absorption properties in Al TGGs. We unify the research of metal grating absorbers outside the subwavelength scale to a certain extent, and these findings also open new perspectives for the design of metal gratings in the future. Metal micro-nano grating has received much attention due to its ability to provide high-efficiency light absorption. However, the current research scales of these metal gratings are focused on subwavelengths, and little attention has been paid to the absorption properties of metal gratings at other scales. We investigate the absorption properties of metal gratings based on surface plasmon resonance (SPR) across the scales from superwavelength to subwavelength. Under grazing incidence, we observe continuous strong absorption phenomena from superwavelength to subwavelength Al triangle-groove gratings (TGGs). Perfect absorption is realized at the subwavelength scale, whereas the maximum absorption at all other scales exceeds 74%. The electric field distribution gives the mechanism of the strong absorption phenomenon attributed to SPR on the surface of Al TGGs at different scales. In particular, subwavelength Al TGGs have perfectly symmetric absorption properties for different blaze angles, and the symmetry is gradually broken as the grating period’s scale increases. Furthermore, taking Al gratings with varying groove shapes for example, we extend the equivalence rule of grating grooves to subwavelength from near-wavelength and explain the symmetric absorption properties in Al TGGs. We unify the research of metal grating absorbers outside the subwavelength scale to a certain extent, and these findings also open new perspectives for the design of metal gratings in the future.
Advanced Photonics Nexus
- Publication Date: Mar. 18, 2025
- Vol. 4, Issue 3, 036001 (2025)
Active manipulation of the optical spectral memory effect via scattering eigenchannels
Daixuan Wu, Jinye Du, Yuecheng Shen, Jiawei Luo... and Shian Zhang|Show fewer author(s)
The spectral memory effect in scattering media is crucial for applications that employ broadband illumination, as it dictates the available spectral range from independent scattering responses. Previous studies mainly considered a passive result with the average impact of the scattering medium, whereas it is vital to actively enhance or suppress this effect for applications concerned with large spectral range or fine resolution. We construct an analytical model by integrating the concepts of wave-based interference and photon-based propagation, which manifests a potential physical image for active manipulation by utilizing scattering eigenchannels. Our theoretical predictions indicate that the spectral memory effect is enhanced using high-transmission eigenchannels while it is suppressed using low-transmission eigenchannels. These predictions are supported by finite-difference time-domain simulations and experiments, demonstrating that the spectral memory effect’s range can be actively manipulated. Quantitatively, the experiments achieved variations in enhancement and suppression that exceeded threefold (∼3.27). We clarify the underlying principles of the spectral memory effect in scattering media and demonstrate active manipulation of multispectral scattering processes. The spectral memory effect in scattering media is crucial for applications that employ broadband illumination, as it dictates the available spectral range from independent scattering responses. Previous studies mainly considered a passive result with the average impact of the scattering medium, whereas it is vital to actively enhance or suppress this effect for applications concerned with large spectral range or fine resolution. We construct an analytical model by integrating the concepts of wave-based interference and photon-based propagation, which manifests a potential physical image for active manipulation by utilizing scattering eigenchannels. Our theoretical predictions indicate that the spectral memory effect is enhanced using high-transmission eigenchannels while it is suppressed using low-transmission eigenchannels. These predictions are supported by finite-difference time-domain simulations and experiments, demonstrating that the spectral memory effect’s range can be actively manipulated. Quantitatively, the experiments achieved variations in enhancement and suppression that exceeded threefold (∼3.27). We clarify the underlying principles of the spectral memory effect in scattering media and demonstrate active manipulation of multispectral scattering processes.
Advanced Photonics Nexus
- Publication Date: Mar. 14, 2025
- Vol. 4, Issue 2, 026013 (2025)
Ultrafast and precise distance measurement via real-time chirped pulse interferometry
Jiawen Zhi, Mingyang Xu, Yang Liu, Mengyu Wang... and Hanzhong Wu|Show fewer author(s)
Laser frequency combs, which are composed of a series of equally spaced coherent frequency components, have triggered revolutionary progress in precision spectroscopy and optical metrology. Length/distance is of fundamental importance in both science and technology. We describe a ranging scheme based on chirped pulse interferometry. In contrast to the traditional spectral interferometry, the local oscillator is strongly chirped which is able to meet the measurement pulses at arbitrary distances, and therefore, the dead zones can be removed. The distances can be precisely determined via two measurement steps based on the time-of-flight method and synthetic wavelength interferometry, respectively. To overcome the speed limitation of the optical spectrum analyzer, the spectrograms are stretched and detected by a fast photodetector and oscilloscope and consequently mapped into the time domain in real time. The experimental results indicate that the measurement uncertainty can be well within ±2 μm, compared with the reference distance meter. The Allan deviation can reach 0.4 μm at 4 ns averaging time and 25 nm at 1 μs and can achieve 2 nm at 100 μs averaging time. We also measured a spinning disk with grooves of different depths to verify the measurement speed, and the results show that the grooves with about 150 m / s line speed can be clearly captured. Our method provides a unique combination of non-dead zones, ultrafast measurement speed, high precision and accuracy, large ambiguity range, and only one single comb source. This system could offer a powerful solution for field measurements in practical applications in the future. Laser frequency combs, which are composed of a series of equally spaced coherent frequency components, have triggered revolutionary progress in precision spectroscopy and optical metrology. Length/distance is of fundamental importance in both science and technology. We describe a ranging scheme based on chirped pulse interferometry. In contrast to the traditional spectral interferometry, the local oscillator is strongly chirped which is able to meet the measurement pulses at arbitrary distances, and therefore, the dead zones can be removed. The distances can be precisely determined via two measurement steps based on the time-of-flight method and synthetic wavelength interferometry, respectively. To overcome the speed limitation of the optical spectrum analyzer, the spectrograms are stretched and detected by a fast photodetector and oscilloscope and consequently mapped into the time domain in real time. The experimental results indicate that the measurement uncertainty can be well within ±2 μm, compared with the reference distance meter. The Allan deviation can reach 0.4 μm at 4 ns averaging time and 25 nm at 1 μs and can achieve 2 nm at 100 μs averaging time. We also measured a spinning disk with grooves of different depths to verify the measurement speed, and the results show that the grooves with about 150 m / s line speed can be clearly captured. Our method provides a unique combination of non-dead zones, ultrafast measurement speed, high precision and accuracy, large ambiguity range, and only one single comb source. This system could offer a powerful solution for field measurements in practical applications in the future.
Advanced Photonics Nexus
- Publication Date: Mar. 11, 2025
- Vol. 4, Issue 2, 026012 (2025)
Compact narrow-linewidth solid-state 193-nm pulsed laser source utilizing an optical parametric amplifier and its vortex beam generation
Zhitao Zhang, Xiaobo Heng, Junwu Wang, Sheng Chen... and Hongwen Xuan|Show fewer author(s)
Deep ultraviolet coherent light, particularly at the wavelength of 193 nm, has become indispensable for semiconductor lithography. We present a compact solid-state nanosecond pulsed laser system capable of generating 193-nm coherent light at the repetition rate of 6 kHz. One part of the 1030-nm laser from the home-made Yb:YAG crystal amplifier is divided to generate 258 nm laser (1.2 W) by fourth-harmonic generation, and the rest is used to pump an optical parametric amplifier producing 1553 nm laser (700 mW). Frequency mixing of these beams in cascaded LiB3O5 crystals yields a 193-nm laser with 70-mW average power and a linewidth of less than 880 MHz. By introducing a spiral phase plate to the 1553-nm beam before frequency mixing, we generate a vortex beam carrying orbital angular momentum. This is, to our knowledge, the first demonstration of a 193-nm vortex beam generated from a solid-state laser. Such a beam could be valuable for seeding hybrid ArF excimer lasers and has potential applications in wafer processing and defect inspection. Deep ultraviolet coherent light, particularly at the wavelength of 193 nm, has become indispensable for semiconductor lithography. We present a compact solid-state nanosecond pulsed laser system capable of generating 193-nm coherent light at the repetition rate of 6 kHz. One part of the 1030-nm laser from the home-made Yb:YAG crystal amplifier is divided to generate 258 nm laser (1.2 W) by fourth-harmonic generation, and the rest is used to pump an optical parametric amplifier producing 1553 nm laser (700 mW). Frequency mixing of these beams in cascaded LiB3O5 crystals yields a 193-nm laser with 70-mW average power and a linewidth of less than 880 MHz. By introducing a spiral phase plate to the 1553-nm beam before frequency mixing, we generate a vortex beam carrying orbital angular momentum. This is, to our knowledge, the first demonstration of a 193-nm vortex beam generated from a solid-state laser. Such a beam could be valuable for seeding hybrid ArF excimer lasers and has potential applications in wafer processing and defect inspection.
Advanced Photonics Nexus
- Publication Date: Mar. 09, 2025
- Vol. 4, Issue 2, 026011 (2025)
Large-scale single-pixel imaging and sensing
Lintao Peng, Siyu Xie, Hui Lu, and Liheng Bian
Existing single-pixel imaging (SPI) and sensing techniques suffer from poor reconstruction quality and heavy computation cost, limiting their widespread application. To tackle these challenges, we propose a large-scale single-pixel imaging and sensing (SPIS) technique that enables high-quality megapixel SPI and highly efficient image-free sensing with a low sampling rate. Specifically, we first scan and sample the entire scene using small-size optimized patterns to obtain information-coupled measurements. Compared with the conventional full-sized patterns, small-sized optimized patterns achieve higher imaging fidelity and sensing accuracy with 1 order of magnitude fewer pattern parameters. Next, the coupled measurements are processed through a transformer-based encoder to extract high-dimensional features, followed by a task-specific plug-and-play decoder for imaging or image-free sensing. Considering that the regions with rich textures and edges are more difficult to reconstruct, we use an uncertainty-driven self-adaptive loss function to reinforce the network’s attention to these regions, thereby improving the imaging and sensing performance. Extensive experiments demonstrate that the reported technique achieves 24.13 dB megapixel SPI at a sampling rate of 3% within 1 s. In terms of sensing, it outperforms existing methods by 12% on image-free segmentation accuracy and achieves state-of-the-art image-free object detection accuracy with an order of magnitude less data bandwidth. Existing single-pixel imaging (SPI) and sensing techniques suffer from poor reconstruction quality and heavy computation cost, limiting their widespread application. To tackle these challenges, we propose a large-scale single-pixel imaging and sensing (SPIS) technique that enables high-quality megapixel SPI and highly efficient image-free sensing with a low sampling rate. Specifically, we first scan and sample the entire scene using small-size optimized patterns to obtain information-coupled measurements. Compared with the conventional full-sized patterns, small-sized optimized patterns achieve higher imaging fidelity and sensing accuracy with 1 order of magnitude fewer pattern parameters. Next, the coupled measurements are processed through a transformer-based encoder to extract high-dimensional features, followed by a task-specific plug-and-play decoder for imaging or image-free sensing. Considering that the regions with rich textures and edges are more difficult to reconstruct, we use an uncertainty-driven self-adaptive loss function to reinforce the network’s attention to these regions, thereby improving the imaging and sensing performance. Extensive experiments demonstrate that the reported technique achieves 24.13 dB megapixel SPI at a sampling rate of 3% within 1 s. In terms of sensing, it outperforms existing methods by 12% on image-free segmentation accuracy and achieves state-of-the-art image-free object detection accuracy with an order of magnitude less data bandwidth.
Advanced Photonics Nexus
- Publication Date: Feb. 26, 2025
- Vol. 4, Issue 2, 026010 (2025)
Compressed meta-optical encoder for image classification|Editors' Pick
Anna Wirth-Singh, Jinlin Xiang, Minho Choi, Johannes E. Fröch... and Arka Majumdar|Show fewer author(s)
Optical and hybrid convolutional neural networks (CNNs) recently have become of increasing interest to achieve low-latency, low-power image classification, and computer-vision tasks. However, implementing optical nonlinearity is challenging, and omitting the nonlinear layers in a standard CNN comes with a significant reduction in accuracy. We use knowledge distillation to compress modified AlexNet to a single linear convolutional layer and an electronic backend (two fully connected layers). We obtain comparable performance with a purely electronic CNN with five convolutional layers and three fully connected layers. We implement the convolution optically via engineering the point spread function of an inverse-designed meta-optic. Using this hybrid approach, we estimate a reduction in multiply-accumulate operations from 17M in a conventional electronic modified AlexNet to only 86 K in the hybrid compressed network enabled by the optical front end. This constitutes over 2 orders of magnitude of reduction in latency and power consumption. Furthermore, we experimentally demonstrate that the classification accuracy of the system exceeds 93% on the MNIST dataset of handwritten digits. Optical and hybrid convolutional neural networks (CNNs) recently have become of increasing interest to achieve low-latency, low-power image classification, and computer-vision tasks. However, implementing optical nonlinearity is challenging, and omitting the nonlinear layers in a standard CNN comes with a significant reduction in accuracy. We use knowledge distillation to compress modified AlexNet to a single linear convolutional layer and an electronic backend (two fully connected layers). We obtain comparable performance with a purely electronic CNN with five convolutional layers and three fully connected layers. We implement the convolution optically via engineering the point spread function of an inverse-designed meta-optic. Using this hybrid approach, we estimate a reduction in multiply-accumulate operations from 17M in a conventional electronic modified AlexNet to only 86 K in the hybrid compressed network enabled by the optical front end. This constitutes over 2 orders of magnitude of reduction in latency and power consumption. Furthermore, we experimentally demonstrate that the classification accuracy of the system exceeds 93% on the MNIST dataset of handwritten digits.
Advanced Photonics Nexus
- Publication Date: Feb. 25, 2025
- Vol. 4, Issue 2, 026009 (2025)
Microwave photonic prototype for concurrent radar detection and spectrum sensing over an 8 to 40 GHz bandwidth|Editors' Pick
Taixia Shi, Dingding Liang, Lu Wang, Lin Li... and Yang Chen|Show fewer author(s)
A microwave photonic prototype for concurrent radar detection and spectrum sensing is proposed. A direct digital synthesizer and an analog electronic circuit are integrated to generate an intermediate frequency (IF) linearly frequency-modulated (LFM) signal ranging from 2.5 to 9.5 GHz, with an instantaneous bandwidth of 1 GHz. The IF LFM signal is converted to the optical domain via an intensity modulator and filtered by a fiber Bragg grating to generate two second-order sidebands. The two sidebands beat each other to generate a frequency-and-bandwidth-quadrupled LFM signal. By changing the center frequency of the IF LFM signal, the radar function can be operated within 8 to 40 GHz. One second-order sideband works in conjunction with the stimulated Brillouin scattering gain spectrum for microwave frequency measurement, providing an instantaneous measurement bandwidth of 2 GHz and a frequency measurement range from 0 to 40 GHz. The prototype is demonstrated to be capable of achieving a range resolution of 3.75 cm, a range error of less than ±2 cm, a radial velocity error within ±1 cm / s, delivering clear imaging of multiple small targets, and maintaining a frequency measurement error of less than ±7 MHz and a frequency resolution of better than 20 MHz. A microwave photonic prototype for concurrent radar detection and spectrum sensing is proposed. A direct digital synthesizer and an analog electronic circuit are integrated to generate an intermediate frequency (IF) linearly frequency-modulated (LFM) signal ranging from 2.5 to 9.5 GHz, with an instantaneous bandwidth of 1 GHz. The IF LFM signal is converted to the optical domain via an intensity modulator and filtered by a fiber Bragg grating to generate two second-order sidebands. The two sidebands beat each other to generate a frequency-and-bandwidth-quadrupled LFM signal. By changing the center frequency of the IF LFM signal, the radar function can be operated within 8 to 40 GHz. One second-order sideband works in conjunction with the stimulated Brillouin scattering gain spectrum for microwave frequency measurement, providing an instantaneous measurement bandwidth of 2 GHz and a frequency measurement range from 0 to 40 GHz. The prototype is demonstrated to be capable of achieving a range resolution of 3.75 cm, a range error of less than ±2 cm, a radial velocity error within ±1 cm / s, delivering clear imaging of multiple small targets, and maintaining a frequency measurement error of less than ±7 MHz and a frequency resolution of better than 20 MHz.
Advanced Photonics Nexus
- Publication Date: Feb. 19, 2025
- Vol. 4, Issue 2, 026008 (2025)
Reducing variance of measurement in optical sensing based on self-Bayesian estimation
Xuezhi Zhang, Shengliang Zhang, Junfeng Jiang, Kun Liu... and Tiegen Liu|Show fewer author(s)
In traditional sensing, each parameter is treated as a real number in the signal demodulation, whereas the electric field of light is a complex number. The real and imaginary parts obey the Kramers–Kronig relationship, which is expected to help further enhance sensing precision. We propose a self-Bayesian estimate of the method, aiming at reducing measurement variance. This method utilizes the intensity and phase of the parameter to be measured, achieving statistical optimization of the estimated value through Bayesian inference, effectively reducing the measurement variance. To demonstrate the effectiveness of this method, we adopted an optical fiber heterodyne interference sensing vibration measurement system. The experimental results show that the signal-to-noise ratio is effectively improved within the frequency range of 200 to 500 kHz. Moreover, it is believed that the self-Bayesian estimation method holds broad application prospects in various types of optical sensing. In traditional sensing, each parameter is treated as a real number in the signal demodulation, whereas the electric field of light is a complex number. The real and imaginary parts obey the Kramers–Kronig relationship, which is expected to help further enhance sensing precision. We propose a self-Bayesian estimate of the method, aiming at reducing measurement variance. This method utilizes the intensity and phase of the parameter to be measured, achieving statistical optimization of the estimated value through Bayesian inference, effectively reducing the measurement variance. To demonstrate the effectiveness of this method, we adopted an optical fiber heterodyne interference sensing vibration measurement system. The experimental results show that the signal-to-noise ratio is effectively improved within the frequency range of 200 to 500 kHz. Moreover, it is believed that the self-Bayesian estimation method holds broad application prospects in various types of optical sensing.
Advanced Photonics Nexus
- Publication Date: Feb. 18, 2025
- Vol. 4, Issue 2, 026007 (2025)
Spatially resolved spin angular momentum mediated by spin–orbit interaction in tightly focused spinless vector beams in optical tweezers
Ram Nandan Kumar, Sauvik Roy, Subhasish Dutta Gupta, Nirmalya Ghosh, and Ayan Banerjee
We demonstrate an effective and optimal strategy for generating spatially resolved longitudinal spin angular momentum (LSAM) in optical tweezers by tightly focusing the first-order spirally polarized vector (SPV) beams with zero intrinsic angular momentum into a refractive index stratified medium. The stratified medium gives rise to a spherically aberrated intensity profile near the focal region of the optical tweezers, with off-axis intensity lobes in the radial direction possessing opposite LSAM (helicities corresponding to σ = + 1 and -1) compared to the beam center. We trap mesoscopic birefringent particles in an off-axis intensity lobe as well as at the beam center by modifying the trapping plane and observe particles spinning in opposite directions depending on their location. The direction of rotation depends on the particle size with larger particles spinning either clockwise or anticlockwise depending on the direction of spirality of the polarization of the SPV beam after tight focusing, while smaller particles spin in both directions depending on their spatial locations. Numerical simulations support our experimental observations. Our results introduce new avenues in spin–orbit optomechanics to facilitate novel yet straightforward avenues for exotic and complex particle manipulation in optical tweezers. We demonstrate an effective and optimal strategy for generating spatially resolved longitudinal spin angular momentum (LSAM) in optical tweezers by tightly focusing the first-order spirally polarized vector (SPV) beams with zero intrinsic angular momentum into a refractive index stratified medium. The stratified medium gives rise to a spherically aberrated intensity profile near the focal region of the optical tweezers, with off-axis intensity lobes in the radial direction possessing opposite LSAM (helicities corresponding to σ = + 1 and -1) compared to the beam center. We trap mesoscopic birefringent particles in an off-axis intensity lobe as well as at the beam center by modifying the trapping plane and observe particles spinning in opposite directions depending on their location. The direction of rotation depends on the particle size with larger particles spinning either clockwise or anticlockwise depending on the direction of spirality of the polarization of the SPV beam after tight focusing, while smaller particles spin in both directions depending on their spatial locations. Numerical simulations support our experimental observations. Our results introduce new avenues in spin–orbit optomechanics to facilitate novel yet straightforward avenues for exotic and complex particle manipulation in optical tweezers.
Advanced Photonics Nexus
- Publication Date: Feb. 18, 2025
- Vol. 4, Issue 2, 026006 (2025)
Adaptable deep learning for holographic microscopy: a case study on tissue type and system variability in label-free histopathology
Jiseong Barg, Chanseok Lee, Chunghyeong Lee, and Mooseok Jang
Holographic microscopy has emerged as a vital tool in biomedicine, enabling visualization of microscopic morphological features of tissues and cells in a label-free manner. Recently, deep learning (DL)-based image reconstruction models have demonstrated state-of-the-art performance in holographic image reconstruction. However, their utility in practice is still severely limited, as conventional training schemes could not properly handle out-of-distribution data. Here, we leverage backpropagation operation and reparameterization of the forward propagator to enable an adaptable image reconstruction model for histopathologic inspection. Only given with a training dataset of rectum tissue images captured from a single imaging configuration, our scheme consistently shows high reconstruction performance even with the input hologram of diverse tissue types at different pathological states captured under various imaging configurations. Using the proposed adaptation technique, we show that the diagnostic features of cancerous colorectal tissues, such as dirty necrosis, captured with 5× magnification and a numerical aperture (NA) of 0.1, can be reconstructed with high accuracy, whereas a given training dataset is strictly confined to normal rectum tissues acquired under the imaging configuration of 20× magnification and an NA of 0.4. Our results suggest that the DL-based image reconstruction approaches, with sophisticated adaptation techniques, could offer an extensively generalizable solution for inverse mapping problems in imaging. Holographic microscopy has emerged as a vital tool in biomedicine, enabling visualization of microscopic morphological features of tissues and cells in a label-free manner. Recently, deep learning (DL)-based image reconstruction models have demonstrated state-of-the-art performance in holographic image reconstruction. However, their utility in practice is still severely limited, as conventional training schemes could not properly handle out-of-distribution data. Here, we leverage backpropagation operation and reparameterization of the forward propagator to enable an adaptable image reconstruction model for histopathologic inspection. Only given with a training dataset of rectum tissue images captured from a single imaging configuration, our scheme consistently shows high reconstruction performance even with the input hologram of diverse tissue types at different pathological states captured under various imaging configurations. Using the proposed adaptation technique, we show that the diagnostic features of cancerous colorectal tissues, such as dirty necrosis, captured with 5× magnification and a numerical aperture (NA) of 0.1, can be reconstructed with high accuracy, whereas a given training dataset is strictly confined to normal rectum tissues acquired under the imaging configuration of 20× magnification and an NA of 0.4. Our results suggest that the DL-based image reconstruction approaches, with sophisticated adaptation techniques, could offer an extensively generalizable solution for inverse mapping problems in imaging.
Advanced Photonics Nexus
- Publication Date: Feb. 18, 2025
- Vol. 4, Issue 2, 026005 (2025)
- <
- 1
- 2
- 3
- ...
- 18
- >
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20