Photonics

Research

8 pages, 3592 KiB

Open AccessCommunication

Study of Optical Rogue Waves in Two-Dimensional Disordered Lattices

by Jie Song, Meng Li, Fuqiang Li, Ying Wang, Ziyang Chen and Cibo Lou

Photonics 2024, 11(4), 373; https://doi.org/10.3390/photonics11040373 - 16 Apr 2024

Viewed by 371

We probed the impact of both the degree of disorder and nonlinearity on rogue waves (RWs) in two-dimensional disordered lattices. Our results unveiled that an increase in the disorder level under linear conditions heightened the probability of RW occurrence and simultaneously contracted the [...] Read more.

We probed the impact of both the degree of disorder and nonlinearity on rogue waves (RWs) in two-dimensional disordered lattices. Our results unveiled that an increase in the disorder level under linear conditions heightened the probability of RW occurrence and simultaneously contracted the “long tail”. Interestingly, with the introduction of nonlinearity, this “long tail” became shorter compared with linear conditions. Nevertheless, in the context of disordered media, RW occurrence probability demonstrated relative stability—a distinct deviation from its conduct within homogeneous media. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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17 pages, 1592 KiB

Open AccessArticle

Pseudo-Stilbene- and Azobenzene-Type Systems for Optical Frequency Conversion: Estimating the First-Order Molecular Hyperpolarizability

by Raiane S. Araújo, José J. Rodrigues, Jr., Márcio A. R. C. Alencar, Jamal Rafique, Sumbal Saba and Luis M. G. Abegão

Photonics 2024, 11(3), 283; https://doi.org/10.3390/photonics11030283 - 21 Mar 2024

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Abstract

This study investigates the potential of a set of pseudo-stilbene and azobenzene molecular structures to become optical frequency converters for optical communications based on a detailed exploration of the first-order molecular hyperpolarizability (

β_{H R S}

), which is the microscopic counterpart [...] Read more.

This study investigates the potential of a set of pseudo-stilbene and azobenzene molecular structures to become optical frequency converters for optical communications based on a detailed exploration of the first-order molecular hyperpolarizability (

β_{H R S}

), which is the microscopic counterpart of second harmonic generation (SHG).

β_{H R S}

values were obtained via quantum chemical calculations using the Gaussian 16 software package in solvent and gas-phase media at different wavelengths, i.e., 1064 nm, 1310 nm, and 1510 nm. The latter two wavelengths are of particular interest for optical communications. Our study focused on discerning how the molecular structure influences the

β_{H R S}

response, explicitly highlighting the influence of the azomethine group (CH=N). The results revealed that the molecular planarity, affected by this group, plays a crucial role in modulating the optical properties. The highest

β_{H R S}

value in a solvent medium using the CAM-B3LYP/6-311+G(2d,p) level of theory achieved in this work was around

1400 \times 10^{- 30} {cm}^{4} {startvolt}^{- 1}

, four orders of magnitude higher than KDP (0.2

\times 10^{- 30} {cm}^{4} {startvolt}^{- 1}

), which is a reference in SHG experiments at 1064 nm. The highest calculated

β_{H R S}

value at the same level of theory and solvent at 1310 nm and 1550 nm was

631 \times 10^{- 30} {cm}^{4} {startvolt}^{- 1}

and

4 56 \times 10^{- 30} {cm}^{4} {startvolt}^{- 1}

, respectively. All these values belong to molecular structures with azo-coupling with donor (4-NMe₂) and acceptor (4′-NO₂) peripheral groups, designated as AB-3. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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14 pages, 5689 KiB

Open AccessArticle

Enhanced Measurement of Vortex Beam Rotation Using Polarization-Assisted Particle Swarm Optimization for Phase Retrieval

by Hongyang Wang, Zijing Zhang, Qingfeng Wang, Rui Feng and Yuan Zhao

Photonics 2023, 10(12), 1293; https://doi.org/10.3390/photonics10121293 - 23 Nov 2023

Cited by 1 | Viewed by 777

Abstract

In detecting the rotation velocity of an object employing the rotational Doppler effect of vortex beams, atmospheric turbulence can easily cause phase distortion and spiral spectrum dispersion, consequently reducing velocity measurement accuracy. This study combines adaptive optical intelligence algorithms with polarization compensation information [...] Read more.

In detecting the rotation velocity of an object employing the rotational Doppler effect of vortex beams, atmospheric turbulence can easily cause phase distortion and spiral spectrum dispersion, consequently reducing velocity measurement accuracy. This study combines adaptive optical intelligence algorithms with polarization compensation information to propose a novel approach, the Stokes–Particle swarm optimization Gerchberg–Saxton (Stokes-PSO GS) algorithm, which integrates Stokes polarization information assistance and PSO for GS phase retrieval. The algorithm adjusts the phase and amplitude of the pre-compensated phase screen of the GS algorithm utilizing Stokes information of polarized vortex beam (with l_L = 5 and l_R = −5) before and after distortion. The PSO is then employed to optimize the pre-compensated phase screen and perform compensations. Simulation results at z_S-T = 200 m and

C_{n}^{2}

= 1 × 10⁻¹⁴ m^−2/3, demonstrate that the Stokes-PSO GS algorithm exhibits strong stability (small angular spectrum purity deviation, σ_{p, Stokes-PSO GS} = 0.005675% < σ_{p, GS} = 11.62%), superior optical field recovery (well-recovered Stokes optical field, up to 33.76% improvement in angular spectrum purity), and high-velocity measurement accuracy (25.93% improvement) compared to the GS algorithm. This approach enables precise measurement of the rotation velocity of the vortex beam, demonstrating its potential in practical applications. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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15 pages, 3271 KiB

Open AccessEditor’s ChoiceArticle

Fourier Single-Pixel Imaging Based on Online Modulation Pattern Binarization

by Xinding Jiang, Ziyi Tong, Zhongyang Yu, Pengfei Jiang, Lu Xu, Long Wu, Mingsheng Chen, Yong Zhang, Jianlong Zhang and Xu Yang

Photonics 2023, 10(9), 963; https://doi.org/10.3390/photonics10090963 - 23 Aug 2023

Cited by 2 | Viewed by 855

Abstract

Down-sampling Fourier single-pixel imaging is typically achieved by truncating the Fourier spectrum, where exclusively the low-frequency Fourier coefficients are extracted while discarding the high-frequency components. However, the truncation of the Fourier spectrum can lead to an undesired ringing effect in the reconstructed result. [...] Read more.

Down-sampling Fourier single-pixel imaging is typically achieved by truncating the Fourier spectrum, where exclusively the low-frequency Fourier coefficients are extracted while discarding the high-frequency components. However, the truncation of the Fourier spectrum can lead to an undesired ringing effect in the reconstructed result. Moreover, the original Fourier single-pixel imaging necessitated grayscale Fourier basis patterns for illumination. This requirement limits imaging speed because digital micromirror devices (DMDs) generate grayscale patterns at a lower refresh rate. In order to solve the above problem, a fast and high-quality Fourier single-pixel imaging reconstruction method is proposed in the paper. In the method, the threshold binarization of the Fourier base pattern is performed online to improve the DMD refresh rate, and the reconstruction quality of Fourier single-pixel imaging at a low-sampling rate is improved by generating an adversarial network. This method enables fast reconstruction of target images with higher quality despite low-sampling rates. Compared with conventional Fourier single-pixel imaging, numerical simulation and experimentation demonstrate the effectiveness of the proposed method. Notably, this method is particularly significant for fast Fourier single-pixel imaging applications. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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9 pages, 2654 KiB

Open AccessCommunication

Energy Backflow in Tightly Focused Fractional Order Vector Vortex Beams with Binary Topological Charges

by Yan Wu, Xiaobo Hu, Yuhua Li and Ruipin Chen

Photonics 2023, 10(7), 820; https://doi.org/10.3390/photonics10070820 - 14 Jul 2023

Viewed by 671

Abstract

Using the Richards–Wolf diffraction integral, the longitudinal energy evolution on the focal plane of the fractional order vector vortex (FOVV) beams was studied. These beams possessed a vortex topological charge n and a polarization topological charge m, and were subjected to tight [...] Read more.

Using the Richards–Wolf diffraction integral, the longitudinal energy evolution on the focal plane of the fractional order vector vortex (FOVV) beams was studied. These beams possessed a vortex topological charge n and a polarization topological charge m, and were subjected to tight focusing through a larger numerical aperture. Our investigation revealed the existence of backflow energy when the binary topological charges n and m satisfied the conditions of n + m = 2 or n − m = −2. The component circularly polarized vortex beams of

e^{- i 2 ϕ} {\hat{e}}_{+}

(i.e., the minus second-order vortex right circularly polarized beam) and

e^{i 2 ϕ} {\hat{e}}_{-}

(i.e., the second-order vortex left circularly polarized beam) played significant roles in the generation of reverse energy flux at the focal region. For FOVV beams with binary topological charges n and m, whose sum and difference were integers, the longitudinal energy on the focal plane exhibited axial symmetry. If the sum or the difference of the topological charges n and m was not an integer, the axisymmetric longitudinal energy on the focal plane was disrupted. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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11 pages, 2815 KiB

Open AccessCommunication

Phase Imaging through Scattering Media Using Incoherent Light Source

by Huichuan Lin, Cheng Huang, Zhimin He, Jun Zeng, Fuchang Chen, Chaoqun Yu, Yan Li, Yongtao Zhang, Huanting Chen and Jixiong Pu

Photonics 2023, 10(7), 792; https://doi.org/10.3390/photonics10070792 - 09 Jul 2023

Cited by 1 | Viewed by 1339

Abstract

Phase imaging normally employs coherent a light source while an incoherent light source is not preferred due to its random wavefront. Another challenge for practical phase imaging is imaging through scattering media, which scatter the photons in a random manner and lead to [...] Read more.

Phase imaging normally employs coherent a light source while an incoherent light source is not preferred due to its random wavefront. Another challenge for practical phase imaging is imaging through scattering media, which scatter the photons in a random manner and lead to seriously distorted images of speckles. Based on the convolutional neural network (CNN), this paper presents an approach for phase imaging through scattering media using an incoherent light source. A CNN was trained and utilized to reconstruct the target images from the captured images of speckles. Similarities of over 90% between the reconstructed images and their target images have been achieved. It was concluded that an incoherent light source can be used as an illumination source for scattering phase imaging with the assistance of deep learning technology. This phase imaging approach with an incoherent light source through scattering media can be used to record the refractive indices of transparent samples, which might lead to its application in biomedical imaging. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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14 pages, 3210 KiB

Open AccessArticle

TSDSR: Temporal–Spatial Domain Denoise Super-Resolution Photon-Efficient 3D Reconstruction by Deep Learning

by Ziyi Tong, Xinding Jiang, Jiemin Hu, Lu Xu, Long Wu, Xu Yang and Bo Zou

Photonics 2023, 10(7), 744; https://doi.org/10.3390/photonics10070744 - 28 Jun 2023

Viewed by 853

Abstract

The combination of a single-photon avalanche diode detector with a high-sensitivity and photon-efficient reconstruction algorithm can realize the reconstruction of target range image from weak light signal conditions. The limited spatial resolution of the detector and the substantial background noise remain significant challenges [...] Read more.

The combination of a single-photon avalanche diode detector with a high-sensitivity and photon-efficient reconstruction algorithm can realize the reconstruction of target range image from weak light signal conditions. The limited spatial resolution of the detector and the substantial background noise remain significant challenges in the actual detection process, hindering the accuracy of 3D reconstruction techniques. To address this challenge, this paper proposes a denoising super-resolution reconstruction network based on generative adversarial network (GAN) design. Soft thresholding is incorporated into the deep architecture as a nonlinear transformation layer to effectively filter out noise. Moreover, the Unet-based discriminator is introduced to complete the high-precision detail reconstruction. The experimental results show that the proposed network can achieve high-quality super-resolution range imaging. This approach has the potential to enhance the accuracy and quality of long-range imaging in weak light signal conditions, with broad applications in fields such as robotics, autonomous vehicles, and biomedical imaging. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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11 pages, 3521 KiB

Open AccessCommunication

Recognition of Orbital Angular Momentum of Vortex Beams Based on Convolutional Neural Network and Multi-Objective Classifier

by Yanzhu Zhang, He Zhao, Hao Wu, Ziyang Chen and Jixiong Pu

Photonics 2023, 10(6), 631; https://doi.org/10.3390/photonics10060631 - 31 May 2023

Cited by 5 | Viewed by 1220

Abstract

Vortex beams carry orbital angular momentum (OAM), and their inherent infinite dimensional eigenstates can enhance the ability for optical communication and information processing in the classical and quantum fields. The measurement of the OAM of vortex beams is of great significance for optical [...] Read more.

Vortex beams carry orbital angular momentum (OAM), and their inherent infinite dimensional eigenstates can enhance the ability for optical communication and information processing in the classical and quantum fields. The measurement of the OAM of vortex beams is of great significance for optical communication applications based on vortex beams. Most of the existing measurement methods require the beam to have a regular spiral wavefront. Nevertheless, the wavefront of the light will be distorted when a vortex beam propagates through a random medium, hindering the accurate recognition of OAM by traditional methods. Deep learning offers a solution to identify the OAM of the vortex beam from a speckle field. However, the method based on deep learning usually requires a lot of data, while it is difficult to attain a large amount of data in some practical applications. To solve this problem, we design a framework based on convolutional neural network (CNN) and multi-objective classifier (MOC), by which the OAM of vortex beams can be identified with high accuracy using a small amount of data. We find that by combining CNN with different structures and MOC, the highest accuracy reaches 96.4%, validating the feasibility of the proposed scheme. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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12 pages, 2019 KiB

Open AccessArticle

Photonic Signal Processing in Phase-Coded Lidar System

by Shuyu Chen, Long Wu, Lu Xu, Yong Zhang and Jianlong Zhang

Photonics 2023, 10(5), 598; https://doi.org/10.3390/photonics10050598 - 21 May 2023

Viewed by 1346

Abstract

The next generation of lidar systems needs to adapt to variable environments with broadened bandwidth for increased resolution. Due to their digital components, conventional lidar systems, especially imaging lidar systems, suffer from limited detector bandwidth and sampling frequency. However, photonics devices can provide [...] Read more.

The next generation of lidar systems needs to adapt to variable environments with broadened bandwidth for increased resolution. Due to their digital components, conventional lidar systems, especially imaging lidar systems, suffer from limited detector bandwidth and sampling frequency. However, photonics devices can provide a reliable technical solution with high precision and ultra-broad bandwidth. This paper presents a photonic signal processing structure for a phase-coded lidar system. Two acousto-optic modulators (AOMs) are adopted in the proposed architecture. One is used for phase-coded laser signal modulation, and the other is used for demodulation. The echo laser signal is directed to the AOM performing demodulation before the sampling of the detector, accomplishing the multiplication of the echo laser signal and the electric reference signal. The detector is controlled to accumulate the demodulated laser signal. The AOM and detector transfer the correlation calculation from electrical signals processing to photonic signals processing. This photonics-based structure greatly decreases the sampling frequency of the detector without extending the width of the laser pulses, which achieves high resolution with low sampling speed. Photonic signal processing has the promising potential of simultaneously processing signals of multiple pixels. It is going to be an effective solution for imaging lidar systems to increase resolution with available low-cost devices. Full article

(This article belongs to the Special Issue Nonlinear Optics and Hyperspectral Polarization Imaging)

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