Letters|5 Article(s)
Spin of Micro-Propeller Structures Driven by High-Order Poincaré Beams
Qian Lin, Lei Chen, Zikuan Zhuang, Jingxuan Sun, Li Zhang, and Jianing Xie
The use of light-induced micro-motors or micro-propellers, showcasing non-contact and non-damaging characteristics, is garnering increased attention in biomedical, micro-machine, and environmental fields. The High-order Poincaré (HOP) beam, as a vector beam, provides a controllable driving force with adjustable orbital angular momentum and spin angular momentum. In this study, we present the spin of a self-assembled micro-propeller structure propelled by the HOP beam, enabling flexible control over rotation velocity and direction. Our findings reveal that modifications to the total angular momentum of the driving beam field or alterations in the micro-propeller blade structure can influence rotation velocity. This research offers an efficient and versatile approach for applications in optical micromanipulation and micromachinery. The use of light-induced micro-motors or micro-propellers, showcasing non-contact and non-damaging characteristics, is garnering increased attention in biomedical, micro-machine, and environmental fields. The High-order Poincaré (HOP) beam, as a vector beam, provides a controllable driving force with adjustable orbital angular momentum and spin angular momentum. In this study, we present the spin of a self-assembled micro-propeller structure propelled by the HOP beam, enabling flexible control over rotation velocity and direction. Our findings reveal that modifications to the total angular momentum of the driving beam field or alterations in the micro-propeller blade structure can influence rotation velocity. This research offers an efficient and versatile approach for applications in optical micromanipulation and micromachinery.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0536002 (2024)
Actively Reconfigurable Valley Topological Edge and Corner States in Photonic Crystals Based on Phase Change Material Ge2Sb2Te5
Wei Li, Yuxiang Peng, Peihao Su, Jianbo Li, Kaijun Wang, Exian Liu, Jianqiang Liu, and Mengdong He
The immunity of topological states against backscattering and structural defects provides them with a unique advantage in the exploration and design of high-precision low-loss optical devices. However, the operating bandwidth of the topological states in certain photonic structures is difficult to actively tune and flexibly reconfigure. In this study, we propose a valley topological photonic crystal (TPC) comprising two inverse honeycomb photonic crystals, consisting of hexagonal silicon and Ge2Sb2Te5 (GST) rods. When GST transitions from the amorphous phase to the crystalline phase, the edge band of the TPC appears as a significant redshift and is inversed from a"∪"to an"∩"shape with topological phase transition, which enables active tuning of the operating bandwidth and propagation direction of topological edge states. Both the topological edge and corner states in a triangular structure constructed using TPCs can be simultaneously adjusted and reconfigured via GST phase transition, along with a change in the group number of corner states. Using the adjustability of topological edge states and electromagnetic coupling between two different topological bearded interfaces, we develop a multichannel optical router with a high tuning degree of freedom, where channels can be actively reconfigured and their on/off states can be freely switched. Our study provides a strategy for the active regulation of topological states and may be beneficial for the development of reconfigurable topological optical devices. The immunity of topological states against backscattering and structural defects provides them with a unique advantage in the exploration and design of high-precision low-loss optical devices. However, the operating bandwidth of the topological states in certain photonic structures is difficult to actively tune and flexibly reconfigure. In this study, we propose a valley topological photonic crystal (TPC) comprising two inverse honeycomb photonic crystals, consisting of hexagonal silicon and Ge2Sb2Te5 (GST) rods. When GST transitions from the amorphous phase to the crystalline phase, the edge band of the TPC appears as a significant redshift and is inversed from a"∪"to an"∩"shape with topological phase transition, which enables active tuning of the operating bandwidth and propagation direction of topological edge states. Both the topological edge and corner states in a triangular structure constructed using TPCs can be simultaneously adjusted and reconfigured via GST phase transition, along with a change in the group number of corner states. Using the adjustability of topological edge states and electromagnetic coupling between two different topological bearded interfaces, we develop a multichannel optical router with a high tuning degree of freedom, where channels can be actively reconfigured and their on/off states can be freely switched. Our study provides a strategy for the active regulation of topological states and may be beneficial for the development of reconfigurable topological optical devices.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0536001 (2024)
Experimental Research on 2 kW Fiber Oscillator with 14 μm Core Diameter and Copper Welding
Shaofeng Guo, Xiaoguang Dai, Yang Peng, Xiaoxing Dai, Wenlei Zheng, Zhaohui Zhu, Tongzheng Liu, and Zhihong Xu
Laser welding is the key technology of new energy battery manufacturing. To ensure the full absorption of pump light and laser light conversion efficiency, 976 nm semiconductor laser pump technology is used, and the length of gain fiber is shortened to increase the laser stimulated Raman scattering threshold. And a novel gain fiber coiling method is provided to suppress the mode instability and improve the output beam quality. The output power of single-mode (M2≤1.1) laser is 2.25 kW, the Raman suppression ratio reaches -38 dB, and the length of energy transmission fiber (14 μm core diameter, numerical aperture is 0.07) reaches 7 m. The output laser has high brightness, small spot diameter, and high power density, which can effectively reduce the thermal effect during welding and avoids weld defects and spatters. Laser welding is the key technology of new energy battery manufacturing. To ensure the full absorption of pump light and laser light conversion efficiency, 976 nm semiconductor laser pump technology is used, and the length of gain fiber is shortened to increase the laser stimulated Raman scattering threshold. And a novel gain fiber coiling method is provided to suppress the mode instability and improve the output beam quality. The output power of single-mode (M2≤1.1) laser is 2.25 kW, the Raman suppression ratio reaches -38 dB, and the length of energy transmission fiber (14 μm core diameter, numerical aperture is 0.07) reaches 7 m. The output laser has high brightness, small spot diameter, and high power density, which can effectively reduce the thermal effect during welding and avoids weld defects and spatters.
Laser & Optoelectronics Progress
- Publication Date: Nov. 10, 2022
- Vol. 59, Issue 21, 2136002 (2022)
[in Chinese]
Jiawei Shen, Na Sun, Fangjian Xing, Zixian Guo, and Junpeng Shi
The details of cross-sectional images based on Fourier domain optical coherence tomography play an important role that is limited to nonuniform sampling, spectral dispersion, inverse discrete Fourier transform (IDFT), and noise. In this section, we propose a method for emphasizing axial details to the greatest extent possible. After removing spectral dispersion, uniform discretization in the wavenumber domain is performed based on two interferograms via a specified offset in depth, with no spectrum calibration. The sampling number in IDFT is optimized to improve axial sensitivity up to 1.62 dB. The proposed process has the advantage of being based on numerical computation rather than hardware calibration, which benefits cost, accuracy, and efficiency. The details of cross-sectional images based on Fourier domain optical coherence tomography play an important role that is limited to nonuniform sampling, spectral dispersion, inverse discrete Fourier transform (IDFT), and noise. In this section, we propose a method for emphasizing axial details to the greatest extent possible. After removing spectral dispersion, uniform discretization in the wavenumber domain is performed based on two interferograms via a specified offset in depth, with no spectrum calibration. The sampling number in IDFT is optimized to improve axial sensitivity up to 1.62 dB. The proposed process has the advantage of being based on numerical computation rather than hardware calibration, which benefits cost, accuracy, and efficiency.
Laser & Optoelectronics Progress
- Publication Date: Sep. 25, 2022
- Vol. 59, Issue 18, 1836001 (2022)
Study on Dynamic Measurement of Femtosecond Filaments Based on Time-Stretch Technology
Xiaoyue Wang, Zijian Wang, Bo Peng, Kun Huang, Ming Yan, Weiwei Liu, and Heping Zeng
In this paper, the time-stretch dispersive Fourier transform is applied to imaging femtosecond laser induced filaments. One-dimensional imaging of the transient evolution of a filament is realized by using spectral-spatial coding method combined with a fast photo-detector and an oscilloscope. The spatial resolution is 60 μm and the refresh rate reaches 54.54 MHz. The proposed method avoids the limitation of refresh rate caused by CCD and provides a new method for studying the dynamics of the filament-matter interaction. In this paper, the time-stretch dispersive Fourier transform is applied to imaging femtosecond laser induced filaments. One-dimensional imaging of the transient evolution of a filament is realized by using spectral-spatial coding method combined with a fast photo-detector and an oscilloscope. The spatial resolution is 60 μm and the refresh rate reaches 54.54 MHz. The proposed method avoids the limitation of refresh rate caused by CCD and provides a new method for studying the dynamics of the filament-matter interaction.
Laser & Optoelectronics Progress
- Publication Date: Jul. 10, 2022
- Vol. 59, Issue 13, 1336001 (2022)
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