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Information|14 Article(s)
[in Chinese]
Junjie Ding, Chen Wang, Zhou Ju, Bowen Zhu, Bohan Sang, Bo Liu, and Jianjun Yu
We experimentally demonstrate an 80-channel wavelength division multiplexing (WDM) transmission system over a 400 km fiber link. Raman amplification results in a non-flat WDM signal spectrum. Therefore, bit allocation optimization is used to enable different channels to carry different order quadrature amplitude modulation signals according to their optical signal-noise-ratios. A neural network equalizer based on a convolutional neural network (CNN), long short-term memory (LSTM) network, and fully connected (FC) layer structure is adopted in Rx digital signal processing, in which CNN is used for characteristic extraction, LSTM is used for equalization and demodulation, and FC layers are used for output. After transmission, the bit error rate of all channels is below the 25% soft-decision forward error correction threshold, and the line rate reaches 53.76 Tbit/s. We experimentally demonstrate an 80-channel wavelength division multiplexing (WDM) transmission system over a 400 km fiber link. Raman amplification results in a non-flat WDM signal spectrum. Therefore, bit allocation optimization is used to enable different channels to carry different order quadrature amplitude modulation signals according to their optical signal-noise-ratios. A neural network equalizer based on a convolutional neural network (CNN), long short-term memory (LSTM) network, and fully connected (FC) layer structure is adopted in Rx digital signal processing, in which CNN is used for characteristic extraction, LSTM is used for equalization and demodulation, and FC layers are used for output. After transmission, the bit error rate of all channels is below the 25% soft-decision forward error correction threshold, and the line rate reaches 53.76 Tbit/s.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2023
- Vol. 60, Issue 7, 0736002 (2023)
[in Chinese]
Shuo Wang, Fangshu Li, Haocheng Lu, Wenyang Zheng, Xulin Zhao, Yang Jiang, Na Li, Ya Bai, and Peng Liu
We investigate off-axis phase-matched terahertz (THz) radiation in laser plasma pumped by few-cycle laser pulses. We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the pump pulse's focal carrier-envelope phase (CEP). Ring-like profiles of THz radiation are obtained at CEP values of 0.5 π and 1.5 π, due to the inversely symmetric local THz waveforms emitted before and after laser focus. Off-axis phase-matched THz radiation offers a tool to accurately measure the CEP of few-cycle pulses at the center of a medium. We investigate off-axis phase-matched terahertz (THz) radiation in laser plasma pumped by few-cycle laser pulses. We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the pump pulse's focal carrier-envelope phase (CEP). Ring-like profiles of THz radiation are obtained at CEP values of 0.5 π and 1.5 π, due to the inversely symmetric local THz waveforms emitted before and after laser focus. Off-axis phase-matched THz radiation offers a tool to accurately measure the CEP of few-cycle pulses at the center of a medium.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2023
- Vol. 60, Issue 7, 0736001 (2023)
[in Chinese]
Yuqing Li, Huiying Du, Yunfei Wang, Jizhou Wu, Wenliang Liu, Peng Li, Yongming Fu, Jie Ma, Liantuan Xiao, and Suotang Jia
We report the effective slowing and trapping of Cs atoms in an ultrahigh-vacuum apparatus. The heated Cs atoms in an oven are slowed using a Zeeman slower after the oven chamber and then trapped using a magneto-optical trap in a science chamber. Compared to the traditional vacuum pressure of ~10-7 Pa determined by the vapor pressure of Cs atoms in the oven chamber, the designed cold nipple and differential pumping tube are used between the oven and the oven chamber to achieve a lower vacuum pressure of ~3.6×10-9 Pa. This is beneficial for achieving and maintaining an ultrahigh vacuum in the science chamber. We demonstrate the performance of our apparatus through the effective slowing of Cs atoms and an optimal magneto-optical trap. We report the effective slowing and trapping of Cs atoms in an ultrahigh-vacuum apparatus. The heated Cs atoms in an oven are slowed using a Zeeman slower after the oven chamber and then trapped using a magneto-optical trap in a science chamber. Compared to the traditional vacuum pressure of ~10-7 Pa determined by the vapor pressure of Cs atoms in the oven chamber, the designed cold nipple and differential pumping tube are used between the oven and the oven chamber to achieve a lower vacuum pressure of ~3.6×10-9 Pa. This is beneficial for achieving and maintaining an ultrahigh vacuum in the science chamber. We demonstrate the performance of our apparatus through the effective slowing of Cs atoms and an optimal magneto-optical trap.
Laser & Optoelectronics Progress
- Publication Date: Sep. 10, 2023
- Vol. 60, Issue 17, 1736001 (2023)
[in Chinese]
Xian Liu, Zehui Zhai, Jianli Liu, and Xufei Han
The combination of an optical cavity and a proportional-integral (PI) controller is commonly used in experimental quantum optical fields. In this study, an optimal PI controller for an optical cavity was designed based on the average-squared value of the error signal. The controller was implemented using a field-programmable gate array (FPGA) data acquisition board and LabVIEW software. The overall gain of the controller is optimized by adopting the cavity transmission as an optical power reference, such that the cavity locking performance does not degrade as the optical power varies. The combination of an optical cavity and a proportional-integral (PI) controller is commonly used in experimental quantum optical fields. In this study, an optimal PI controller for an optical cavity was designed based on the average-squared value of the error signal. The controller was implemented using a field-programmable gate array (FPGA) data acquisition board and LabVIEW software. The overall gain of the controller is optimized by adopting the cavity transmission as an optical power reference, such that the cavity locking performance does not degrade as the optical power varies.
Laser & Optoelectronics Progress
- Publication Date: Aug. 10, 2023
- Vol. 60, Issue 15, 1536001 (2023)
[in Chinese]
Yue Huang, Hang Xu, Jinqiang Xu, Liwen Feng, Tianyi Wang, Lina Wang, Zhongqi Liu, Senlin Huang, and Kexin Liu
In this paper we report a compact and robust regenerative amplifier developed as the pump laser for a high repetition rate terahertz parametric amplifier. With properly chosen pump source and carefully designed cavity, Nd∶YVO4 crystal, and laser beam collimator, a maximum output pulse energy of 480 μJ has been achieved at the repetition rate of 10 kHz. The output laser has a nearly Gaussian transverse profile and a narrow bandwidth of 0.2 nm. Long-term monitoring shows an root mean square power fluctuation of about 1%. These characteristics satisfy all requirements for high repetition rate terahertz parametric amplifier. In this paper we report a compact and robust regenerative amplifier developed as the pump laser for a high repetition rate terahertz parametric amplifier. With properly chosen pump source and carefully designed cavity, Nd∶YVO4 crystal, and laser beam collimator, a maximum output pulse energy of 480 μJ has been achieved at the repetition rate of 10 kHz. The output laser has a nearly Gaussian transverse profile and a narrow bandwidth of 0.2 nm. Long-term monitoring shows an root mean square power fluctuation of about 1%. These characteristics satisfy all requirements for high repetition rate terahertz parametric amplifier.
Laser & Optoelectronics Progress
- Publication Date: Nov. 10, 2022
- Vol. 59, Issue 21, 2136001 (2022)
[in Chinese]
Shuaiyu Zhang, Guohang Hu, Lin Wang, Yongjiang Liu, Ling Wei, Yifan Zheng, and Yuchuan Shao
We design a novel wireless laser power transmission system in which the process of wireless power transmission to a dynamic target was completed based on the rotation of just one component. The design of this system not only reduces the load-bearing of the gimbal, but also avoids the degradation of beam quality caused by lens vibration when tracking dynamic targets. As a result, this WLPT system has been verified by tracking an unmanned aerial vehicle at 122 m away with an offset distance of ±26.7 mm. We believe this system offers great potential in high-power, long-distance dynamic laser power transmission.We design a novel wireless laser power transmission system in which the process of wireless power transmission to a dynamic target was completed based on the rotation of just one component. The design of this system not only reduces the load-bearing of the gimbal, but also avoids the degradation of beam quality caused by lens vibration when tracking dynamic targets. As a result, this WLPT system has been verified by tracking an unmanned aerial vehicle at 122 m away with an offset distance of ±26.7 mm. We believe this system offers great potential in high-power, long-distance dynamic laser power transmission. We design a novel wireless laser power transmission system in which the process of wireless power transmission to a dynamic target was completed based on the rotation of just one component. The design of this system not only reduces the load-bearing of the gimbal, but also avoids the degradation of beam quality caused by lens vibration when tracking dynamic targets. As a result, this WLPT system has been verified by tracking an unmanned aerial vehicle at 122 m away with an offset distance of ±26.7 mm. We believe this system offers great potential in high-power, long-distance dynamic laser power transmission.We design a novel wireless laser power transmission system in which the process of wireless power transmission to a dynamic target was completed based on the rotation of just one component. The design of this system not only reduces the load-bearing of the gimbal, but also avoids the degradation of beam quality caused by lens vibration when tracking dynamic targets. As a result, this WLPT system has been verified by tracking an unmanned aerial vehicle at 122 m away with an offset distance of ±26.7 mm. We believe this system offers great potential in high-power, long-distance dynamic laser power transmission.
Laser & Optoelectronics Progress
- Publication Date: Sep. 10, 2022
- Vol. 59, Issue 17, 1736001 (2022)
[in Chinese]
Hui Zhang, Peixuan Li, Xihua Zou, Wenlin Bai, Wei Pan, and Lianshan Yan
Exploiting microwave photonic (MWP) techniques to generate and distribute high-frequency millimeter-wave (mm-wave) signals, termed mm-wave radio over fiber (m-RoF) signals, holds considerable potential for achieving high-density and high-capacity fifth-generation and beyond networks. Herein, we experimentally validate a broadband m-RoF uplink fronthaul transmission system using the MWP downconversion concept, which comprises receiving and processing radio-frequency (RF) signals in the unlicensed V-band at around 60 GHz. The proposed system harnesses the simple cascaded modulator topology, in which an ultrawideband off-the-shelf Mach–Zehnder modulator (MZM) renders a simple-structured remote radio head by directly encoding the broadband 60 GHz uplink RF signal into the optical carrier. The nonlinear transfer function of another MZM at the center unit is explored to achieve subharmonic downconversion using cost-effective low-frequency local oscillator signals. Based on proof-of-concept experiments, mm-wave four quadrature amplitude modulation orthogonal frequency-division multiplexing signals centered at frequencies ranging from 51 GHz to 70 GHz are successfully downconverted into signals at the intermediate frequency (IF) of 1.4 GHz. In the case of 1.2 m mm-wave, free-space, and 5 km m-RoF transmissions, the obtained IF signals with a total bandwidth of 2.4 GHz achieve a bit-to-error ratio performance lower than the 7% hard-decision forward error correction limit of 3.8 × 10-3. A gross bit rate of 10 Gbit/s can be achieved over a total spectrum of up to 10 GHz, which fully covers the globally unlicensed V-band of 57-66 GHz. Exploiting microwave photonic (MWP) techniques to generate and distribute high-frequency millimeter-wave (mm-wave) signals, termed mm-wave radio over fiber (m-RoF) signals, holds considerable potential for achieving high-density and high-capacity fifth-generation and beyond networks. Herein, we experimentally validate a broadband m-RoF uplink fronthaul transmission system using the MWP downconversion concept, which comprises receiving and processing radio-frequency (RF) signals in the unlicensed V-band at around 60 GHz. The proposed system harnesses the simple cascaded modulator topology, in which an ultrawideband off-the-shelf Mach–Zehnder modulator (MZM) renders a simple-structured remote radio head by directly encoding the broadband 60 GHz uplink RF signal into the optical carrier. The nonlinear transfer function of another MZM at the center unit is explored to achieve subharmonic downconversion using cost-effective low-frequency local oscillator signals. Based on proof-of-concept experiments, mm-wave four quadrature amplitude modulation orthogonal frequency-division multiplexing signals centered at frequencies ranging from 51 GHz to 70 GHz are successfully downconverted into signals at the intermediate frequency (IF) of 1.4 GHz. In the case of 1.2 m mm-wave, free-space, and 5 km m-RoF transmissions, the obtained IF signals with a total bandwidth of 2.4 GHz achieve a bit-to-error ratio performance lower than the 7% hard-decision forward error correction limit of 3.8 × 10-3. A gross bit rate of 10 Gbit/s can be achieved over a total spectrum of up to 10 GHz, which fully covers the globally unlicensed V-band of 57-66 GHz.
Laser & Optoelectronics Progress
- Publication Date: Jul. 10, 2022
- Vol. 59, Issue 13, 1336002 (2022)
Simple and High-Efficiency Preparation Method of Biometric 3D Artificial Compound Eyes for Wide-Field Imaging
Xinxue Wu, Chaolong Fang, Zhihong Li, and Yaoju Zhang
Three-dimensional (3D) artificial compound eyes (ACEs) are helpful for wide field-of-view imaging and sensing system applications. However, existing batch preparation methods are technically challenging. A bio-inspired, simple, and high-efficiency batch preparation method is proposed, which involves bonding a sticky microlens array (MLA) polydimethylsiloxane (PDMS) film to an elastic PDMS hemisphere under pressure, followed by abrupt pressure removal. Characterizations from a scanning electron microscope and laser scanning confocal microscope show that 3D ACEs prepared using the proposed method have high numbers of uniformly distributed ommatidia with a high-quality finish. Furthermore, optical imaging investigations demonstrate that the proposed preparation method can achieve clear, distortion-free imaging with a wide field-of-view (up to 140.2°). Three-dimensional (3D) artificial compound eyes (ACEs) are helpful for wide field-of-view imaging and sensing system applications. However, existing batch preparation methods are technically challenging. A bio-inspired, simple, and high-efficiency batch preparation method is proposed, which involves bonding a sticky microlens array (MLA) polydimethylsiloxane (PDMS) film to an elastic PDMS hemisphere under pressure, followed by abrupt pressure removal. Characterizations from a scanning electron microscope and laser scanning confocal microscope show that 3D ACEs prepared using the proposed method have high numbers of uniformly distributed ommatidia with a high-quality finish. Furthermore, optical imaging investigations demonstrate that the proposed preparation method can achieve clear, distortion-free imaging with a wide field-of-view (up to 140.2°).
Laser & Optoelectronics Progress
- Publication Date: Jun. 23, 2021
- Vol. 58, Issue 12, 1236001 (2021)
Dual Channel Snapshot Computation Spectral Polarization Imaging Method
Yanli Liu, Haibo Zhao, Xiaojie Yu, Yechao Wang, Xiaoming Zhong, Fang Xue, Jing Xu, and lisha Zhang
Aiming at the problems that traditional spectral polarization imaging technology requires dynamic modulation, low luminous flux and limited spectral resolution, a new imaging method based on computational spectral imaging technology and pixel-level polarization detection is proposed. The dual-channel format is used for obtaining high-resolution spatial, spectral, and polarization target information through single imaging. Further, a dual-channel experimental device with a coded-aperture spectral polarization imaging channel and a polarization imaging channel is established to obtain spectral data cubes with four polarization states in 25 bands in the range of 450-650 nm, as well as the polarization degree and polarization angle of each band. The spectral resolution of proposed method is better than 10 nm, and the spectral reconstruction accuracy is approximately 86.3%. Furthermore, the spectral reconstruction accuracy is observed to improve by 10.5 percentage points when compared with that of the single-channel imaging method. Aiming at the problems that traditional spectral polarization imaging technology requires dynamic modulation, low luminous flux and limited spectral resolution, a new imaging method based on computational spectral imaging technology and pixel-level polarization detection is proposed. The dual-channel format is used for obtaining high-resolution spatial, spectral, and polarization target information through single imaging. Further, a dual-channel experimental device with a coded-aperture spectral polarization imaging channel and a polarization imaging channel is established to obtain spectral data cubes with four polarization states in 25 bands in the range of 450-650 nm, as well as the polarization degree and polarization angle of each band. The spectral resolution of proposed method is better than 10 nm, and the spectral reconstruction accuracy is approximately 86.3%. Furthermore, the spectral reconstruction accuracy is observed to improve by 10.5 percentage points when compared with that of the single-channel imaging method.
Laser & Optoelectronics Progress
- Publication Date: Jul. 24, 2020
- Vol. 57, Issue 14, 143601 (2020)
[in Chinese]
[in Chinese], [in Chinese], and [in Chinese]
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 2018
- Vol. 55, Issue 1, 13601 (2018)
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