Chinese options letters 2020 issue 3 editors' pick:
Shanghua Li, Qing Wang, Rui Song, Fangfang Hou, Mingwei Gao, Chunqing Gao. Laser diode pumped high-energy single-frequency Er:YAG laser with hundreds of nanoseconds pulse duration[J]. Chinese Optics Letters, 2020, 18(3): 031401
Coherent lidar is an effective tool for remote sensing observation of atmospheric information. Coherent lidar can detect three-dimensional wind field information, and differential absorption lidar can realize remote sensing observation of gas spatial distribution. One thousand six hundred and forty-five Nm band laser has many advantages: it belongs to the human eye safety band; it is located in the atmospheric window, with high atmospheric transmittance; it is the absorption peak of methane gas, which can be used for differential absorption detection of methane gas concentration; at the same time, it belongs to the communication band, and the corresponding devices such as detectors are relatively mature, which makes this band laser widely used as the light of coherent laser detection radar Source.
The long-range coherent lidar needs a single frequency, high-energy, long pulse width (narrow linewidth) laser as the light source. The higher the single pulse energy is, the longer the detection distance is; the long pulse width of BNS not only ensures high-precision coherent measurement, but also ensures high ranging accuracy. In the current research of 1.6 μ m single frequency laser, the energy of single pulse is limited, so it is difficult to meet the requirements of long-distance and high-precision coherent laser radar. Therefore, it is very important to develop a long-range human eye safety coherent laser detection radar to develop a single frequency laser with large single pulse energy.
Dr. Li Shanghua and Dr. Wang Qing (Communication author), from Beijing University of science and technology, introduced a large energy, 100 nanosecond pulse width single frequency Er: YAG laser suitable for long-range coherent lidar in their article published in the third issue of Chinese Optics Letters 2020.
By using the scheme of double LD pumped double Er: YAG ceramic ring cavity laser, the research group realized the single frequency pulse laser output with wavelength at 1645 nm, repetition frequency at 200 Hz, maximum single pulse energy at 28.6 MJ and pulse width at the order of one hundred nanoseconds. The results show that up to now, the highest single frequency output energy in 1.6 μ M band is used, and the pulse width is still in the order of BNS.
Output characteristics of single pulse energy and pulse width of single frequency pulse laser at different repetition frequencies
The research group adopts the seed injection locking scheme, using the high stable Er: YAG single block nonplanar ring cavity laser with the output wavelength of 1645 nm as the seed, which is injected into the ring cavity laser driven amplifier to realize the single frequency pulse laser output. By comparing and analyzing the influence of different wavelength pumping on pulse energy storage and crystal thermal effect, it is determined that the wavelength of two pumps is 1.47 By increasing the cavity length of the ring resonator, the width of the high energy pulse can be kept at the level of nanosecond. The output single frequency pulse has high energy stability and beam quality. The results show that the single pulse energy and beam quality are improved significantly.
Professor Gao Chunqing, who is in charge of the research group and from Beijing University of science and technology, pointed out that this kind of Er: YAG laser with high energy and single frequency of 100 nanosecond pulse width can be used as an effective light source for long-range coherent laser radar. The scheme is simple, without traveling wave amplification, and the output is stable and reliable. The future work will focus on the application of single frequency laser in coherent lidar and differential absorption lidar. Recently, the research group has carried out the research work of coherent laser wind measurement.
Recommended reading:
1. Noise-sidebands-free and ultra-low-RIN 1.5?μm single-frequency fiber laser towards coherent optical detection
Qilai Zhao, Zhitao Zhang, Bo Wu, Tianyi Tan, Changsheng Yang, Jiulin Gan, Huihui Cheng, Zhouming Feng, Mingying Peng, Zhongmin Yang, Shanhui Xu.
Photonics Research, 2018, 6(4): 04000326
2. All fiber pulsed coherent lidar development for wind profiles measurements in boundary layers
Weifeng Diao, Xin Zhang, Jiqiao Liu, Xiaopeng Zhu, Yuan Liu, Decang Bi, Weibiao Chen.
Chinese Optics Letters, 2014, 12(7): 072801
3. 1.55 μm coherent lidar based on SPA sinusoidal frequency demodulation techniques
Dezhao Yang, Ningfang Song, Zhili Lin, Pan Ou, Yudong Jia, Mingjie Sun.
Chinese Optics Letters, 2012, 10(2): 022801
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