New band atmospheric transmission characteristics based on
2.07 μm actively mode-locked fiber laser
Actively mode-locked fiber laser has been widely used due to the characteristics of narrow line-width, wavelength tunable, high repetition rate and good temperature characteristics. The 2μm band covers several strong OH- absorption peaks and is also in the atmospheric window, which can be widely applied for laser medical, lidar and free space optical communication. With the improvement of the industry of fiber doped with rare earth elements, the gain spectrum of thulium fiber and holmium-doped fiber can cover 1.7μm to 2.2μm. According to Mie scattering, the scattering intensity of near-infrared laser transmission in atmosphere is inversely proportional to the square of the wavelength, hence, the 2μm laser has higher potential in free-space optical (FSO) communication than the conventional 1.55-μm laser. Furthermore, the laser with wavelength greater than 2μm avoiding the molecular absorption peaks of several common gases, such as CO2 and CH4. At present, the research on 2μm fiber laser is mainly focused on the generation of mode-locked pulses with high pulse energy and narrow pulse width. There is still a lack of researches on the generation of high-frequency and high-stability mode-locked pulses with wavelength greater than 2μm. The study of high-frequency and high-stability mode-locked pulses over 2μm band and the characteristics of transmission under turbulent conditions provide a theoretical basis for the future full-band communication, which is of great significance to expand the new band of space laser communication.
Professor Wang Tianshu of Changchun University of Science and Technology has carried out research on 2.07μm actively mode-locked holmium-doped fiber laser with high repetition rate. The research group concentrated on the following studies: Generation of high stability mode-locked pulses with wavelength over 2μm; Generation of ultra-high repetition rate mode-locked pulses with wavelength tunable; 2μm mode-locked laser clock synchronization, modulation/demodulation technology; Propagation characteristics of mode-locked fiber laser in turbulent channel. The research group published “Scintillation index reducing based on wide-
spectral mode-locking fiber laser carriers in a simulated atmospheric turbulent channel” (Optics Letters, 2018, 43(14), as shown in Fig. 1) for the study of partially coherent beams propagation characteristic in turbulent channel. “Propagation characteristics of 2.07μm fiber laser in weak turbulence condition” published in Opto-Electronic Engineering is the research progress of 2μm mode-locked fiber laser generation and modulation/demodulation (As shown in Fig. 2). Recently, the research group published “2-μm Free-Space Data Transmission Based on an Actively Mode-Locked Holmium-Doped Fiber Laser” (IEEE Photonics Technology Letters, 2020, 32(5), as shown in Fig. 3). More research content can be obtained by paying attention to the relevant reports of the research group.
Fig. 1. Comparison of scintillation index and BER between partially coherent beams and coherent beams under different turbulent conditions
Fig. 2. Pulse trains and eye diagram of high repetition rate mode-locked pulse sequence
Fig. 3 Comparison of power jitter between 1.55μm and 2μm fiber laser under different turbulent conditions
This research is supported by the National Natural Science Foundation of China 61975021.
About The Group
Professor Wang Tianshu of Changchun University of Science and Technology has long been engaged in research on the transmission characteristics of fiber lasers and free-space data transmission. The research group undertakes a number of scientific and technological projects at the national and provincial levels such as the Military Commission and the National Natural Fund. More than 60 papers have been published in important optical journals such as Optics Letters，Optics Express，IEEE Journal of Selected Topics in Quantum Electronics，IEEE Photonics Technology Letters and Applied Optics. The research group has more than 20 national patents for invention, and won the first prize for technological invention in Jilin province in 2018. The research results "2μm wideband tunable fiber laser "were evaluated by the third-party achievement evaluation organization to obtain " domestic leading, international advanced "evaluation. A series of breakthroughs have been made in the field of 2μm ultrafast fiber laser for all-fiber femtosecond laser generation, high energy mode-locked pulse generation and high repetition rate mode-locked pulse generation. The study of propagation characteristics of partially coherent beams in turbulent channel has been studied. On this basis, the research group broke through the study of propagation characteristics of 2μm mode-locked fiber laser, and obtained a lot of research results.
Lin Peng, Wang Tianshu, Ma Wanzhuo, et al. Propagation characteristics of 2.07 μm fiber laser in weak turbulence condition[J]. Opto-Electronic Engineering, 2020, 47(3): 190588.