Recently, researcher Li Gang and researcher Jin Yuqi from the Chemical Laser Research Room (Room 7) of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences have made new progress in the research of thin slice laser beam quality control, put forward a new method to continuously output the thin slice laser within the full pump power range and keep the beam quality close to the diffraction limit, and conducted in-depth research on its beam quality control mechanism.
Thin slice laser is a new type of semiconductor pumped solid-state laser with a thin crystal as the gain medium. The chip laser has the characteristics of high average power, high pulse energy and high beam quality at the same time. It has important application prospects in EUV light source, optical frequency comb and attosecond pulse generation, laser micromachining and national defense fields. However, the technology of multipass pumping chip module, which is the core of the chip laser, has been monopolized by foreign countries for many years, and the 72 pass pumping module is banned from sale in China.
In this work, the researchers put forward a scheme of multi pass pumping for thin plate laser, designed and manufactured a 72 pass pumping module with independent intellectual property rights, and developed a method to keep the beam quality of thin plate laser output laser at the diffraction limit within the full pumping power range. The core of this method is to combine a thin film polarizer and a quarter wave plate into a new type of output coupler, so that the output coupling ratio of the laser resonator can be adjusted continuously and linearly. By tuning the output coupling ratio of the resonator in real time, the beam quality close to the diffraction limit (M2<1.2) is obtained in the whole range of incident pump power, and the average output power exceeds 210W. The researchers gave the beam quality control mechanism through the simulation of the diffraction loss of the resonator. For resonators similar to those that realize fundamental mode transverse output through diffraction loss, the continuous variable output coupler has a good application prospect in enhancing the output performance of thin slice lasers, which lays a good foundation for the development of kilowatt class nanosecond lasers and joule class picosecond laser amplifiers in the future.
The team has made a series of research progress in the development of chip lasers after years of technical breakthroughs, including the active alignment technology of the chip multi-pass pump module (Optik, 2018), the porous foam structure cooling array system for the chip gain crystal (Optik, 2020), the latest generation of 72 pass chip pump module and 100 kHz high power cavity emptying chip nanosecond lasers (Optics Express, 2022), 100 fs Kerr lens mode-locked sheet laser based on 72 pass pump module (China Laser, 2022), etc.
The relevant research achievements are entitled "Resolutors with a continuously variable output coupling rate to enhance output performance of Yb: YAG thin disk lasers", which was recently published in Optics Express. The first author of this work is Dai Longhui, a 704 group doctoral student in our institute. The above work has been supported by Dalian Science and Technology Innovation Fund, Dalian Institute of Chemical Physics Innovation Fund and other projects.
Source: Dalian Institute of Chemical Physics, Chinese Academy of Sciences
