In acetylene lasers operating at 3 μm, the relaxation from the lower laser level to the ground state mainly relies on non-radiative processes such as molecular self-collisions and collisions with the core wall. The vibrational energy levels v1 and 2v2 of ammonia (NH3) are close to the lower laser level of acetylene and allow radiative relaxation to the ground state. By selecting ammonia as the buffer gas, molecular collisions and energy transfer processes can provide a new relaxation pathway for the lower laser level of acetylene, effectively improving laser operation performance.

　　Recently, a research team from the Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences, has, using buffer gases, carried out an innovative and systematic study on improving the conversion efficiency of acetylene-filled hollow-core fiber gas lasers (A-HCFGLs). Choosing a 1.53 μm single-frequency fiber laser as the pump source, the team achieved a 3.9 W single-frequency laser output at 3.1 μm, with a slope efficiency exceeding 35%. The related results were, entitled “Buffer gas enhancing of power conversion efficiency of continuous-wave acetylene-filled fiber gas laser at 3 μm wavelength.”, were published in Optics Express on April 1，2025.

　　In this work, the research team established a rate equation model for the fiber gas laser and investigated the effects of collisional relaxation on laser output under various conditions, including gas pressure, partial pressure ratio, fiber core size, and fiber length. Numerical simulations were conducted to optimize the design of the acetylene fiber gas laser incorporating ammonia as a buffer gas.

　　Based on the model mentioned above, the researchers constructed an experimental platform. Under conditions of a 3:1 acetylene-to-ammonia ratio at a total pressure of 7 mbar, a maximum continuous-wave laser output power of 3.9 W was achieved. Compared with the maximum slope efficiency of 29.5% obtained using pure acetylene in the same experiment, the introduction of the buffer gas increased the slope efficiency to 35.74%, which is the highest efficiency reported to date. This work provides a new research approach for further improving the performance of fiber gas lasers.　　

　　Figure  (a) Experimental setup; (b) Output power curves under different total pressures and gas mixing ratios; (c) Output spectrum at 3 W under a total pressure of 7 mbar with a 3:1 acetylene-to-ammonia mixture.

　　Article website: https://opg.optica.org/oe/fulltext.cfm?uri=oe-33-7-15945&id=569870

　　Contact: CHEN Zhuo 

　　Advanced Laser and Optoelectronic Functional Materials Department, 

　　Shanghai Institute of Optics and Fine Mechanics, CAS 

　　Email: 2863208477@qq.com