Research News

Researchers Develop High-efficiency Mid- and Long-wave Optical Parametric Oscillator Pump Source

Feb 13, 2023

Widely tunable mid- and long-wave infrared (8-12 μm) laser belongs to the atmospheric window range and the human eye safety range. It is widely applied in the field of Lidar.

A research team from the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences (CAS) has developed a high-efficiency mid- and long-wave optical parametric oscillator pump source: Ho:YAG laser, which achieves high-efficiency 2.1 μm laser output by scanning and optimizing the pump laser wavelength.

The study was published in Scientific Reports on Jan. 18.

A tunable Tm:YLF laser is the pump source of the Ho:YAG laser. According to the temperature tuning characteristics of volume Bragg grating (VBG), the wavelength of Tm:YLF laser's continuous tunability ranges from 1906.04 to 1908.83 nm, corresponding to a linewidth of less than 0.41 nm. By scanning and optimizing the wavelength of the pump light, the Ho:YAG laser output with a light-to-light conversion efficiency of 59.12% and a slope efficiency of 68.26% was achieved under the center wavelength of the pump source of 1907.36 nm.

They used the Ho:YAG laser as the pump source of ZnGeP2 optical parametric oscillator (ZGP-OPO) and obtained a high-efficiency tunable long-wave infrared laser under type I phase matching, with a tuning range of 8.02-9.15 μm.

This research lays the foundation for the development of all-solid-state mid- and long-wave lasers and is expected to expand Lidar applications.

Figure 1 (a) Experimental setup of the Ho: YAG laser pumped by Tm: YLF laser. (b) Wavelengths at different VBG temperature. (c) Measured ZGP wave-tuning idler spectrum. (d) Absorption spectrum of 0.8 at.% doped Ho: YAG at 20°C and output power. (Image by AIR)