Device and method for measuring thermal load caused by energy transfer upconversion in laser gain crystal

A method for measuring a thermal load caused by ETU in a laser gain crystal, wherein the method uses a device for measuring a thermal load caused by ETU in a laser gain crystal, and the device comprises a single-frequency laser and a power meter, wherein an output from the single-frequency laser is injected into the power meter, and an output power of the single-frequency laser be measured by the power meter;

• and wherein
• the method comprises the following steps:
• increasing pump power of the single frequency laser from a predetermined initial power value till the single-frequency laser emits light, recording a pump power value at this moment as a pump power threshold;
• and repeating the increasing and the recording to obtain multiple pump power thresholds;
• calculating an average pump power threshold based on the multiple pump power thresholds;
• obtaining cavity parameters of an optical resonant cavity of the single-frequency laser;
• obtaining thermal focal lengths on the tangential plane and sagittal plane of the laser gain crystal inside the single-frequency laser by substituting the average pump power threshold and the cavity parameters into thermal lens focal length formulas for the tangential plane and the sagittal plane;
• obtaining individual ABCD transfer matrices of the laser gain crystal on the tangential plane and the sagittal plane based on the thermal focal length on the tangential plane, the thermal focal length on the sagittal plane, and the cavity parameters;
• obtaining a first thermal load at the average pump power threshold based on the ABCD transfer matrix of the laser gain crystal on the tangential plane, the ABCD transfer matrix of the laser gain crystal on the sagittal plane, the average pump power threshold, and stability conditions of the optical resonant cavity;
• and
• obtaining a second thermal load caused by ETU at the average pump power threshold based on the first thermal load at the average pump power threshold.