Optimization of High Reflectivity Measurement by Cavity Ring-Down Technique

The reflectivity of cavity mirror has a great influence on output power and conversion efficiency of laser. Based on pulsed cavity ring-down (CRD) technology, a single wavelength reflectivity measuring system is set up. Comparing the testing curves, the system, whose ring-down cavity is confocal cavity, could accurately determine the reflectivity of a mirror at the wavelength of 946 nm. The average values of ring-down time are 1.5857μs and 0.7950μs respectively. The reflectivity of the concave cavity mirrors is to be 99.7900%, and that of the flat mirror to be 99.7910%, relative error achieves to 10´ . Then the influence of the reflective metrical precision is studied with cavity parameters optimization and cavity length misadjustment. It is suggested that logarithm transformation of oscilloscope should be applied to adjust the optical cavity for improving metrical precision. The results will supply an effective instruct for improving intra-cavity frequency-doubling blue laser performance.