Investigation of Optical Power Tolerance for MEMS Mirrors

Optical power tolerance on micromirrors is a critical aspect of many high-power optical systems. Absorptive heating can negatively impact the performance of an optical system by altering the micromirror´s curvature during operation. This can lead to shifts in the beam waist locations or imaging planes within a system. This paper describes a scheme to measure the impact of mirror heating by optical power and determine the power tolerances of micromirrors with gold and aluminum coatings using a 532-nm laser. Results are compared with an analytical model of thermally induced stress and optical absorptive heating. Experimental data shows that gold-coated mirrors are able to handle 40 mW of optical power with a beam waist displacement of less than 20% of the output Rayleigh length, while aluminum-coated mirrors can tolerate 125 mW. Measured data along with modeling suggest that, with proper metal coating, optical powers greater than 1 W should not adversely affect the system performance.