Correlation of the Damage Behavior of High Power Continuous Wave Laser Hybrid Mirrors with Total Losses
SPIE Laser Damage
Novel high power laser applications such as laser scanning modules require mirrors with specific optical and mechanical characteristics. The mirrors reflectance must be high in a broad range of angles and for different polarizations. Additionally, due to the high-speed rotation of the components a high mechanical rigidity is required. Moreover, the mirrors reach high temperatures and thermal stress while precisely redirecting the high power continuous wave (cw) lasers radiation. Therefore, metal-dielectric-hybrid mirrors with appropriate thermal properties are often used in such devices, and the determination of the cw damage behavior is of major interest. We investigated the damage behavior of different hybrid mirror batches with similar manufacturing characteristics under cw-laser irradiation. The mirrors were irradiated at an angle of 45° with laser radiation at a wavelength of 1030nm and power levels between 40W and 6000W. We applied an adapted measurement procedure with respect to the limited sample diameter of 25mm and the comparably large modified area if a damage occurs. Afterwards, we studied the resulting survival curves of the mirrors. Subsequently, we compared the rise of the damage probability curve in dependence of the incident power with the optical characteristics of the samples. The damage properties with different loss mechanisms of the mirrors were correlated. The overall losses were determined using cavity ring-down spectroscopy, and we separately determined the scattered light using a total scattering device. Eventually, a connection between the steepness of the damage probability curve and the variance of the opt ical losses within one mirror batch was observed.