Investigation of the dynamics of a versatile laser amplifier upon fast modulation of its CW and pulsed seed sources

Abstract This paper presents an investigation of the dynamics of a versatile thin-disk multipass laser amplifier (TDMPA) with two seed sources. The study focused on the system’s transient response, analyzing the amplified instantaneous power during and shortly after fast modulation of the individual seed powers. For switching times shorter than the amplifier’s characteristic response time, changes in the total seed power led to retardation and overshooting effects , which are attributed to the gain-saturation dynamics of the active laser medium. An analytical formula to express the dependence of the characteristic response time on the input and output powers and the specific TDMPA architecture was derived and validated. This provides a practical guideline for choosing seed-power switching times that avoid transient overshooting and retardation effects . For pump powers between 599 and 1446 W, and depending on operation conditions, the TDMPA under consideration was measured to exhibit a gain-saturation response time ranging between approximately 30 and 90 µs.