Characterization and active stabilization of a harmonically modulated continuous-wave Nd:LiYF4 laser

Abstract

A continuous‐wave harmonically modulated Nd:LiYF₄ laser has been built, which offers a high degree of mechanical, electrical, and optical stability. Different operating regimes of this system are outlined. For reliable operation, the cavity length has to be accurately matched to the frequency of the mode‐locker driver, much more so than for a fundamentally modulated system. For this purpose, a computer‐controlled length‐stabilization system is developed. This active stabilization scheme, which compensates thermal and mechanical drifts of the resonator and eliminates the warm‐up time of the laser, ensures a stable optical pulse train at the fundamental axial mode spacing of the resonator. The stabilization system is fully compatible with other more commonly implemented analog feedback mechanisms. It should find applications in most harmonically modulated solid‐state lasers, and possibly also in fundamentally modulated ones. Compared to the latter, the actively stabilized harmonically modulated laser generates pulses that are shorter and have less jitter.