Mode-locking of a Cr2+: ZnSe laser using a PPLN non linear mirror : Theoretical modelling and cavity design

Here, we propose to apply to Cr²⁺:ZnSe an original mode-locking technique, using an intracavity second order nonlinear mirror, and efficiently demonstrated on near-infrared (lambda=1 mum) laser sources. Indeed, efficiency and reliability reached by second order non linear crystals, such as PPLN, allow a transposition of the nonlinear mirror concept from near-infrared to mid-infrared laser sources. We investigate numerically Cr²⁺:ZnSe mode-locking by intra-cavity nonlinear mirror, based on a PPLN crystal. We explore the effects of different parameters on the laser temporal dynamics, and show that, depending on various parameters, the laser can display a CW, or pulsed (Q- switched and/or mode-locked) behavior. The simulation is carried out for the characteristics of a Tm³⁺:YLF pumped CW Cr²⁺:ZnSe laser available in our lab. We numerically show the possibility of mode-locking in the picosecond regime, with pulse durations around 100 ps, and study the dynamics and stability of this behavior.