Active Q-switching in Tm:YLF laser based on electro-optic KLTN

摘要

Electro-optic active Q-switching in a TnrYLF laser operating at 1.88 μm is demonstrated using a potassium lithium tantalate niobate (KLTN) crystal as the electro-optic medium. Upon approaching the ferroelectric phase transition temperature, KLTN manifests an exceptionally strong quadratic electro-optic effect. Operation with low driving voltages of 550V on a 3 mm wide and 2mm long crystal were demonstrated. Pulse energy of 1.4 mJ with 17 ns pulse duration was obtained at 1 kHz repetition rate with 9.5W incident pump power. A special trapezoidal configuration of the KLTN crystal was used in order to suppress the acousto-optic oscillations that are generated due to the strong electrostriction manifested in KLTN close to the phase transition temperature which lead to strong instabilities in the laser performance. New EO Q switching mechanism was implemented, in which the resonator gain rather than the loss was shifted between two levels by exploiting the different gain of the Tm:YLF crystal in the σ and π polarizations. This obviated the need for inserting a polarizer in the laser cavity, and allowed the shortening of the laser cavity.