ZnSe:Cr~(2+) laser coherently pumped by Er:YAP 1.66 μm laser or Tm: YAP 1.97 μm laser

摘要

Tunable mid-infrared laser radiation sources are of interest for many applications in spectroscopy, ranging, remote-sensing, medical diagnosis and treatment and also for pumping nonlinear (OPO) and laser materials. The ZnSe:Cr~(2+) is a promising laser active material for lasing in the range of 2-3 μm. Up to now number of sources have been used for pumping ZnSe:Cr~(2+) active medium: Er-fibre laser, color-center laser, Co:MgF_2 laser, Tm lasers, and Raman-shifted Nd:YAG laser. In our study we have demonstrated, characterized and compared ZnSe:Cr~(2+) laser coherently pumped either by flashlamp-pumped Er:YAP (wavelength 1.66 μm) or diode pumped Tm:YAP (wavelength 1.97 μm) laser radiations. For the case of ZnSe:Cr~(2+) laser pumping by wavelength 1.66 μm, the Er:YAP laser was constructed. From the measured output radiation characteristics followed that the maximal ZnSe:Cr~(2+) laser output pulse energy was 5.5 mJ (slope efficiency 23%), and the length of pulse 120-160 μs. With the help of dispersive prism inside the resonator, the generated laser radiation was tunable from 2100 nm to 2450 nm with only 2 times drop in laser efficiency. The temporal profile and spatial structure of the generated laser beam were measured. Consequently, the diode-pumped Tm:YAP laser was constructed for coherently pumped ZnSe:Cr~(2+) laser. LIMO laser diode (40 W) was used for longitudinal pumping of Tm:YAP laser. The output characteristics and tuning curves were measured for various ZnSe:Cr~(2+) laser resonator arrangements and also for various pumping radiation conditions in pulsed regime (pulse duration, repetition rate, duty cycle). The maximal obtained ZnSe:Cr~(2+) laser output pulse energy was 0.35 mJ for the Tm:YAP pump pulse energy 13.5 mJ (pulse radiation 5 ms, repetition rate 20 Hz). The generated laser radiation was tunable from 2100 nm to 2450 nm. The temporal profile and spatial structure of the generated laser beam were measured.