Pulsed self-Raman laser operation in Nd:SrMoO4 at 1.57 μm

The goal of our research was the construction of the laser emitting short pulses with high peak power in "eye-safe" region around wavelength 1.5 μm. We use Raman self-conversion of giant pulses at wavelength 1.3 μm in Nd 3+ -doped Raman active crystal SrMoO 4 (diameter 4.4 mm, length 42 mm). Fundamental laser wavelength was obtained using this advanced solid-state medium Nd 3+ :SrMoO 4 , lasing at 1378.1 nm, and pumped at wavelength 752nm by free-running alexandrite laser. High-peak power required for efficient Raman conversion was reached by Q-switching of the Nd 3+ :SrMoO 4 laser by V:YAG solid-state saturable absorber (initial transmission 93% @ 1380 nm). Specially designed resonator mirrors were used to ensure proper feed-back for Raman laser. The resonator pump mirror was concave with 0.5m curvature and with high transmission at 752nm and high reflectivity in the range from 1250nm to 1580 nm; the reflectivity of the output coupler was 3% @ 1380nm and 25% @ 1570 nm. Both mirrors have reflectivity around 1 μm as small as possible to prevent lasing at other Nd 3+ lines. With the described laser system, simultaneous generation of wavelengths 1378.1nm and 1569.8nm was obtained. The single pulse output energy 0.8mJ at 1569.8nm was reached. The length of the generated pulse at this wavelength was measured to be 8.7 ns (FWHM). These values correspond with the peak power of 92 kW in eye-safe region.