Femtosecond Cr:Colquiriite Lasers Pumped by a Single Tapered Diode Laser

Abstract

Ti:Sapphire lasers could provide tunable femtosecond pulses in the 680-1180 nm region; however, due to the requirement of expensive green pump sources, its current cost sets a barrier to its widespread adoption. As an alternative, Cr :Colquiriites (Cr:LiCAF, Cr:LiSAF, Cr:LiSGaF) also possess broad gain bandwidths and their total cw tuning range cover the 720-1110 nm region. Moreover, their broad absorption bands around 650 nm enable direct diode pumping by low-cost red laser diodes. However, so far the limited brightness of red diodes required combination of four to six pump diodes to reach reasonable output power levels from Cr :Colquiriites. This complex pumping geometry increases cost and causes stability issues in long-term operation. In this study, we report compact, low-cost and efficient Cr:Colquiriite lasers pumped by a single 1.2 W tapered laser diode at 675 nm. In continuous wave laser operation, output powers of 500 mW and 410 mW together with slope efficiencies of 47% and 41% were demonstrated from Cr:LiSAF and Cr:LiCAF, respectively. In cw mode-locked operation, sub-100-fs pulse trains with average power between 200 mW and 250 mW were obtained at repetitions rates around 100 MHz. These results indicate that tapered diodes in the red spectral region are likely to become the standard pump source for Cr:Colquiriite lasers in the near future. Moreover, the simplified pumping scheme might facilitate efficient commercialization of these low-cost systems, bearing the potential to significantly boost applications of cw and femtosecond lasers in this spectral region.