Development of single-mode diode pumped cr: Lisaf lasers

In this thesis, we have investigated continuous-wave (CW), Q-switched, Q-switched mode locked and mode-locked lasing operation in a single-mode diode (SMD) pumped Cr:LiSAF laser. The 1.5% Cr-doped, 10 mm long Cr:LiSAF gain medium was pumped by two 660 nm, 150 mW SMDs from both sides. Usage of low-cost SMDs as pump sources enabled the construction of compact, efficient and cost-effective laser system. A simple x-type laser cavity was employed in the cw lasing experiments. We have tested the cw lasing performance by using output couplers (OCs) with transmissions ranging from 0.07 % to 0.75 %. The best output performance was obtained using the 0.75 % OC, where cw lasing threshold of 20 mW, cw power up to 126 mW, and a slope efficient of 37 % was achieved. A saturable Bragg reflector (SBR) with a modulation depth of 0.8 % was inserted into the cavity for Q-switched and Q-switched mode-locked experiments. In Q-switched regime, pulses as short as 2.2 µs, with average and peak powers of 51 mW and 0.35 W were demonstrated at a repletion rate of 43.4 kHz. Afterwards, Q-switched mode-locked operation was performed and mode-locked pulses were observed in the Q-switched envelope. The spectral width of the pulses supported pulsewidths in the 758-823 fs range. The Q-switched envelope had a repetition rate of 56.75 kHz. We have also demonstrated tuning of the Q-switched mode-locked laser pulses from 821 nm to 888 nm, using an intracavity birefringent tuning plate. The peak power of the pulses are estimated to be 6.79 kW for 845 nm at stable condition. The 850 nm saturable Bragg reflector has been replaced with the 800 nm, 1.6 % modulation depth, and new mirrors with negative dispersion are added to achieve mode-locked pulses. The peak power obtained for these pulses is around 6.7 kW and the repetition rate of the pulses is about 129 MHz. To our knowledge, these results represent the first detailed investigation of Q-switch and Q-switched mode-locked operation in Cr:LiSAF gain medium.