Sub-50 ps pulses at 620 nm obtained from frequency doubled 1240 nm diamond Raman laser.

We report a monolithic 1240 nm diamond Raman laser producing pulses with duration of 42-62 ps at 100 kHz repetition rate, and maximum average power of 246 mW. The Raman laser is formed by a 0.5-mm thick planar diamond, coated on both sides and pumped by ~100 ps pulses from a Q-switched 1064 nm laser. The maximum conversion efficiency from 1064 nm to 1240 nm was about 25%. The 1240 nm signal was frequency-doubled in single-pass configuration through a 10-mm long LBO crystal, enabling generation of pulses with a duration of 29-46 ps at 620 nm. The maximum average power at 620 nm was 128 mW, and the maximum conversion efficiency from 1240 nm to 620 nm was 50%. The Raman laser provides an efficient and flexible way to extend short pulse operation to wavelengths in spectral domains difficult to reach, such as 620 nm and in addition provides a simple pulse shortening mechanisms.