Efficient, high-repetition rate, blue source using a compact CR:LiSAF laser

Summary form only given. We report a compact, directly diode-pumped Cr:LiSAF laser as an alternative pump source. This laser has an electrical-to-optical efficiency in excess of 1% and produces transform-limited pulses of ∼150 fs in duration at ∼865 nm. The average power is 35 mW and the repetition rate is ∼250 MHz, which implies modest peak powers of less than 1 kW. At these low power levels, efficient frequency doubling usually requires complex arrangements, especially if the pulse duration is to be preserved. In this paper we describe the use of a relatively thick doubling crystal in a single-pass, extra-cavity arrangement. Although the second harmonic pulses suffer temporal broadening, this represents an effective way to achieve efficient frequency conversion in a simplified configuration. The nonlinear crystal was potassium niobate (KNbO3) cut for non-critical phase matching at 860 nm and 22°C.