Abstract

Ti:sapphire lasers routinely generate tunable infrared femtosecond pulses, and regenerative amplification can raise the pulse energies to the millijoale level when these lasers are pumped with frequency-doubled Q-switched Nd:YAG/YLF lasers or to the microjoule level at up to 200 kHz when only one (argon-ion) pump laser is used for both the oscillator and the amplifier.¹ Unfortunately, the 3-μs upper-state lifetime of Ti:sapphire necessitates a relatively high pump power. Cr³⁺:LiSrAlF₆ (Cr:LiSAF) is an alternative amplifier medium², with absorption bands suitable for argon-ion or diode-laser pumping, and its upper-state lifetime of 67 μs implies a significantly lower pump power requirement and higher pulse energies. We report here a Cr:LiSAF regenerative amplifier operating at repetition rates up to 20 kHz that provides pulse energies up to 14 μJ for only 3 W of 488-nm pump power. Thus a low-cost-tunable femtosecond Ti:sapphire-oscillator/Cr:LiSAF-amplifier system delivering ~500 mW at 80 MHz and >10 μJ at 10 kHz may be pumped by <10 W all-lines argon-ion power. For real-world applications, however, diode-pumped lasers are clearly more appropriate. Having reported the first picosecond³ and femtosecond⁴ pulse generation from direct diode-pumped Cr LiSAF lasers, we now report what we believe to be the first all-solid-state, diode-pumped tunable femtosecond regenerative amplifier.

© 1995 Optical Society of America