Amplification of ultrashort pulses with a single-pass cryogenic Ti:sapphire amplifier at 80MHz repetition rate

In this report, we demonstrate a single pass power amplifier for sub-7 fs pulses working at any repetition rate larger than the inverse lifetime of the upper laser level. The output from a Ti:sapphire mode-locked laser is focused into a Ti:sapphire crystal together with CW radiation of a frequency doubled Nd:YVO₄ laser. The amplification crystal is cooled by a liquid nitrogen cryostat to avoid thermal lensing. Two different Ti:sa oscillators are used for seeding. A maximum gain of 3.8 is obtained with 100 fs pulses, currently limited by available pump power. In the amplification of ~8 fs pulses, the original output power of 510 mW is amplified up to 1.4 W, giving a maximum gain of 2.6. The smaller gain with Venteon laser is explained by a reduced overlap between the Ti:sa gain spectrum and the seed laser spectrum. The shortest output pulse is compressed by a home-built chirped-mirror compressor and its pulse width is measured. To the best of our knowledge, this is the highest average power obtained with ~8 fs pulses at this repetition rate range.