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

Abstract

Recently, more and more applications require amplifier systems delivering high power, short-pulsed radiation with the full repetition rate of the mode-locked oscillator. In the frequency domain, the output spectrum of the stabilized mode-locked laser consists of equidistant narrow lines separated by the laser repetition rate, often called “frequency comb”. So far, to drive highly non-linear processes directly by frequency combs requires special efforts because of the limited average output power from the mode-locked oscillator. Passive cavity amplifiers have been built to generate frequency combs in the ultra-violet region by high-order harmonics generation. For these applications, power amplifiers that can amplify short pulses from the oscillator will be an ideal tool to further improve available pulse energy at high repetition rates. In frequency comb applications, extra phase noise that is added from the amplifier has to be minimised to preserve pulse-to-pulse phase coherence. In the time domain, phase-locked amplifier system may deliver pulse trains with identical intra-pulse electric field shape. With sufficiently high pulse energy and short pulse width, it is possible to investigate carrier envelope phase dependent phenomena, such as electron emission by field ionisation and high harmonics generation. In these experiments, it is sometimes advantageous to have a high repetition rate system to obtain enough statistics for rare events in short measurement times.