Stabilisation, on the basis of narrow optical resonances, of the frequency of a laser continuously generating ultrashort pulses

It is proposed that narrow optical resonances be employed as reference points in the stabilisation of the frequency components of a laser continuously emitting ultrashort pulses. Such a laser has a broad spectrum of stable frequency components and a high pulse power, which permits a sharp increase in the frequency-conversion efficiency. A system for the stabilisation of a Ti:sapphire laser generating ultrashort pulses is examined. This system is based on a two-photon absorption resonance as a result of the 1S — 2S transition in the hydrogen atom.