Abstract

We report on the recent advances made in high repetition rate short pulse amplification. At the present time there are basically two different approaches for kHz amplification of femtosecond pulses. The first approach has been demonstrated by Knox et al.¹ and uses a copper vapor laser as the amplifier pump source. Because of the long pump pulse (~30 ns) a multiple-pass dye amplifier is used, producing 1-μJ short pulses at 10 kHz. A fundamentally different approach has been demonstrated by our group.^2,3 We use a short pump pulse of 300-μJ energy and 100-ps duration, delivered by a continuously pumped, frequency-doubled regenerative Nd:YAG amplifier. Because the latter is seeded the same 1.06-μm pulses used to drive our synchronously pumped dye oscillator, a hard synchronization is established between the amplifier pump pulse and the oscillator pulses. The pump pulse energy can therefore be efficiently transferred to the oscillator pulse by means of single-pass dye amplifiers. Five-μJ pulse energies at 1-2 kHz have been obtained, well above the threshold for white-light generation. Part of the white light can be selected and amplified by an auxiliary single-pass dye amplifier. The features of the system and its applications to ultrafast spectroscopy are highlighted.

© 1985 Optical Society of America