Picosecond optical parametric oscillators and their applications in absorption spectroscopy of fast processes

A comparative analysis is made of absorption spectrometers utilizing superluminescent and cavity optical parametric oscillators (OPOs) emitting picosecond and subpicosecond pulses. The best time resolution (1psec) has been achieved using a synchronously pumped subpicosecond OPO. However, the most universal multipurpose spectrometers used at present are as follows: a two-channel spectrometer based on a superluminescent OPO utilizing KDP and LiNbO₃ crystals and pumped by the second harmonic from a single-pulse picosecond YAG:Nd³⁺ laser with passive mode locking (time resolution 10–20 psec) and a twochannel spectrometer based on a superluminescent OPO utilizing KDP and DKDP crystals and pumped by the second harmonic of a single-pulse picosecond phosphate glass laser (time resolution 2–3 psec). The latest results are given of investigations of the processes of energy migration in chromatophores of photosynthetic bacteria and of photoexcitation relaxation processes in molecules of polymethine and cyanin dyes, carried out using picosecond absorption spectrometers developed on the basis of OPOs and microcomputers at Vilnius State University.