Nonlinear generation of ultrashort infrared pulses

Wavelength-tunable ultrashort laser pulses in the picosecond and femtosecond time range have become readily available and have found wide ranges of applications. This has been largely due to the development of broad-band tunable laser sources and powerful pumping sources. The technology of ultrashort pulse generation has become highly developed, but most of the development has been concentrated in the visible and near infrared spectral ranges of wavelengths shorter than 2 μm. In the broad infrared spectral range, picosecond and femtosecond laser pulses have not been so readily available except for a few specific wavelengths. The primary difficulty has been the lack of suitable laser medium in the infrared spectral range. This is particularly true when ultrashort and wavelength-tunable laser pulses are sought for. This difficulty can be circumvented by employing nonlinear frequency conversion techniques. An optical parametric oscillator (OPO) with a resonant cavity can be synchronously pumped for efficient frequency conversion. The general characteristics and the current development of synchronously pumped OPO´s for efficient generation of picosecond and femtosecond wavelength-tunable infrared pulses is discussed