Abstract

Several spectroscopic techniques such as Coherent Anti-Stokes Raman Scattering, femtosecond stimulated Raman spectroscopy and broadband surface sum-frequency generation require the synchronization between independently tunable narrowband picosecond pulses or between picosecond and femtosecond pulses. Picosecond optical parametric oscillators offer wide tunability and high optical power, but they suffer from a complex architecture and cannot be used in experiments requiring mixing of picosecond and femtosecond pulses. On the other hand, femtosecond sources are becoming more and more compact and reliable, and they can be successfully employed in the above spectroscopic configurations if equipped with suitable “spectral compressor” devices converting efficiently femtosecond into picosecond pulses. It is not easy however to have at the same time an efficient conversion and a simple device [1], A recently proposed solution consists in exploiting a second-harmonic-generation (SHG) process in the presence of high group-velocity-mismatch (GVM) between the fundamental frequency (FF) and the second harmonic (SH) pulse [2].

© 2009 IEEE