Coherent anti-Stokes Raman scattering of two-phonon complexes in diamond

Coherent anti-Stokes Raman scattering (CARS) associated with the second-order Raman process has been confirmed in diamond. Frequency dependence of CARS was analyzed using two-color synchronously-generated picosecond pulses. Resonance enhancement of chi((3)) was observed at an energy shift corresponding to the overtone Sigma branch (K point) phonon, as well as the fundamental Raman-active Gamma((25+)) phonon. The excitation spectrum of CARS at the two-phonon resonance region showed dispersive dependence, reflecting the interference of resonant CARS and nonresonant four-wave mixing scattering.