Inverse Raman Scattering by Polaritons in LiNbO3 Single Crystals

Experimental studies of IRS by polaritons in LiNbO₃ are reported for the first time. In compliance with the classification of IRS-scattering geometries by polaritons in uniaxial crystals [3] for different polarisation directions of laser and anti-Stokes continuum two A₁-type polaritons and also E-type-polaritons of the upper and the lower ordinary dispersion branches, respectively, could coherently be generated. Introducing a new polariton specific excitation state instead of the mechanic vibration the shortened IRS equations without small signal approximation are solved in the stationary case and for “responseless” polariton fields. The increase of the laser field and the decrease of the anti-Stokes field show for α_px ? 1 the same behaviour as Stokes growth and laser depletion, respectively, in the case of SRS by dipole inactive levels. Model calculations show the necessity of the used intra cavity arrangement for photographic registration of IRS-polariton spectra.