  In this manuscript we report experimental demonstration of nonlinear
frequency conversion at several optical frequencies in a whispering-gallery
mode resonator (WGMR). Due to the enhancement of nonlinear interactions inside
a WGMR, interaction of a 1064 nm pump field with a LiNbO3 disk produced a weak,
but measurable non-phase matched 532 nm second harmonic field at room
temperature (>100C below the phase-matching temperature), for pump powers of a
few tens of mW. For higher pump powers, we observed the generation of four
additional fields at 545 nm, 559 nm, 573 nm, and 587 nm. The relative spectral
shift between two consecutive fields corresponds to a 455 cm^-1 vibrational
mode in LiNbO3 crystal. Our preliminary analysis indicates that these fields
are the result of a multi-phonon hyper-Raman scattering, in which two photons
of the pump field are converted into one photon of a higher-frequency field and
one or several optical phonons.
