Reduction of the threshold of stimulated Raman scattering in Raman-active media introduced into pores of a globular photonic crystal

The characteristics of stimulated Raman scattering in benzene and carbon disulfide introduced in pores of globular photonic crystals-opal matrices formed from close — packed balls (globules) of amorphous quartz (silica) — have been experimentally studied. Stimulated Raman scattering spectra have been excited by giant pulses of the second optical harmonic (532 nm) of a YAG laser. The spectra have been recorded in the direction of mirror reflection from the (111) growth surface of a globular photonic crystal at various angles of incidence (10$^\circ$–70$^\circ$) of laser radiation. It has been shown that the threshold of stimulated Raman scattering decreases sharply (by more than an order of magnitude) at a certain angle of mirror reflection and additional Stokes and anti-Stokes Raman satellites appear in the spectrum. The observed sharp decrease in the threshold of stimulated Raman scattering has been explained by an increase in the spectral density of the electromagnetic field in the surface region of the photonic crystal because of the approach of the spectral position of the stopband of the photonic crystal to the exciting line (532 nm) under variation of the angle of incidence of pump radiation on the (111) surface.