Nonlinear phenomena in synthetic opals

Photonic crystals - the artificial materials with periodic dielectric structure with a period close to the wavelength of electromagnetic waves - are promising materials for nonlinear optics. Two new nonlinear optical phenomena have been found out recently in photonic crystals: photonic flame effect (PFE) and stimulated globular scattering. This paper studies properties of PFE, SGS, and stimulated Raman scattering (SRS), excited in synthetic opal matrices, composed of close-packed silica spheres with diameter from 200 to 320 nm arranged in face-centered cubic lattice. All the samples used demonstrates backward SGS with high conversion efficiency.The absence of the forward SGS for some samples can be explained by the strong attenuation of the laser radiation inside the sample. There are two reasons for this attenuation. One reason is the coincidence of the laser light wavelength with the photonic band gap and the other is incoherent scattering of light on structure defects. Second process is defined by a mean free photon path, which depends on the refractive index contrast.