Spontaneous parametric light scattering in spatially inhomogeneous nonlinear media based on photonic crystals

The emission spectra of nonlinear media with periodical modulation of the second-order susceptibility that are based on synthetic opals infiltrated by Ba(NO₃)₂, LiIO₃, and KH₂PO₄ are studied using radiation with λ = 400 and 407 nm for excitation. The spectral angular distribution of the emission in the range of 420–650 nm is revealed, as well as the dependence of its spectrum on the photonic stop-band parameters and the exciting radiation characteristics. The emission spectrum of samples with a low dielectric contrast has the shape of a symmetric band with a maximum at 525 nm and a half-width of about 100 nm. The observed emission is interpreted as spontaneous parametric light scattering in a spatially inhomogeneous nonlinear medium.