Linear and nonlinear optics of synthetic opal

We report the results of an experimental study of synthetic opal composed from silica spherical particles. Immersion spectroscopy methods were used to inspect the "photonic forbidden zone" and the peculiarities of Bragg reflection in the material. A temporal response of luminescence from artificial opal excited by nitrogen laser UV pulses at room and liquid-nitrogen temperatures was examined. The afterglow with the decay time to about 1 second was found to appear at about 135 K. The temperature dependence of luminescence is of importance for explanation of the surprising effects of stimulated emission in a single nano-sized SiO2 globule and second harmonic generation in the material under high-power excitation from Ti:Sapphire femtosecond laser.