Generation of the second optical harmonic in porous-silicon-based structures with a photonic band gap

Efficient generation of the second optical harmonic is observed experimenta lly in a multilayer periodic structure based on porous silicon. The second- harmonic signal is much stronger than the signal from a uniform porous sili con layer or from the single-crystal silicon substrate. The orientational d ependence of the second-harmonic signal is isotropic. The second-harmonic i ntensity as a function of the reflection angle reaches a maximum in the dir ection corresponding to the minimum phase detuning in a multilayer periodic structure. (C) 1999 American Institute of Physics. [S0021-3640(99)00404-1] .