Abstract

The recent years witnessed a renewed interest in second-harmonic generation (SHG), Nevertheless, SHG is still limited because of the basic requirement for phase-matching between the fundamental and the second-harmonic waves, which is usually not met because of dispersion, The most common method to overcome the phase-matching problem is to use the crystal birefringence. However, this and similar solutions restrict the frequency range in which the harmonic generation can be obtained. There is another way to obtain quasi-phase-matching by an "artificial" spatial modulation of the optical nonlinearity. Such a modulation was produced in LiNbO₃ and other crystals by a periodic changing of the crystal orientation during their growth, or by other irreversible techniques. This again gives SHG only for a specific input wavelength.

© 1993 Optical Society of America