Laser-induced quasi-phase matching in thermally poled glasses

Quasi phase matching was induced within a few minutes by optical means in a thermally poled glass sample. The spatial modulation of chi((2)) that was induced by two-photon absorption of the sample subjected to an intense sinusoidal pump intensity pattern resulted in a chi((2)) grating. The second-harmonic generation produced by a probe beam was diffracted in specific directions by this chi((2)) grating, thus providing a way to monitor its inscription inside the glass. This chi((2)) grating is extremely stable at room temperature and in ambient laboratory conditions. During the process of inscription, a linear index grating was also induced. It was not stable, and it relaxed rapidly.