SECOND-HARMONIC WAVE GENERATING ELEMENT

摘要

An element for generating second-harmonic waves of a short wavelength from a fundamental wave emitting from a semiconductor laser and the like. The element includes a substrate made of a ferroelectric crystal, a second-harmonic wave generator for generating a second-harmonic wave from a fundamental wave entered therein, and periodically arranged portions formed in a front stage region and a rear stage region of the element. The periodic portions or structures, each have pairs of parts or regions of a high optical refractive index and of a low optical refractive index so as to confine the fundamental waves in the second-harmonic wave generating portion. These regions have various kinds of material diffused or introduced therein and of a thickness. According to another example of the element, the sign of a nonlinear optical coefficient of the region is periodically reversed and the region satisfies a quasi-phase-matching condition.