Non-linear optical crystal element

摘要

A non-linear optical crystal element preferably of BBO or KDP arranged within a resonator for generating a light beam in the wavelength range of UV rays based on a radiated light beam of a basic wave. The non-linear optical crystal element is preferably hexahedral-shaped and has a protective film on its surface. The protective film is made up of at least two layers arranged on an incident surface and an outgoing surface of the non-linear optical crystal element. The layer of the protective film directly contacted with the incident surface or the outgoing surface is formed by ion plating.