Optical testing of frequency doubling crystals

An optical test was conducted for undoped lithium niobate crystals that will be used for frequency doubling. The test consists of holographically measuring the photorefractive effect near the doubled wavelength as an indication of the vulnerability of the crystal to optical damage. The data consists of temperature dependence measurements of the diffraction efficiency of volume-holographic-phase gradings written inside the crystal in different laser beam powers. The results indicate exponential relationship (Arrhenius dependence) between diffraction efficiency and temperature similar to thermally-activated conductivity. This data, when correlated with crystal performance as a frequency doubler, may be useful to predict performance capabilities of other frequency doubling crystals --Abstract, page ii