New Varieties of Lithium Niobate for Optical Communication

The modulation and/or Q switching of laser radiation has often been accomplished by using the electrooptic properties of crystals such as lithium niobate. Until recently the photorefractive effect, an internal electric field due to the photoionization of iron and other transition metal impurities, has drastically limited the usable intensity of the laser beam. It has now been found that magnesium-doped lithium niobate has a much higher photoconductivity than the undoped crystal, greatly reducing the photorefractive effect and permitting the modulation of beams of higher intensity. The advantages and drawbacks accompanying the use of magnesium-doped crystals will be discussed.