Energy transfer enhancement in photorefractive InP:Fe crystals using an auxiliary incoherent beam and a negative thermal gradient

The exponential gain of two-beam coupling in InP:Fe crystals under dc fields is a function of the pump beam intensity at a given temperature. IN this paper, the authors propose two methods to extend the sample volume working under optimum conditions. The first method is based on a negative thermal gradient and the second uses an auxiliary incoherent beam. Theoretical simulations predict an integrated gain of 15 cm{sup {minus}1} and 10 cm{sup {minus}1}, respectively (for {lambda} = 1.06 Mm, {Lambda} = 5 Mm and E{sub 0} = 10 kV/cm) in thick crystals (L = 5 mm). Preliminary experimental results confirm that high gain performances can be achieved by using these methods.