Coherent CW image amplifier and oscillator using two-wave interaction in a BaTiO3-crystal

Abstract

A BaTiO3 crystal was used to amplify an image illuminated by an Ar-laser. The amplification mechanism is two-wave mixing in an electrooptic crystal, usually called dynamic holography. We achieved gain factors of 4000 with pump powers of 150 mW and holographic resolution. As the interaction between signal and pump wave is not effected through excited states of the crystal, the amplification process is virtually noise free. This has to be traded in with slow response, 0.1-1 s. To demonstrate the high optical quality of the amplifier, it was incorporated in a ring resonator as gain medium. It was possible to excite pure discrete transversal modes of higher order. That reveals the high optical homogeneity of the crystal over the mode cross-section of > 1 mm. The coupling process of the pump with the two counter-propagating waves forming the standing resonator wave is not symmetric. Consequently a travelling wave develops in the resonator. © 1983.