Abstract

The scope of this paper is to revisit the use of quadratic crystals cut for second harmonic generation (SHG) with type II phase-matching in view of all-optical processing of light signal. The investigations on this topic mainly focused in the past years on the possibilities opened by cascading of quadratic nonlinearities in phase-mismatched conditions [1]. The goal of this paper is to remind the reader that various types of optical processing are achievable with sum and difference frequency generation in phase-matched position without the requirement for cascaded nonlinearities. In a first part we will report few examples of the use of difference frequency generation (or down conversion) for signal processing. In a second part we will show that type II SHG with unbalanced fundamental inputs may lead to coherent amplification or transistor like operation.

© 1998 Optical Society of America