Collisions between two dimensional quadratic spatial solitons in PPLN

Description/Abstract

Self-guided waves (spatial solitons) that can be excited in quadratic nonlinear media have been extensively studied for their potential applications in ultra-fast all-optical processing. We have previously reported the use of solitary waves collision in a KTP crystal to experimentally demonstrate all-optical switching of infrared picosecond pulses. Up to now, the intensity required to obtain self-trapping of a beam remained at a high level. This has been due to the lack of nonlinear crystals which combine the attributes of a large nonlinearity and phase-matching capability at experimentally convenient wavelengths. The availability of Periodically Poled Lithium Niobate can circumvent this difficulty. Two-dimensional spatial solitary waves in PPLN have been predicted theoretically and simulated numerically. In this communication we will report their experimental observation and for the first time their interaction in a 15mm long crystal. Then we will compare solitary wave behaviour in KTP and PPLN, in particular self-trapping intensity threshold versus phase mismatch. We will also compare experimental data with the results of our computations modelling. In a last part we will show our first experimental results about 2D quadratic soliton collision in a PPLN crystal. Finally we will discuss the advantages of choosing PPLN to realise all-optical devices using solitary wave interactions.