<title>Collisions between two-dimensional quadratic spatial solitons in PPLN</title>

Abstract

Self-guided waves 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 IR 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. 2D 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 behavior in KTP and PPLN, in particular self-trapping intensity threshold versus phase mismatch. We will also compare experimental data with the reslut of our computations modeling. In a last part we will show our first experimental result about 2D quadratic soliton collision in a PPLN crystal. Finally we will discuss the advantages of choosing PPLN to realize all- optical devices using solitary wave interactions.