Elliptical solitons in nonconventionally biased photorefractive crystals

Peng Zhang,Jianlin Zhao,Jingjun Xu,Zhigang Chen,Dexing Yang,Xiaoyu Tan,Yuhan Gao,Cibo Lou,Qian Liu

doi:10.1364/oe.15.000536

Abstract

We theoretically predict and experimentally observe the two-dimensional (2-D) bright solitons in a nonconventionally biased strontium barium niobate (SBN) crystal. A theory describing light propagating in an SBN crystal with a bias field along an arbitrary direction is formulated. Then the existence of 2-D bright solitons in such a crystal is numerically verified. By employing digital holography, the index changes induced by Gaussian beams in an SBN crystal under different biasing conditions are visualized. Finally, skewed elliptical solitons are experimentally demonstrated.

Highlights

Photorefractive spatial optical solitons have been the topic of extensive research in the past decade due to their physical significance and potential applications in beam steering, optical interconnects, and nonlinear optical devices [1, 2]
Some natural questions arise: What will happen when the bias field is along an arbitrary direction? Can such nonconventionally biased schemes support different types of solitons such as bright, dark, vector [7], vortex [8] and discrete solitons? Will new phenomena appear during soliton formations and their interactions? Recently, space charge fields in nonconventionally biased photorefractive crystals have been numerically analyzed by Crognale and Rosa [9]
The index changes induced by a Gaussian beam in an strontium barium niobate (SBN) crystal under different biasing conditions are visualized. 2-D bright elliptical solitons in an SBN crystal with a bias field perpendicular to the c axis of the crystal are experimentally observed

Summary

Introduction

Photorefractive spatial optical solitons have been the topic of extensive research in the past decade due to their physical significance and potential applications in beam steering, optical interconnects, and nonlinear optical devices [1, 2]. Of particular interest are the so-called screening solitons, which attracted most theoretical and experimental attentions because of the accessibility of self-focusing and self-defocusing in the same crystal by reversing the polarity of the bias field and the ease of soliton formations and manipulations, as well as their stability and robustness [2,3,4]. To our knowledge, the directions of the bias fields for obtaining screening solitons are either parallel (for bright solitons [3]) or antiparallel (for dark solitons [4]) to the c axis of the photorefractive crystal. We theoretically predict and experimentally demonstrate the existence of two-dimensional (2-D) bright elliptical solitons in a nonconventionally biased strontium barium niobate (SBN) crystal

Theoretical analysis

Nonlinear index changes and beam propagation

Soliton solution and its properties

Soliton excitation by Gaussian beams

Experimental demonstration

Summary