Abstract
We present numerical and experimental analyses showing the formation of (2+1D) spatial photorefractive solitons at visible wavelengths in electrically biased lithium niobate crystals for ordinary and extraordinary light polarizations. Similarly sized self-trapped beams are observed for both polarizations, despite the polarizationdependent electro-optic coefficients. The tensorial character of the photovoltaic effect is shown to play a key role. The soliton-induced waveguides are able to properly guide telecommunication wavelengths. Finally, a higher degree of anisotropy is observed for ordinary polarized solitons for specific electro-optic configurations, which reveals the presence of the photorefractive field component perpendicular to the applied field. Experimental results are confirmed by a time-dependent numerical model.
Highlights
In this work we present the possibility of using ordinary polarization to create bright spatial solitons and efficient circular waveguides in LiNbO3
In order to verify the predicted behavior, the optical setup is composed of a cw visible laser source whose beam is focused at the entrance faces of congruent undoped LiNbO3 samples
A probe at 1.06 m is efficiently confined (Fig. 8(c)) and even a 1.55 m wavelength beam can be properly guided (Fig. 8(d)). These results clearly demonstrate that ordinary polarized spatial solitons induce deeper waveguides than extraordinary polarized solitons in LiNbO3
Summary
Since the first observation of optical spatial solitons by Kerr in the late 1980s [1], spatial solitons have been studied in various nonlinear media [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. Optical nonlinear effects are essentially light polarization sensitive, which inspires vectorial analysis Some media, such as Kerr AlGaAs [18,19], show weak soliton polarization dependence while others, like liquid crystal [20,21] or photorefractive (PR) materials, possess features that enhance anisotropy. For photovoltaic screening solitons at the heart of this work, the electro-optic effect and the photovoltaic effect is a function of light polarization This motivates the present study where the case of a photovoltaic screening soliton in a LiNbO3 crystal is treated in the frame of a2 + 1͒D model. In this work we present the possibility of using ordinary polarization to create bright spatial solitons and efficient circular waveguides in LiNbO3. The presence of the space-charge field component perpendicular to the applied field, which is usually neglected for PR solitons, is shown to have an impact on beams for particular configurations
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