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Self-Focusing in Pulsed and Continuous Regime in Photorefractive Crystals KNbO3, LiNbO3, SrxBa1 xNb2O6

Photorefractive self-focusing and self-trapping has proved, over the past decade, to be an efficient low power method able to provide beam control and steering. In this paper, several photorefractive samples are investigated in the aim to provide a comparative study in both continuous wave and pulsed laser light regime. Whereas their holography-like behavior can be thought of as similar, they exhibit strong differences when considering the propagation of a single high contrast narrow beam. Perovskite KNbO3 and illmenite LiNbO3 are shown to exhibit respectively self-focusing and self-defocusing features, the latter needing an erasing process to be undertaken for the experiment to be fully reproducible. Finally, SrxBa1 xNb2O6 (SBN) is shown to be the most promising sample for applications ranging from optical limiting to all optical routing, though it exhibits instabilities such as optical branching.

Nicolas Fressengeas

@fresseng 11 yr. ago

Observation of the Light Beam Evolution in a Biased SBN Crystal in Pulsed and Continuous Regime

Photorefractive self-focusing and self-trapping has proved, over the past decade, to be an efficient low power method able to provide beam control and steering. Over the years, photorefractive SrxBa1 xNb2O6 has been shown to be the most promising photorefractive media in this field. Its ability to sustain photorefractive solitons at steady state has been thoroughly investigated. In this paper, the focus is set on the temporal development of self focusing in SrxBa1 xNb2O6, evidencing a soft transition from self-focusing through self-bending and finally optical-branching. This evolution is shown to occur not only as a function of experimental conditions such as electric field applied or beam intensity, but also as a function of time.

Nicolas Fressengeas

@fresseng 11 yr. ago

Observation of the light beam evolution in a biased SBN crystal in pulsed and continuous regime

Nicolas Fressengeas

@fresseng 11 yr. ago

Self-focusing in pulsed and continuous regime in photorefractive crystals: KNbO3, LiNbO3, SBN

Nicolas Fressengeas

@fresseng 11 yr. ago

Stabilization of the photorefractive double phase-conjugate mirror in BaTiO3

Photorefractive simple and double phase-conjugate mirrors very often exhibit strong instabilities in their reflectivities. One of their possible origins can be the competition between phase conjugation and its generating process, photorefractive beam fanning. However, by suitably choosing the incident beam widths and directions, we suppressed this competition and replaced it by the enhancement of each process by the other. This technique allows to obtain a double phase-conjugate mirror in BaTiO3 that establishes itself in seconds for beam intensities on the order of the tenth of a milliwatt. The reflectivities reached are on the order of 30% and stable within 3% for hours.

Nicolas Fressengeas

@fresseng 11 yr. ago

Simulation of the temporal behavior of one single laser pulse in a photorefractive medium

This paper presents a numerical modeling of the temporal evolution of the refraction index induced by a nanosecond single laser pulse propagating in a biased photorefractive crystal. Assuming particular hypotheses typical for a short pulse illumination, a nonlinear time dependent partial differential equation, which describes the mechanisms of space–charge field build up and evolution, is derived from a mono-dimensional Kukhtarev band transport model. The numerical resolution of this space–charge equation is then coupled to the simulation of the propagation of a beam in a nonlinear medium using a beam propagation method. The results evidence the spatial self-focusing of a single nanosecond laser pulse. A description of the output beam profile evolution during the laser pulse is obtained and the role of different physical parameters such as the carriers mobility and the fluence on self-focusing is investigated. A successful comparison to previous experimental measurements is reported.

Nicolas Fressengeas

@fresseng 11 yr. ago

Modelling and simulation of the growth of polymer micro-elements at the end of an optical fiber

Nicolas Fressengeas

@fresseng 11 yr. ago

Modélisation et simulation de la croissance de micro-éléments en extrémité de fibre optique

Nicolas Fressengeas

@fresseng 11 yr. ago

Photorefractive optical limiting

Nicolas Fressengeas

@fresseng 11 yr. ago

L'autofocalisation infrarouge dans le semi-conducteur InP:Fe

Nicolas Fressengeas

@fresseng 11 yr. ago

Modelling and simulation of the growth of polymer micro-elements at the end of an optical fiber

Nicolas Fressengeas

@fresseng 11 yr. ago

Model and simulation of the build-up of polymer micro-optical components on top of a fiber end

Nicolas Fressengeas

@fresseng 11 yr. ago

Photorefractive optical limiting

Nicolas Fressengeas

@fresseng 11 yr. ago

Photorefractive self-focusing in pulsed and continuous regime in SBN: application to Optical Limiting

Nicolas Fressengeas

@fresseng 11 yr. ago

Etude de l'autofocalisation transitoire dans le semiconducteur photoréfractif InP :Fe aux longueurs d'onde des télécommunications

Nicolas Fressengeas

@fresseng 11 yr. ago

Etude de l'auto-focalisation transitoire dans le semi-conducteur photoréfractif InP:Fe aux longueurs d'onde des télécommunications

Nicolas Fressengeas

@fresseng 11 yr. ago

Fast self-induced waveguides ine photorefractive semi-conductor InP:Fe for reconfigurable optical swiching

Nicolas Fressengeas

@fresseng 11 yr. ago

Time Resolved Applied Electric Field Masking in Photorefractive Semiconductors

We propose a theoretical analysis of the temporal self-focusing phenomena in the iron-doped indium phosphide (InP: Fe) semiconductor for low irradiations with continuous laser beams at infrared wavelengths for optical telecommunication applications such as optical switching and optical routing. Numerical models using two different methods based on charge transport equations are developed. The first method uses the classical finite differences scheme whereas the second method uses a novel algorithm based on Cellular Automata. Owing to the complexity of the non-linear differential system to be solved, full results are not retrieved but promising preliminary results are obtained and reviewed in this paper: they allow us to foresee that self-focusing on the millisecond time scale is possible in InP: Fe.

Nicolas Fressengeas

@fresseng 11 yr. ago

Spatio-temporal numerical resolution of Kukhtarev equation In InP:Fe photorefractif semiconductor

Nicolas Fressengeas

@fresseng 11 yr. ago

Theoretical and Experimental Temporal Self-Focusing Studies in Photorefractive InP:Fe at Telecommunication Wavelengths