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Title

Modification of refractive index by a single femtosecond pulse confined inside a bulk of a photorefractive crystal

Author(s)

Gamaly, Eugene G.;  Juodkazis, Saulius;  Mizeikis, Vygantas;  Misawa, Hiroaki;  Rode, Andrei V.;  Krolikowski, Wieslaw

Abstract

We demonstrate that the interaction of intense femtosecond pulse with photorefractive crystal at conditions close to the optical-breakdown threshold differs drastically from that of long pulse and cw illumination. Our theoretical estimations show that the high number density of excited electrons modifies the dielectric function leading to the transient negative change in the refractive index, Δn/n0∼−10−2 that vanishes on nanosecond time scale. Moreover, the high-frequency laser field, two orders of magnitude larger than the field of spontaneous polarization, prevents the stationary charge distribution during the pulse. The diffusion and recombination of charge carriers continues over a nanosecond time scale, after the end of the pulse. The main driving force for the current after the pulse is the field of spontaneous polarization in the ferroelectric medium: the current terminates when the field of charge separation balances this field. We show here that the stationary modification of refractive index according to this model is then independent of the polarization of the pump light beam, in agreement with experiments, and saturates at Δn≈10−3 in semiquantitative fit to the experimental data.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Engineering and Industrial Sciences. Centre for Micro-Photonics

Source

Physical Review B, Vol. 81, no. 5 (Feb 2010)

Publication year

2010

FOR Code(s)

01 Mathematical Sciences;  02 Physical Sciences;  09 Engineering

Keyword(s)

Femtosecond pulses;  Photorefractive crystals;  Spontaneous polarization

Publisher

American Physical Society

ISSN

1098-0121

Publisher URL

http://dx.doi.org/10.1103/PhysRevB.81.054113

Copyright

Copyright © 2010 The American Physical Society. Published version of the paper reproduced here with the kind permission of the publisher for non-commercial purposes only.

Full text

Peer reviewed