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

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

    Research output: Contribution to journalArticlepeer-review

    47 Citations (Scopus)

    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.

    Original languageEnglish
    Article number054113
    JournalPhysical Review B - Condensed Matter and Materials Physics
    Volume81
    Issue number5
    DOIs
    Publication statusPublished - 23 Feb 2010

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