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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Oscillating holograms recorded in photorefractive crystals by a frequency detuned feedback loop

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Author(s):
Freschi, A. A. [1] ; Telles, A. C. C. [2] ; Frejlich, J. [3] ; Donatti, D. A. [1]
Total Authors: 4
Affiliation:
[1] Univ Estadual Paulista, Dept Fis, IGCE, BR-13500970 Sao Paulo - Brazil
[2] CenPRA, BR-1306901 Campinas, SP - Brazil
[3] Univ Estadual Campinas, IFGW, Lab Opt, BR-13083970 Campinas, SP - Brazil
Total Affiliations: 3
Document type: Journal article
Source: Journal of Applied Physics; v. 105, n. 2 2009.
Field of knowledge: Physical Sciences and Mathematics - Physics
Web of Science Citations: 2
Abstract

We report an optoelectronic feedback loop suitable for generating noise-free interference patterns oscillating at arbitrary waveforms. The technique allows controlling the frequency detuning between the interfering beams through a phase modulator in a closed-loop interferometer. We use the dither signal method and propose a quasisynchronous demodulation scheme to create a phase modulated error signal for driving the loop. The dynamics of the interference fringes is easily controlled by a voltage waveform from a function generator, which is used in association with a time delay circuit for shifting the frequency of the reference signal used for lock-in demodulation. The technique is specially suited for applications involving low-frequency phase oscillations, such as those frequently encountered in the generation of space-charge waves in highly resistive photorefractive materials. The processing scheme allows real time monitoring of the hologram strength, and absolute values for the diffraction efficiency and the holographic phase shift can be obtained. Photorefractive wave oscillations ranging from approximately 100 mHz to 10 Hz were produced in a nominally undoped Bi12TiO20 sample. The technique can be readily applied to other fields of optical interferometry, such as for testing optical surfaces, optimizing adaptive holographic devices, measuring physical quantities, among other applications. (AU)

FAPESP's process: 03/09915-0 - Photosensitive materials
Grantee:Jaime Frejlich
Support Opportunities: PRONEX Research - Thematic Grants