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

Autor(es)

Freschi, A. A. ^[1] ; Telles, A. C. C. ^[2] ; Frejlich, J. ^[3] ; Donatti, D. A. ^[1]

Afiliação do(s) autor(es)

^[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

• Tipo de documento: Artigo Científico
• Fonte: Journal of Applied Physics; v. 105, n. 2 2009.
• Área do conhecimento: Ciências Exatas e da Terra - Física
• Citações Web of Science: 2
• Assunto(s): Óptica eletrônica Interferência da luz Interferometria

Resumo

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)

• Processo FAPESP: 03/09915-0 - Materiais fotossensíveis
• Beneficiário: Jaime Frejlich
• Modalidade de apoio: Auxílio à Pesquisa - Programa PRONEX - Temático