Contrast-reversible photorefractive incoherent-to-coherent optical converter by using an anisotropic strong volume hologram.
نویسندگان
چکیده
In the past several years photorefractive materials have been proposed for use as photorefractive incoherent-to-coherent optical converters (PICOC's) because of their dynamic real-time grating recording properties.'5 In a general PICOC, the imagebearing incoherent light is used to erase the grating, which is constructed by two coherent writing beams. The output image is carried by the diffracted beam from the grating, which can be produced by several methods including four-wave mixing," 2 anisotropic self-diffraction, 3 self-pumped phase conjugation,4 and grating projection.5 Because the incoherent erasure light is used to decrease the strength of the grating and then decrease the output intensity of the diffracted light, the output image is always a negative replica of the incoherent input image.'-4 In this Letter we demonstrate a new PICOC by using a strong volume hologram in which the erasure of the grating may let the output diffraction efficiency either increase or decrease. The contrast of the output image can be adjusted simply by controlling the writing conditions of the grating. In other words, this PICOC is contrast reversible. The diffraction properties of a volume hologram can be described accurately by the coupled-mode theory established by Kogelnik.6 The Bragg-matching diffraction efficiency for a volume transmission index grating is given by
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ورودعنوان ژورنال:
- Optics letters
دوره 18 8 شماره
صفحات -
تاریخ انتشار 1993