A quantitative measurement for the photorefractive index modulation of reflection gratings in LiNbO3

Photorefractive crystals, in particular LiNbO3, can be used for the storage of optical information. The storage capacity is related to the photorefractive index modulation of grating, Deltan. This article is the first to report the use of wavelength detuning to measure the Deltan for the reflection type of grating. The method involves extracting the half-width Deltalambda(1/2) from the wavelength scan of the diffraction efficiency for a reflection grating and using an experimental correlation between Deltalambda(1/2) and Deltan derived in this article to calculate the photorefractive index modulation, Deltan. The half-width Deltalambda(1/2) of 0.14 Angstrom is the narrowest selectivity reported thus far (attained by using a narrow band laser source), and allows us to deduce the Deltan of this reflection grating as 3.7 x 10(-5) using the above correlation. (C) 2004 Elsevier B.V. All rights reserved.