An experimental study on the validity of diffraction theories for off-Bragg replay of volume holographic gratings

Abstract

We show that experiments clearly verify the assumptions made by the first-order two-wave coupling theory for one dimensional lossless unslanted planar volume holographic gratings using the beta-value method rather than Kogelnik's K-vector closure method. Apart from the fact that the diffraction process is elastic, a much more striking difference between the theories becomes apparent particularly in the direction of the diffracted beam in off-Bragg replay. We therefore monitored the direction of the diffracted beam as a function of the off-Bragg replay angle in two distinct cases:[a] the diffracted beam lies in the plane of incidence and [b] the sample surface normal, the grating vector and the incoming beam do not form a plane which calls for the vectorial theory and results in conical scattering.

Far-off-Bragg reconstruction of volume holographic gratings: A comparison of experiment and theories

“…6. The discrepancy to the value determined in the present work originates from three facts: (i) here we used experimentally measured values weighted by their standard error of the mean (no weighting in [27]), (ii) the angular range was extended to the far-off-Bragg region which has particular influence on the obtained thickness via the phase function through its minima, and (iii) the background was thoroughly subtracted. Browsing through the literature of evaluating the refractive-index modulation of volume holographic gratings, we find mainly two approaches: a) measuring a rocking curve and calculating n 1 and d by using the KVCM in the linearized version and b) just assuming the grating thickness to be the measured mechanical sample thickness and calculating n 1 from the diffraction efficiency at the (supposed to be) Bragg angle.…”

“…The sample is the same as used for the experiments concerning the direction of the diffracted beam discussed in Ref. [27]. A schematic of the setup is shown in Fig.…”

Holographic Gratings for Slow-Neutron Optics

“…Still, at this stage of development of holographic gratings, one can observe small vertical deflections as predicted from phase matching conditions at the grating surface that naturally arise from certain assumptions in diffraction theories. Such deflections have recently been studied with light [75] and are still to be observed for matter waves. The expected deviation angles are of the order of $\Delta \zeta \approx {10}^{-5}$ rad for $\lambda =10$ nm.…”

A Review of the Optimisation of Photopolymer Materials for Holographic Data Storage

“…Using this method, high peak reflectivity of 83% was achieved and reached for a neutron wavelength of 3.76 nm. Such results, besides extending the range of passive neutron optical elements available, have also provided evidence for the superiority of the Betavalue method over Kogelnik's K-vector closure method [89,90].…”