Scheduling, Scaling Laws and Randomisation for Optimised Photopolymer Holographic Data Storage

摘要

The well known scaling law of holographic diffraction states that the replay diffraction efficiency η = ΠM~2, where M is the number of gratings (pages) stored, and Γ is a constant system parameter. This is an important metric used to quantify HDS material performance, and a great deal of experimental work to validate this rule for a wide variety of materials, (photorefractives, polymers etc.) have been presented over the years in the literature. No paper detailing the theoretical basis of this law, (i.e. including specific material characteristics, the recording geometry and/or the electromagnetic replay conditions), for photopolymers has previously been presented. In a recent paper [1] we have described in a clear way the optimization of the recording schedule in a photopolymer material governed by the Nonlocal Polymerization Driven Diffusion model (NPDD). One of the main assumptions made in [1] is that a long material relaxation time can be permitted between exposures. Another was that no phase shifts of the exposing pattern took place between exposures. In this paper we discuss these assumption and develop an intermediate first-order model. In a second paper [2], based on the results presented in [1] we have shown that our optimized predictions are in agreement with the scaling law of holographic diffraction. Thus the law is shown to hold for photopolymer recording media governed by the predictions of the NPDD. Based on our analysis: (ⅰ) A media inverse scaling law is proposed; (ⅱ) Γ is for the first time related to photopolymer material parameters and the hologram geometry and replay conditions; and (ⅲ) The form and validity of the diffraction efficiency inverse square scaling law for higher diffraction efficiency gratings is commented upon. In this paper we also review this result.