Lawrence, Justin R.
Lawrence, Justin R.
Lawrence, Justin R.
Now showing 1 - 4 of 4
- PublicationComparison of holographic photopolymer materials by use of analytic nonlocal diffusion models(Optical Society of America, 2002-02-01)
; ;The one-dimensional diffusion equation governing holographic grating formation in photopolymers, which includes both nonlocal material response and generalized dependence of the rate of polymerization on the illuminating intensity, has been previously solved under the two-harmonic expansion assumption. The resulting analytic expressions for the monomer and polymer concentrations have been derived and their ranges of validity tested in comparison with the more accurate numerical four-harmonic case. We used these analytic expressions to carry out a study of experimental results presented in the literature over a 30-year period. Automatic ﬁtting of the data with these formulas allows material parameters, including the nonlocal chain-length variance σ, to be estimated. In this way, (i) a quantitative comparison of different materials can be made, and (ii) a standard form of experimental result presentation is proposed to facilitate such a procedure. 370Scopus© Citations 58
- PublicationAdjusted intensity nonlocal diffusion model of photopolymer grating formation(Optical Society of America, 2002-04-01)
; ;Diffusion-based models of grating formation in photopolymers have been proposed in which the rate of monomer polymerization (removal) is directly proportional to the illuminating intensity inside the medium. However, based on photochemical considerations, the rate of polymerization is proportional in the steady state to the square root of the interference intensity. Recently it was shown that, by introducing a nonlocal response function into the one-dimensional diffusion equation that governs holographic grating formation in photopolymers, one can deduce both high-frequency and low-frequency cutoffs in the spatial-frequency response of photopolymer materials. Here the ﬁrst-order nonlocal coupled diffusion equations are derived for the case of a general relationship between the rate of polymerization and the exposing intensity. Assuming a twoharmonic monomer expansion, the resultant analytic solutions are then used to ﬁt experimental growth curves for gratings fabricated with different spatial frequencies. Various material parameters, including monomer diffusion constant D and nonlocal variance s, are estimated. 389Scopus© Citations 89
- PublicationThickness variation of self-processing acrylamide-based photopolymer and reflection holography(Society of Photo-Optical Instrumentation Engineers, 2001-04)
; ;There are many types of holographic recording material. The acrylamide-based recording material examined here has one significant advantage: it is self-processing. This simplifies the recording process and enables holographic interferometry to be carried out without the need for complex realignment procedures. However, the effect that the polymerization process has on the grating thickness must be examined. This question is fundamental to the material’s use in holographic optical elements, as thickness variations affect the replay conditions of the produced elements. This paper presents a study of this thickness variation and reports for the ﬁrst time the production of reﬂection holographic gratings in this material. 487Scopus© Citations 45
- PublicationNonlocal-response diffusion model of holographic recording in photopolymer(Optical Society of America, 2000-06-01)
;The standard one-dimensional diffusion equation is extended to include nonlocal temporal and spatial medium responses. How such nonlocal effects arise in a photopolymer is discussed. It is argued that assuming rapid polymer chain growth, any nonlocal temporal response can be dealt with so that the response can be completely understood in terms of a steady-state nonlocal spatial response. The resulting nonlocal diffusion equation is then solved numerically, in low-harmonic approximation, to describe grating formation. The effects of the diffusion rate, the rate of polymerization, and a new parameter, the nonlocal response length, are examined by using the predictions of the model. By applying the two-wave coupled-wave model, assuming a linear relationship between polymerized concentration and index modulation, the resulting variation of the grating diffraction efficiency is examined. 490Scopus© Citations 245