Density grating diffusive

Figure 17. Schematic cross sections of a photopolymer material in which a grating pattern is being written, (a) The image exposure forms polymer and depletes the monomer concentration, (b) Additional monomer diffuses into the exposed areas, (c) An overall development exposure completes the polymerization to give a polymer with a modulated density.

Although, the transient grating measurements yield values for thermal diffusivity for each IL directly, the thermal conductivity must be found from a knowledge of the density and specific heat capacity through the relation a = Only a few values of density and heat capacity have... 

In a practical sense, the studies of Ostermayer et al. allow selection of material properties which favor high grating resolution. The reaction velocity Is a dominant effect, and rapid dissolution of oxidation products is necessary. Furthermore, a low lateral diffusion of surface holes is fostered by high doping density and low D. If doping densities are too high, however, then anodic dark currents may become problematic. 

Figure 9.6. Interference of the propagative index gratings (arising from electrostrictive density changes) with the diffusive 9 (but not propagative) thermal grating.

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