Photopolymer material for holography.
An experimental Du Pont holographic photopolymer material produces an index modulation in excess of 10(-2) utilizing a diffusion mechanism. Optimum exposure in air is typically 30 mJ/cm(2) , in nitrogen 3 mJ/cm(2). Composition, beam ratio, and exposure power all affect the index modulation. This, combined with thickness variations, permits diffraction efficiency to be preadjusted for a variety of desired angular responses and spatial frequencies. The material can be easily overmodulated according to Kogelnik's phase grating theory. No wet processing is required. After total polymerization, storage at 100 degrees C, -60 degrees C, and under water does not significantly affect the diffraction efficiency. Image-object superposition is exact for real-time holography. Excellent copies of silver halide holograms with four times the original efficiency have been made. Grating devices with tailored peak or flat wavelength response can be constructed.
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