We report reliability-test results of transmission-type holographic optical elements (HOE's) made with the DuPont photopolymer HRF-600. The reliability tests performed include 6000 cycles of liquid-to-liquid thermal-shock cycling (-55 degrees C-125 degrees C), 2200 cycles of air-to-air thermal cycling (-55 degrees C-125 degrees C), 1500 h of humidity testing (85 degrees C and a relative humidity of 85%), and 675 h of burn-in testing at 125 degrees C. A total of 210 holograms was tested, with 532 data points collected for diffraction-efficiency measurements. The results show that the average efficiency change after these tests is in the range of -4% to 0% and the standard deviation is only ~10%.

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This paper discusses material behaviors of holographic materials in terms of mechanical, thermomechanical properties and their effects on optical efficiency. Experiments were carried out to characterize coefficient of thermal expansion, stress strain curves, and dynamic mechanical behaviors of photopolymers. It has been found that in-plane deformation of photopolymer has a minimum effect on the diffraction efficiency while out-of-plane deformation can significantly contribute to the diffraction efficiency of holographic optical elements.

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