5 November 2014 Effect of environmental temperature on diffraction efficiency for multilayer diffractive optical elements in Mid-wave infrared
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In this paper, the effect of environmental temperature change on multilayer diffractive optical elements (MLDOEs) is evaluated from the viewpoint of the diffraction efficiency and the polychromatic integral diffraction efficiency (PIDE). As environmental temperature changes, the microstructure heights of MLDOEs expand or contract, and refractive indices of substrate materials also change. Based on the changes in microstructure height and substrate material index with environmental temperature, the theoretical relation between diffraction efficiency of MLDOEs and environmental temperature is deduced. A practical 3-5μm Mid-wave infrared (MWIR) optical system designed with a MLDOE, which made of ZNSE and GE, is discussed to illustrate the influence of environmental temperature change. The result shows that diffraction efficiency reduction is no more than 85% and PIDE reduction is less than 50% when environmental temperature ranges from -20°C to 60°C. According to the calculated diffraction efficiency in different environmental temperatures, the MTF of hybrid optical system is modified and the modified MTF curve is compared with the original MTF curve. Although the hybrid optical system achieved passive athermalization in above environmental temperature range, the modified MTF curve also remarkably decline in environmental temperature extremes after the consideration of diffraction efficiency change of MLDOE. It is indicated that the image quality of hybrid optical system with ZNSE-GE MLDOE is significantly sensitive to environmental temperature change. The analysis result can be used for optical engineering design with MLDOEs in MWIR.
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Mingxu Piao, Mingxu Piao, Qingfeng Cui, Qingfeng Cui, Hao Zhu, Hao Zhu, Bo Zhang, Bo Zhang, "Effect of environmental temperature on diffraction efficiency for multilayer diffractive optical elements in Mid-wave infrared", Proc. SPIE 9272, Optical Design and Testing VI, 927217 (5 November 2014); doi: 10.1117/12.2071245; https://doi.org/10.1117/12.2071245

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