NUMERICAL APPROACH TO CONTROL OF INFRARED OPTICAL PROPERTIES OF CONDUCTIVE OXIDE BY PERIODIC MICROSTRUCTURED GRATINGS

摘要

A manganese oxide, La_(1-x)Sr_xMnO_3, has attracted much attention because of its versatile changes of physical properties. It has the unique feature of large variation of the total hemispherical emittance ε_h depending on its temperature. Particularly, the ε_h of La_(0.825)Sr_(0.175)MnO_3 changes near room temperature accompanied by the metal-insulator transition. Variation in eH is greater than 0.40 for 173-373 K. However, the variation characteristics are determined by the molar ratio of Sr~(2+). Infrared optical properties of La_(0.825)Sr_(0.175)MnO_3 with periodic microstructured gratings are investigated to control the radiative properties and increase the ε_h variation. Numerical calculations based on rigorous coupled-wave analysis are performed for simulating the surface grating's infrared optical properties. A surface grating with simple rectangular cavities is investigated by varying the aperture size and cavity depth. Numerical calculations show that the periodic microstructured grating with simple rectangular cavities provides good spectral selectivity and increases the emittance. Calculation results show that the surface grating increases the amount of thermal radiation by 30 % and raises the ε_H variation.