Researchers at Sandia National Laboratories and the University of New Mexico (both in Albuquerque, NM) have numerically optimized tungsten photonic-crystal (PC) thermal emitters for certain IR bands and simulated how they emit in comparison to an ideal blackbody emitters in the same bands. They found that the PC emitters emitted mostly in a narrow-angle forward-emission profile, and at an emitter efficiency more than twice that of the ideal blackbody emitters. When integrated across the desired wavelength band, the PC was from 65% to 75% more power efficient than the blackbody.

They chose a commonly tested PC design: a 3-D “Lincoln Log” structure of tungsten. After a so-called genetic optimization of an eight-layer PC based on rigorous coupled-wave analysis, the PC was analyzed assuming it received its heat conductively from an ideal blackbody source. Versions of the PC were optimized and analyzed for the 3 to 5, 5 to 7, 7 to 9, and 9 to 11 µm IR bands. The resulting PC emitters could greatly boost the efficiency of thermal photovoltaic cells for energy generation, and also provide a good way to test thermal sensors and seekers. Contact Ihab El-Kady at ielkady@sandia.gov.