Now, Ziwei Fan and colleagues, from the USA and China, have demonstrated directional thermal emission using pixelated, large-area, micro-optical arrays (Z. Fan et al. Nat. Commun. 15, 4533; 2024). Using carefully designed micro-optics (top left picture), the team experimentally demonstrated broadband, polarization-independent directional control of thermal radiation. The directional micro-emitter was used to enable a pixelated infrared display (top right and bottom pictures). It is hoped that the findings may have implications for radiative cooling, infrared spectroscopy, thermophotovoltaics, and thermal camouflaging.

The corresponding author on the manuscript, Zi Jing Wong, told Nature Photonics that “their approach leveraged etendue conservation to redirect isotropically emitting thermal radiation into a narrow angular range…By creating three-dimensional hexagonal pixel structures composed of oppositely facing parabolic reflectors, we successfully attained polarization-independent and highly directional thermal emission over an extremely wide spectral range.”