Implementation of radiative cooling with an inverse-designed selective emitter

The radiative cooling technology is a method of directly transmitting radiative energy to the cold sink of outer space through the existing atmospheric transparent window of 8-13 mu m. Therefore, it is necessary to find a selective emitter that can match the infrared atmospheric window. Here, we combine the selective emitter with the inverse design of the direct binary search (DBS) algorithm numerically. The periodic unit is glass photonics crystal (GPC) modified by DBS algorithm and a bottom layer of silver separated by a 11-mu m-thickness layer of glass. The simulation results reveal that the average emissivity of 8-13 mu m has been optimized from 71.8% to 94%. In addition, the proposed emitter remains a high reflectivity of 90.1% for the wavelength range from 1 mu m to 6 mu m in order to reduce the energy of absorption outside the transparent window. Both of the incident-angle insensitivity and polarization insensitivity are verified. With the above merits, the proposed emitter opens a novel approach to applications of radiative cooling based on inverse design.