Mode-selective thermal radiation from a microparticle

We experimentally demonstrate that thermal radiation from a micron-sized dielectric particle depends sensitively on its size and shape through the cavity quantum-electrodynamic effect. Our laser trapping technique levitated a high-temperature microsphere of Al2O3 and enabled emission spectroscopy of the single particle. As the particle becomes smaller, a blackbodylike spectrum turns into a spectrum dominated by multiple peaks resonant with whispering gallery modes of the spherical resonator. The observed sharp frequency selectivity is applicable to spectral control of thermal radiation.