Directional control of narrow-band thermal emission from nanoantennas

We investigate the directional control of narrow-band perfect thermal emission using a nanoscale Yagi–Uda antenna. Although Yagi–Uda antennas were demonstrated to achieve directional control in the optical and radio frequency regimes, they have not been applied for thermal infrared emission. Here, by coupling a nanoscale thermal emitter into a Yagi–Uda antenna, we demonstrate strong directional control of thermal emission with a narrow-band spectrum at the nanoscale. By exploring the effects of the reflector and the director of a Yagi–Uda antenna, the forward emission enhancement factor up to 8.3 is achieved through geometry optimization.