Enhancement of spectrally controlled near-field radiation transfer by magnetic polariton generated by metal-insulator-metal structures

Near-field radiation transfer between a metal-insulator-metal (MIM)-structured emitter and receiver was investigated through numerical simulation using a finite difference time domain (FDTD) method. Both the emitter and receiver consist of a squared-island-type metal array composed of nickel (Ni), an insulator layer composed of silicon dioxide (SiO2), and a metal substrate composed of nickel (Ni). The emitter and receiver were set up with a vacuum gap of a few hundred nanometers. The results showed that the near-field radiation flux was enhanced by a factor of approximately four, when compared to that between blackbody surfaces. Simultaneously, the enhancement was spectrally controlled over frequencies ranging from 9 x 10(14) to 20 x 10(14) rad/s (approximating to a wavelength range of 0.9 to 2.1 mu m) depending on the size of the squared island. Images of the magnetic field in both the emitter and receiver clarified that the spectrally enhanced radiation flux was caused by the magnetic polariton (MP)) generated in the insulator between the squared-island metal and the substrate metal when the frequency of the MP coincided with that of the near-field radiation. Moreover, the resonance mode between the frequencies of the MP and near-field radiation was predicted by an impedance model that considered the capacitance between the islands in the emitter and receiver, in addition to the conventional circuit of a MIM structure.