Dual-band quasi-coherent radiative thermal source

Thermal radiation from an unpatterned object is similar to that of a gray body. The thermal emission is insensitive to polarization, shows only Lambertian angular dependence, and is well modeled as the product of the blackbody distribution and a scalar emissivity over large frequency bands. Here, we design, fabricate and experimentally characterize the spectral, polarization, angular and temperature dependence of a microstructured SiC dual band thermal infrared source; achieving independent control of the frequency and polarization of thermal radiation in two spectral bands. The measured emission of the device in the Reststrahlen band (10.3-12.7 µm) selectively approaches that of a blackbody, peaking at an emissivity of 0.85 at λx=11.75μm and 0.81 at λy=12.25μm. This effect arises due to the thermally excited phonon polaritons in silicon carbide. The control of thermal emission properties exhibited by the design is well suited for applications requiring infrared sources, gas or temperature sensors and nanoscale heat transfer. Our work paves the way for future silicon carbide based thermal metasurfaces.