THz Thermal Emission Control Via Electromagnetic Band Engineering

In the following, we report on the design and implementation of an inexpensive thermal source for THz radiation with a highly tunable radiation signature. It consists of five 350- μm-thick Si wafers, each spaced 1 mm apart. The thermal emission of this structure was calculated analytically and numerically. A comprehensive study was performed that included analyzing the oblique incidence, polarization, and design tolerance effects. The thermal emission was calculated using both Kirchhoff´s law and directly using a Green´s function method. It was measured using a Michelson interferometer. The predicted and measured thermal emission spectra had peaks around 150 GHz apart, with a narrow bandwidth of 50 GHz. The peaks were up to 80% of the expected blackbody levels and the bandgaps had emission levels of about 20% of those blackbody values. We demonstrate that, using these techniques, it is possible to achieve a desired THz thermal emission signature, with narrowband features that can be engineered to have specific angles of emission and polarization states.