Spectral control of THz thermal radiation using an electromagnetic crystal

Terahertz (THz) frequency radiation has many spectroscopic and imaging applications. Because it suffers from a limited propagation distance in air due to strong water absorption and a historic lack of inexpensive sources, radiation in the THz frequency range has not been commercialized to its fullest extent [1]. Thermal generation of THz radiation is one common source, even though THz frequencies are well below the room temperature thermal emission maximum. We are exploring the degree to which we can control the spectral emission of a heated source in the THz frequency range using electromagnetic band gap or electromagnetic crystal structures. In particular, we are experimentally investigating a simple 1D, bilayered electromagnetic crystal structure composed of air and silicon slabs. Thermal radiation from electromagnetic crystals has been studied experimentally for higher frequency ranges [2], as well as theoretically, but often only for infinite lattices [3], [4], [5]. It has even been claimed to have measured output powers larger than the corresponding blackbody levels, although this is still controversial [6], [7]. Our ultimate goal is to be able to control the spectral emission of an electromagnetic crystal in the THz region by engineering its band structure. Controlled thermal emission could be used for applications as diverse as solar energy [8].