Thermal emission of midinfrared GaAs photonic crystals

We have investigated the thermal emission of midinfrared dielectric photonic crystals. We show that the optical properties of the photonic crystals can be probed by the photomodulation of the room-temperature thermal emission. The technique is illustrated in the case of membrane-type two-dimensional photonic crystals. The GaAs-based photonic crystal membranes were fabricated by wafer bonding followed by standard e-beam lithography and etching processes. Thermal radiation collected from the surface of the sample allows one to investigate experimentally a broad spectral range from 500 to $1500{\text{cm}}^{-1}$. Zone-center modes at the $\Gamma$ point coupled to the radiative continuum are evidenced around $900{\text{cm}}^{-1}$ ($11\mu \text{m}$ wavelength). The lattice periodicity of the photonic crystals allows one to spectrally tailor the emissivity. Three-dimensional finite-difference time-domain modeling is used to explain the thermal radiation spectra of the photonic crystal characterized by optical sources embedded in the whole structure.