Optimization of photonic crystal interfaces for high efficiency coupling of terahertz waves

We present an efficient method to couple terahertz waves from a dielectric medium into a two-dimensional photonic crystal. The design parameters of the photonic crystal interface to minimize reflection can be optimized using the conventional antireflection coating theory and the finite-difference time-domain simulations. We investigate the transmission spectra of a terahertz photonic crystal with and without the optimization of the crystal interface. It is shown that the transmission of the specific terahertz wave of interest can be significantly improved through the optimization of the photonic crystal interface.