Two-dimensional photonic crystal slabs in parallel-plate metal waveguides studied with terahertz time-domain spectroscopy

In this paper, we report our experimental study on two-dimensional photonic crystal slabs embedded inside parallel-plate metal waveguides, using terahertz time-domain spectroscopy. We observe that the temporal response of the photonic crystal slabs is significantly dispersed, indicative of strong dispersion near the edges of the photonic band gap. In the frequency domain, we observe several gaps whose sizes compare well with those from transfer matrix calculations. The group velocity and group velocity dispersion are characterized using a short-time Fourier transform analysis, and the results are consistent with the predictions from the photonic band structure. We have also measured reflection spectra using the photonic crystal as a 90◦ turning mirror, and in this way demonstrated frequency-selective components for quasi-optic guided wave propagation of terahertz pulses. (Some figures in this article are in colour only in the electronic version)