Terahertz photonics: ultrafast physics and applications

We present theoretical and experimental results for the generation of both transmission-line-coupled terahertz electrical transients and free-space terahertz radiation. Time-resolved reflectivity experiments are used to gain insight into the ultrafast carrier dynamics and fundamental limitations of conventional photoconductive (PC) switches. Self-switching and frozen wave generation are introduced as effective sources of terahertz electrical transients, and the PC response of these techniques is seen to be independent of the charge carrier lifetime in the semiconductor substrate. The concept of PC switching is further extended to the launching of free-space terahertz radiation, and electro-optic sampling techniques using polycrystalline sensors are shown to be viable sensors for free-space terahertz radiation.