Exploring novel terahertz detectors and sources with the UCSB free-electron lasers.

Summary form only given. The UCSB free-electron lasers energize two research thrusts - terahertz resonant detectors, and terahertz Bloch oscillators. Work on terahertz resonant detectors focuses on plasmonic resonances in grating gated field effect transistors. The resonant response, ~ 50 GHz wide, can be tuned with gate voltage and grating geometry. Gating a narrow region of the channel to threshold enhances reponsivity. The pinched off region develops a barrier to electron flow and "Schottky like" characteristics, exhibiting strong bolometric or rectified response with time constants varying from submicroseconds to 10\´s of microseconds. Efforts to make a Bloch oscillator oscillate use super- superlattices comprised of short period superlattices interleaved by heavily doped n+ regions. Room temperature terahertz photon assisted transport, excited by the radiation from the FEL\´s, supports the notion that the super-superlattice structure supports uniform Stark ladders when subjected to sufficiently strong electric fields to bring matwerialthe super- superlattice into the Bloch oscillator limit. Current work fabricates metal clad ring resonators and pulse excites them with ~ microsecond long pulses or -microsecond long bursts of intense 9GHz radiation.