Terahertz Carrier Research Articles

Gigahertz modulation of tunable terahertz radiation from photomixers driven at telecom wavelengths

Here, we report the gigahertz-rate modulation of a tunable terahertz carrier. Terahertz radiation, tunable from 300 GHz to 1.2 THz, is generated by mixing two telecom lasers with an offset frequency in an ultrafast In0.53Ga0.47As photoconductive device coupled to a broadband antenna. The microwave modulation applied to the telecom lasers is directly transferred to the terahertz carrier. A maximum modulation rate of 20 GHz has been achieved, and the bandwidth is independent of the carrier frequency.

Coherent control of terahertz emission and carrier populations in semiconductor heterostructures

A short laser pulse exciting semiconductor heterostructures will induce a time-varying polarization that in turn leads to the generation of terahertz radiation. Although there are several possible mechanisms for this time-dependent polarization, some depend critically on the dephasing time of the photoexcited carriers. For long dephasing times it is possible to control both the populations and the coherence of these particles by proper shaping of the optical pulse. We discuss our recent experimental and theoretical work on coherent terahertz radiation emitted from semiconductor heterostructures when the exciting optical fields are shaped in both amplitude and phase. Our shaping techniques include phase-locked pulse generation in a Michelson interferometer and pulse-train generation by phase-only filtering.