Narrow Results

Experimental measurements of photoresistivity under terahertz (THz) radiation in low magnetic fields at conditions of cyclotron resonance (CR) in two-dimensional electron system (2DES) of GaAs/AlGaAs nanostructures are presented and discussed. We report the experimental discovery of “CR-vanishing effect” (CRV) in GaAs/AlGaAs heterostructures with high mobility as a well-defined gap on CR-line that is independent on incident THz power. Our analysis shows that the CRV may appear in systems with well correlated state of 2D electrons such as plasma waves and others. Fundamental nature of these correlated states of electrons in 2DES is discussed. Future THz detectors utilizing the new correlated states in 2DES may expand horizons for supersensitive detection in sub-THz and THz frequencies ranges.

We report our development of terahertz (THz) quantum-cascade lasers with record performance. Using those high-power lasers as the illumination sources and a focal-plane array camera, we are able to perform real-time THz imaging at video rate.

Terahertz time-domain measurements using air as the emission and detection medium are shown to enable broadband spectroscopy with continuous coverage of the entire terahertz band, from 0.1 to over 10 THz. It is shown that the unique properties of using a gaseous medium allow for excellent phase matching without interruptions from crystalline phonon modes or antenna resonant structures from conventional solid state emitters and sensors, allowing the full bandwidth of the laser pulse to be used. It is also shown that the limiting factor on the system bandwidth is the temporal profile of the probe pulse used for detection, and how modification of this profile can further enhance the detection bandwidth.