Frequency and amplitude stabilized terahertz quantum cascade laser as local oscillator

We demonstrate an experimental scheme to simultaneously stabilize the frequency and amplitude of a 3.5 THz third-order distributed feedback quantum cascade laser as a local oscillator. The frequency stabilization has been realized using a methanol absorption line, a power detector, and a proportional-integral-derivative (PID) loop. The amplitude...

Noise temperature and beam pattern of an NbN hot electron bolometer mixer at 5.25 THz

We report the measured sensitivities of a superconducting NbN hot electron bolometer (HEB) heterodyne receiver at 5.25 THz. Terahertz (THz) radiation is quasioptically coupled to a HEB mixer with a lens and a spiral antenna. Using a measurement setup with black body calibration sources and a beam splitter in vacuo, and an antireflection coated...

IF impedance and mixer gain of NbN hot electron bolometers

The intermediate frequency (IF) characteristics, the frequency dependent IF impedance, and the mixer conversion gain of a small area hot electron bolometer (HEB) have been measured and modeled. The device used is a twin slot antenna coupled NbN HEB mixer with a bridge area of 1×0.15??m2, and a critical temperature of 8.3?K. In the experiment the...

Current-induced vortex unbinding in bolometer mixers

We present a description of the current-voltage characteristics of hot electron bolometers in terms of the current-dependent intrinsic resistive transition of NbN films. We find that, by including this current dependence, we can correctly predict the complete current-voltage characteristics, showing excellent agreement with measurements for both...

Terahertz heterodyne receiver based on a quantum cascade laser and a superconducting bolometer

We report the first demonstration of an all solid-state heterodyne receiver that can be used for high-resolution spectroscopy above 2?THz suitable for space-based observatories. The receiver uses a NbN superconducting hot-electron bolometer as mixer and a quantum cascade laser operating at 2.8?THz as local oscillator. We measure a double...

Doubling of sensitivity and bandwidth in phonon cooled hot electron bolometer mixers

We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. We show experimentally that both the receiver noise temperature and the gain bandwidth can be improved by more than a factor of 2 by cleaning the interface and adding...