Richard Zannoni

Terahertz detection in single wall carbon nanotubes

It is reported that terahertz radiation from 0.69to2.54THz has been sensitively detected in a device consisting of bundles of carbon nanotubes containing single wall metallic carbon nanotubes, quasioptically coupled through a lithographically fabricated antenna, and a silicon lens. The measured data are consistent with a bolometric detection process in the metallic tubes and the devices show promise for operation well above 4.2K.

Development of integrated HEB/MMIC receivers for near-range terahertz imaging

We present measurement results for a new type of integrated terahertz receiver, as an extension to previous work by the authors. The receiver we developed integrates quasi-optically coupled phonon-cooled NbN hot electron bolometric (HEB) mixers in close proximity with InP monolithic microwave integrated circuit (MMIC) intermediate-frequency (IF) amplifiers. We have measured antenna radiation pattern, receiver noise temperature, and bandwidth, as well as short-term stability of the integrated receivers. The measurements were performed at 1.6 and 2.5 THz over a very broadband IF frequency range. We have been able to extend the effective bandwidth of these receivers up to 5 GHz, the widest reported for any integrated configuration operating above 1 THz. The suitability of the HEB/MMIC approach for imaging applications has been confirmed through the development of a prototype system for near-range scanning. The results presented here are very promising for the future development of heterodyne focal plane arrays for space-based receivers, medical applications, and surveillance

Direct and heterodyne detection of microwaves in a metallic single wall carbon nanotube

This letter reports measurements of microwave (up to 4.5GHz) detection in metallic single walled carbon nanotubes. The measured voltage responsivity was found to be 114V∕W at 77K. The authors also demonstrated heterodyne detection at 1GHz. The detection mechanism can be explained based on standard microwave detector theory and the nonlinearity of the dc IV curve. The authors discuss the possible causes of this nonlinearity. While the frequency response is limited by circuit parasitics in this measurement, the authors discuss evidence that indicates that the effect is much faster and that applications of carbon nanotubes as terahertz detectors are feasible.

TREND: a low-noise terahertz receiver user instrument for AST/RO at the South Pole

Based on the excellent performance of NbN HEB mixer receivers at THz frequencies which we have established in the laboratory, we are building a Terahertz REceiver with NbN HEB Device (TREND) to be installed on the 1.7 meter diameter AST/RO submillimeter wave telescope at the Amundsen/Scott South Pole Station. TREND is scheduled for deployment during the austral summer season of 2002/2003. The frequency range of 1.25 THz to 1.5 THz was chosen in order to match the good windows for atmospheric transmission and interstellar spectral lines of special interest. The South Pole Station is the best available site for THz observations due to the very cold and dry atmosphere over this site. In this paper, we report on the design of this receiver. In particular, we report on HEB mixer device performance, the quasi-optical coupling design using an elliptical silicon lens and a twin-slot antenna, the laser local oscillator (LO), as well as the mixer block design and the plans for coupling the TREND receiver to the sky beam and to the laser LO at the AST/RO telescope site.

Microwave and terahertz detection in bundles of single-wall carbon nanotubes

We present new data on microwave detection in bundles of carbon nanotubes (CNTs). In particular, we derive a circuit model based on ANA measurements. We also demonstrate the first terahertz detection (up to 2.54 THz) in bundles of CNTs that were deposited through dielectrophoresis across the smallest gap in log-periodic antennas. Data are given that support the hypothesis that the detection process is bolometric at THz frequencies. Future extensions are planned that will employ suspended CNTs and explore heterodyne detection. Finally, we have performed unique ab initio simulations of CNTs with the aim of comparing these with the experimental data.

NbN hot-electron bolometer receivers and focal plane arrays for the terahertz range

The next generation of hot electron bolometric (HEB) mixer receivers for terahertz frequencies is under development. In order to improve sensitivity and integration time, terahertz focal plane arrays with HEB elements are required. We have designed, fabricated, and tested a three-element focal plane array with HEB devices. We implemented a quasi-optical power coupling scheme using three elliptical silicon lenses. Recently developed wideband (0.5 GHz to 12 GHz) MMIC low noise amplifiers were directly integrated with HEB devices in a single block. The array was tested using an FIR laser as the LO source and a side band generator as the signal source. This is the first heterodyne array for a frequency above 1 THz, and the suitability of HEB elements in a terahertz FPA has thus been demonstrated. This development is also geared toward investigating new architectures for much larger arrays utilizing HEB elements. Additional issues to be resolved include an improved antenna design for efficient LO injection, compact and low power IF amplifiers, and cryogenic optimization.