THz detection with SUperconducting Nanodevices – T SUN

The THz region of the electromagnetic spectrum, which may be defined as covering the range from 0.3 to 10 THz is a frontier area for research in many fields, including physics, astronomy, chemistry, material science, communication, biology and medicine. Indeed, THz radiation can propagate through light materials and within the atmosphere for specific frequency windows, enabling imaging at a distance in situations where regular optical systems cannot, that is through fog, tissues, clothes, walls. Since their frequency is very high, THz waves can be used for large data rate communications. Moreover, since most materials have specific rotational or vibrational modes in this wavelength region, spectroscopy using THz is a powerful tool to identify substances, such as pollutants, chemicals, explosives, odd biological samples. Combined with the capability to "see through", it is possible to make "hyperspectral" imaging of a hidden scene. However, despite the tremendous array of possible applications, the THz region of the electromagnetic spectrum has, so far, not been exploited fully due to the limited number of suitable sources and detectors. Although a wide range of technology has recently begun to fill the THz gap, there are still needs of high sensitivity and high resolution detectors, with low power consumption, that can be fitted in a small volume. High Tc Superconductors (HTSc) devices are good candidates, which can operate at high frequency (a few THz) and at rather high temperature (77 K) that can be reached easily with a simple and compact cryocooler.
In collaboration with the LPN-Marcoussis, our team at LPEM-ESPCI has developed a powerful technique to structured HTSc thin films at the nanometer scale, combining advanced electronic lithography technique with ion irradiation technique. In particular we have been able to produce reliable and reproducible superconducting nanosize Josephson Junctions (JJ), which are the main active components of superconductive electronics to build THz mixers, integrated THz local oscillators, analog-to-digital converters, digital circuits, or SQUID-based magnetometers and gradiometers, as the main examples.
The aim of this project is to focus on the development of all the essential superconducting blocks to build a heterodyne spectroscopic receiver operating above 30 K in the frequency range of 0.3-3THz, where it is possible to detect concealed objects, to do drug spectroscopy and more generally to perform passive sensing for security, environment, radio-astronomy. The device will integrate on the same chip a receiver (Josephson junction) coupled to a tunable local oscillator (Josephson junction arrays) and will be made using the irradiation technology.
Moreover, the realization of an integrated local oscillator (LO) tunable in a wide band of frequency is an important output of our project. Such device can also be used as reference clock for JJ-based Rapid Single Flux Quantum (RSFQ) circuits for digital processing. Indeed, the technology proposed for this project allows, in the long term, to build THz imagers for which high data rate digital processing of the output signals can be performed on-chip with RSFQ digital electronics. A tunable LO is also suitable for other applications in the GHz range (1-20 GHz), for radar or software-defined radio-receivers applications. By using the beating between two high frequency signals generated by our LOs, we can make highly tunable oscillators in the frequency range of interest.
The work is organized in 6 workpackages : (1) Management (2) Detection with external LO (3) Detection with tunable on-chip LO (4) Spectroscopy and Imaging (5) Nanofabrication (LPN/LPEM) (6) Dissemination.
The partners will collaborate to achieve their goal : a demonstrator of a fully integrator THz spectroscopic imager (beyond 300 GHz, and possibly up to 3 THz), working beyond 30 K, with a spectral resolution of a few MHz and a noise temperature below 1000K.