Integrated Submm Wave Spectrometer
Development of Integrated Submm Circuit Technology for Atmosphere Monitoring, Radio Astronomy and Security Survey
Tech Area / Field
- ENV-MIN/Monitoring and Instrumentation/Environment
- INS-DET/Detection Devices/Instrumentation
- PHY-RAW/Radiofrequency Waves/Physics
- PHY-SSP/Solid State Physics/Physics
3 Approved without Funding
Russian Academy of Sciences / Institute of Radioengineering and Electronics, Russia, Moscow
- Institute of Physics of Microstructures, Russia, N. Novgorod reg., N. Novgorod
- European Southern Observatory, Germany, Garching bei Müchen\nIstituto di Cibernetica del CNR, Italy, Pozzuoli\nHypres, USA, NY, Elmsford\nKarlsruhe University / Physikalisches Institut, Germany, Karlsruhe\nTechnical University of Denmark, Denmark, Copenhagen\nChalmers University of Technology, Sweden, Göteborg\nSpace Research Organization Netherlands, The Netherlands, Utrecht
Project summaryThe main objective of the project is the development and study of the submm wave integrated receivers with low noise level (limited only by quantum effects) and ultimate spectral resolution. Implementation of the nanotechnology techniques and integration of the separate elements in one microcircuit pe us an opportunity to develop compact spectrometer with ultimate (quantum) sensitivity and unique parameters, which can’t be realized on the base of traditional approaches and technologies. As a result of the project realization the onboard integrated spectrometers for Earth atmosphere monitoring, radio astronomy and security survey (frequency range 300 – 700 GHz, noise temperature 150 – 200 K) will be developed. The proposed project is intended for fundamental research activities that will improve understanding of fundamental processes in superconducting nanostructures; on the base of these fundamental results the practical devices with unique characteristics will be realized. Such devices are vitally required for practical applications of great importance: global security, environmental technologies, radio astronomy, Earth atmosphere monitoring, and medical diagnostic.
A Superconducting Integrated Receiver (SIR) was proposed by project participants more than 10 years ago. A SIR comprises in one chip (size of 4 mm*4 mm*0.5 mm) a low-noise Superconductor-Insulator-Superconductor (SIS) mixer with quasioptical antenna, a Flux-Flow Oscillator (FFO) acting as a Local Oscillator (LO) and a second SIS harmonic mixer (HM) for the FFO phase locking. The concept of the SIR is very promising for many practical applications due to the SIR compactness and a wide tuning range of the FFO. Presently, the frequency range of most practical heterodyne receivers is limited by the tunability of the local oscillator. For a solid-state multiplier chain the fractional input bandwidth typically does not exceed 10 - 15 %. SIR bandwidth is determined by the SIS mixer tuning structure and matching circuitry between the SIS and the FFO; bandwidth up to 30 - 40 % may be achieved with a twin-junction SIS mixer design. To achieve desirable spectral resolution (at least 1 MHz at LO frequency 300 – 700 GHz) local oscillator of the integrate receiver has to be phase-locked to the external reference. Lightweight and compact ultra sensitive superconducting integrated spectrometers are very attractive for space radio astronomy and remote monitoring of the Earth atmosphere using air-crafts, balloons and satellites, where light weight, low power consumption and limited volume are vitally required.
The submillimeter wavelength range is one of the areas where great progress can be expected in astrophysics as soon as high angular resolution and good sensitivity can be achieved. In astrophysics the observations of spectral lines of molecules and dust in space are the main source of information about physical conditions, chemical reactions and processes in star formation regions and interstellar medium. Processes of star formation and evolution of galaxies are among the most fundamental problems of astrophysics, that’s why importance of such observations is doubtless. From the point of view of those observations the most important frequency ranges correspond to mm- and submm-wavelengths, typical for rotational and oscillatory transitions of most molecules observed in space objects and for the peak intensity of interstellar medium radiation.
Besides astrophysical problems it is possible to investigate important problems of atmosphere physics with such an instrument. Remote study of atmospheric pollution is possible using onboard submm wave spectrometers through detection of the spectral lines of ozone, chlorine and other elements, responsible for ozone depletion. Many atmospheric species (e.g. OH, CH, NH, HCl, H2O) has strong radiation and absorption lines in THz spectral range. The integrated spectrometer for the international project TELIS - Terahertz Limb Sounder (frequency range 500 – 650 GHz) has been recently developed by the Kotel'nikov Institute of Radio Engineering and Electronics in tight collaboration with the SRON Netherlands Institute for Space Research. However for many applications in the fields of the Earth atmosphere monitoring and radio astronomy it is very desirable to substantially expand the existing frequency range both up to higher and down to lower frequencies. That is why the project tasks will include development of spectrometer prototype for the radio telescope (frequency range 300 – 400 GHz) as well as an exploration of a possibility to build integrated receivers for frequencies up to 1 THz.
The growing importance of applications in the fields like astronomy and high-altitude atmosphere research, characterized by low levels of background noise and interference, drive the development of high-sensitive spectrometers. But such receivers and technical solutions may as well become the basis for other applications, for example for passive radio thermo-location (or imaging), spectrometers for testing and investigation of new THz sources being developed or spectrometers for non-invasive medical survey. When mass-produced the estimated cost of a microcircuit for an Integrated Spectrometer would be of the order of 1000 USD, much lower than 30 - 35,000 USD presently paid for a conventional oscillator in this frequency range, usually based on a BWO with powerful magnet and high-voltage power supply or a solid-state oscillator with a high-frequency amplifiers and harmonic multiplier. Mass production of integrated spectrometers gives a chance for their application for analysis of the breathed out air at medical survey. Spectral lines most important for medical analysis can be detected by adsorption of submillimeter waves. There is also a large niche for applications of integrated spectrometers for the detection of radiation from the newly developed cryogenic sources of submm waves.
To reach all these goals the following researches will be carried out and the following scientific tasks have to be accomplished:
- Development and optimization of technological process for fabrication of the Nb-AlN-NbN tunnel junctions with current density Jc > 20 kА/см2 and quality factor Rj/Rn more than 10.
- Optimization of the technological procedure for fabrication of the sub-micron SIS tunnel junctions (area as small as 0.3 m2) by using methods of direct electron beam lithography (EBL) and chemical-mechanical polishing (CMP).
- Development and comprehensive investigation of the superconducting local oscillators (FFOs) based on novel types of the tunnel junctions providing possibility of continuous frequency tuning in the frequency range 300 – 700 GHz and autonomous linewidth below 10 MHz to realize spectral ratio > 50 %.
- Development and numerical simulation of new generation of the superconducting integrated circuits for on-board integrated submm spectrometers for atmosphere monitoring and radio astronomy. Fabrication and comprehensive characterization of novel superconducting integrated circuits.
- Optimization of the on-board submm integrated spectrometer for atmosphere monitoring and radio astronomy. Expected parameters are as follows: frequency range 500 - 650 GHz, minimal noise temperature – 150 K, output intermediate frequency 4 – 8 GHz, spectral resolution better than 1 MHz over whole frequency band. Definition of the stability by Allan variance tests and spectral resolution by gas cell measurements.
- Development and characterization of the spectrometer prototype with central frequency 345 GHz, noise temperature no more than 100 K and spectral resolution better than 100 kHz for implementation on a practical radio telescope.
- Exploration of a possibility to build an integrated receiver for frequencies up to 1 THz
- Study of feasibility of the multi-pixel SIR arrays with phase-locked FFO for atmosphere monitoring and radio astronomy.
There is a number of new approaches in the basis of this proposal. The idea of integration of different superconducting components in a single-chip receiver has been developed by IREE scientists. This concept has been experimentally proven in collaboration of the SRON and IREE. A novel and reliable technique, recently proposed by project groups, will be used for precision linewidth measurements and phase locking of superconducting oscillator. New FFO types will be developed and comprehensively investigated in order to realize FFO phase locking in the entire frequency range 300 – 700 GHz. Integrated spectrometers developed in the course of the project realization would be a prototype for planned missions aimed at the investigation of submm radiation using space borne radio telescopes. Thus on the base of novel tunnel nanostructures a number of new devices attractive for practical applications (global security, environmental technologies, radio astronomy, Earth atmosphere monitoring, and medical diagnostic) will be developed and tested.
It is important to emphasize that most of the project study will be done in the collaboration with the leading western scientific institutions, which are interested in project results and will provide their own unique technological and measuring facilities for project execution (see appended Letters of Support). Unique microwave cryogenic measuring set-ups available at SRON Netherland Institute of Space Researches (Groningen, the Netherlands), Technical University of Denmark (Lyngby) and Physikalisches Institut - Universitaet Karlsruhe (Karlsruhe, Germany) will be involved. Furthermore, some of the foreign collaborators are ready to supply Russian partners (using the ISTC infrastructure) by a set of modern equipment in case of funding of the project by ISTC.
The project undoubtedly fits the aims and tasks of ISTC. It allows a large group of Russian scientists and engineers from IREE and IPM, having great knowledge and qualification in development of military applications, to be reoriented completely onto the peaceful applications. Thereby any possibilities of contacts with the developing countries on transferring special knowledge and research results for military applications will be completely cancelled.
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