Microbolometer for Astrophysics Observations
Investigation and Development of the Ultrahighsensitive Terahertz Frequency Band Hot-Electron S-LN-S Microbolometer for Extra Atmosphere Astrophysics Observations and Measurements
Tech Area / Field
- SAT-EXP/Extraterrestrial Exploration/Space, Aircraft and Surface Transportation
- INS-MEA/Measuring Instruments/Instrumentation
- INF-SIG/Sensors and Signal Processing/Information and Communications
8 Project completed
Senior Project Manager
Russian Academy of Sciences / Institute of Radioengineering and Electronics, Russia, Moscow
- P.L.Kapitza Institute of Physics Problems, Russia, Moscow\nMoscow State University / Department of Physics, Russia, Moscow\nFIAN Lebedev / Astro Space Center, Russia, Moscow
- NIST / Boulder Colorado Laboratories, USA, CO, Boulder\nCalifornia Institute of Technology / Jet Propulsion Laboratory, USA, CA, Pasadena
Project summaryAt present in a number of fundamental physical problems one of problems is the observation of the celestial sphere in the terahertz (500 – 3,000 GHz) frequency band of electromagnetic spectrum as well as the localization and measurements of spatial, time and spectral characteristics of sources of observed radiation with the purpose of further broadening of our knolidge about the structure of the Universe and events developing in it. Besides the problem of investigation of nearest Earth environment – upper rarefied layers of the atmosphere – by means of the measurement of their radiation in mentioned above frequency band with the aim of study an ozone condition, environmental pollution etc. does exist.
To attack this problems supersensitive receivers of 500 – 3,000 GHz frequency band are necessary. Among such receivers bolometers are very important and among them there is one of most promissing bolometers based on the heating electrons in the thin film of normal metal with electrodes of metal-superconductor (the S-lN-S structure, where “S” means the superconductor and “lN” means the long film of normal metal), cooled down to extremely low temperatures of order of 100 – 200 mK. Preliminary estimations and measurements [1-3] show the possibility to reach the noise equivalent power of such bolometer up to 10-18 W/ Hz1/2 in said above frequency band. Important elements of S-lN-S bolometer are superconducting electrodes on the ends of the film of normal metal. They prevent a leak of the electron energy out of normal metal film owing to Andreev reflection at the boundary between the lN-film and S-electrodes. This phenomenon reduces in high rate the heat losses of electrons in the film and thus improves in high rate the effectiveness of the heating electrons by the radiation.
The problem of investigation and development of the S-lN-S bolometer based on said above principles can be devided into the following stages: 1. Investigation of electrons movement processes including the heating of the electron gas in structures consisting of the normal metal thin film with superconductor electrodes (S-lN-S structures); investigation of the procedure of measurement of the temperature of electron gas in S-lN-S structure using S-I-N-junction. 2. Investigation of the terahertz frequency band radiation absorbtion in S-lN-S-structures and the heating of the electrons owing to this asorbtion. 3. Investigation of noise processes in S-lN-S- and S-I-N-structures. 4. Optimization of material and geometry parameters of S-lN-S bolometer, radiation input structure into the working element of the bolometer and detected signal output structure with the purpose to obtain maximum available signal-to-noise ratio. 5. Development of the technology for the manufacturing of the working thin film S-lN-S-element of the bolometer and S-I-N-junction for electron gas temperature measurements. 6. Classification of tasks of observations and measurements of the space radiation sources in the terahertz frequency band and the formulation of starting data for the designing of the receiver with the S-lN-S-bolometer. 7. Development of the design of the receiver with S-lN-S-bolometer including the radiation input structure into the working element of the bolometer and detected signal output structure. 8. Development of the combining system to join the receiver based on the S-lN-S-bolometer and satellite cryostat and the formulation of the technical requirements for the aboard microcooler. 9. Development and manufacturing of experimental prototype of aboard microcooler meeting main provisions of the technical requirements. 10. Development of the procedure for the measurement of the noise equivalent power of the receiver based on S-lN-S-bolometer and creation of the corresponding measurement instrumentation. 11. The carrying out the tests of the reciver with S-lN-S-bolometer in the pototype of aboard microcooler by the Commission of ISTC and the formulation of the technical requirements for the design of the regular aboard receiver.
In this Project the unique physical methods and the technologies like physics and technology of superconducting microcircuits, comprising elements of submicron dimensions, physics and technology of ultra low temperatures in satellite conditions, in particular the prototype of aboard microcooler for temperatures up to 50 mK, will be created, physics and technology of terahertz circuitry including instrumentation for precise measurements on the quantum noise level will be used and gained.
The main expected result of the Project fulfilment has to be the creation of new in principle unique aboard satellite device – supersensitive receiver – technologically complicated in five aspects: 1. Terahertz radio frequency band, transitional between radio frequency and optical frequency bands; 2. Super low temperature region of order up to ~50 mK; 3. Extremely low noise level of order of ~100 mK; 4. Submicron integrated curcuit technology; and 5. The good efficiency preserving after the rocket launch and the operation in aboard and weightlessness conditions. This device will open an opportunity to carry out wide scale obsevations and measurements of weak terahertz electromagnetic sources of the celestial sphere and nearest extraatmosphere Earth vicinity impossible earlier because nobody has made such device including proposed receiver yet. In comparison with the nearest competitor – “spider web” bolometer  – the proposed bolometer not being inferior in its main characteristics, first of all in the noise equivalent power, will have the following advantages: more simple design and manufacturing technology, more than three orders smaller time constant and no special measures have to be taken to prevent microphone effect.
On the way of the achievment of this main result one may expect a number of important intermediate results without which the main result cann’t be achieved. They are:
1. More detailed understanding of the important physical phenomenon – the Andreev reflection of electrons at the normal metal – superconductor boundary – which besides the S-lN-S-bolometer is using or taking place in other devices and structures will be obtained.
2. The integrated superconductor microcircuit technology with submicron (up to 0.2 m dimensions) elements will be moved forward.
3. Prototypes of microcoolers up to deep low temperatures (~0.1 K) suitable for the application together with electronic devices on the spacecrafts will be created.
4. Low frequency (~104 – 105 Hz) amplifier with ultimate low noise level (~0.1 K) for unique precise electrical measurements will be created.
5. Further development of the precise technology and metrology of terahertz frequency band will take place: quasi-optical structures for the radiation input and focucing into elements being small in comparison with wavelength, including ones at super low temperatures, will be created; the precise methods of measurement of the ultimate high noise equivalent power of receiving devices (up to ~10-18 W/Hz1/2 what is corresponded to the noise temperature ~0.1 K) will be improved as well.
1) Design analysis of a novel hot-electron microbolometer, M. Nahum, P.L. Richards and C.A. Mears, IEEE Trans. on Appl. Supercond., 3 (1), March 1993, pp. 2124-2127.
2) Ultrasensitive-hot-electron microbolometer, M. Nahum and John M. Martinis, Appl. Phys. Lett., 63 (22), 29 November 1993, pp. 3075-3077.
3) Andreev reflection based normal metal hot-electron bolometer for space applications, A.N. Vystavkin, D. Chouvaev, L. Kuzmin, M. Tarasov, P. Sundquist, M. Willander and T. Claeson, Presented to 4th International Conference on Millimeter and Submillimeter Waves and Applications, July 20-22, 1998, San Diego, USA.
4) A monolithic bolometer array suitable for FIRST, J. J. Bock, H.G. LeDuc, A.E. Lange, J. Zmuidzinas, An ESA Symposium devoted to the Far InfraRed and Submillimeter Telescope (FIRST) mission, 15-17 April 1997, Institut de Radio Astronomie Millimrtrique, Grenoble, France, pp. 349-352.