Sergey I. Pripolzin

Superconducting integrated THz receivers: development and applications

A Superconducting Integrated Receiver (SIR) comprises on one chip all elements needed for heterodyne detection: a low-noise 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. Light weight and low power consumption combined with nearly quantum limited sensitivity and a wide tuning range of the FFO make SIR a perfect candidate for many practical applications. In particular, the SIR developed for novel balloon borne instrument TELIS (TErahertz and submillimeter LImb Sounder) covers frequency range 480 - 650 GHz. As a result of recent receivers optimization the DSB noise temperature was measured as low as 120 K for the SIR with intermediate frequency (IF) band 4 - 8 GHz. The capability of the SIR for high resolution atmospheric spectroscopy has been successfully proven with scientific balloon flights from Kiruna, North Sweden. Diurnal cycles of ClO and BrO has been observed with BrO line level of only about 0.5 K. Possibility to use the SIRs for analysis of the breathed out air at medical survey has been demonstrated.

Two-Frequency THz Spectroscopy for Analytical and Dynamical Research

Development of high-sensitivity and high resolution analytical spectroscopy is an area of active research interest currently. In the paper a method of two-frequency THz spectroscopy is presented. A laboratory model of spectrometer using two independent radiation sources of 118-178 GHz and 330-390 GHz ranges and a single detector with 500-2500 V/W sensitivity is presented. Test measurements allowed detecting two gases simultaneously with the minimal registration period of 4 μs and the hardware resolution of 1 kHz. These experiments proved this new trend in analytical spectroscopy to have wide application prospects for a variety of fundamental and applied scientific problems. In the first place, it is laboratory modeling of the processes of atmospheric and space chemistry, studying of their dynamics as well as transformations and changes of mixture composition. Besides, the proposed method can be applied to investigations of fast processes, detection of intermediate and short-lived products of chemical reactions.

Integrated Submm Wave Receiver: Development and Applications

A superconducting integrated receiver (SIR) comprises in a single chip a planar antenna combined with a superconductor-insulator-superconductor (SIS) mixer, a superconducting Flux Flow Oscillator (FFO) acting as a Local Oscillator (LO) and a second SIS harmonic mixer (HM) for the FFO phase locking. In this report, an overview of the SIR and FFO developments and optimizations is presented. Improving on the fully Nb-based SIR we have developed and studied Nb–AlN–NbN circuits, which exhibit an extended operation frequency range. Continuous tuning of the phase locked frequency has been experimentally demonstrated at any frequency in the range 350–750 GHz. The FFO free-running linewidth has been measured between 1 and 5 MHz, which allows to phase lock up to 97% of the emitted FFO power. The output power of the FFO is sufficient to pump the matched SIS mixer. Therefore, it is concluded that the Nb–AlN–NbN FFOs are mature enough for practical applications.These achievements enabled the development of a 480–650 GHz integrated receiver for the atmospheric-research instrument TErahertz and submillimeter LImb Sounder (TELIS). This balloon-borne instrument is a three-channel superconducting heterodyne spectrometer for the detection of spectral emission lines of stratospheric trace gases that have their rotational transitions at THz frequencies. One of the channels is based on the SIR technology. We demonstrate for the first time the capabilities of the SIR technology for heterodyne spectroscopy in general, and atmospheric limb sounding in particular. We also show that the application of SIR technology is not limited to laboratory environments, but that it is well suited for remote operation under harsh environmental conditions. Light weight and low power consumption combined with broadband operation and nearly quantum limited sensitivity make the SIR a perfect candidate for future airborne and space-borne missions. The noise temperature of the SIR was measured to be as low as 120 K in double sideband operation, with an intermediate frequency band of 4–8 GHz. The spectral resolution is well below 1 MHz, confirmed by our measurements. Remote control of the SIR under flight conditions has been demonstrated in a successful balloon flight in Kiruna, Sweden.Capability of the SIR for high-resolution spectroscopy has been successfully proven also in a laboratory environment by gas cell measurements. The possibility to use SIR devices for the medical analysis of exhaled air will be discussed. Many medically relevant gases have spectral lines in the sub-terahertz range and can be detected by an SIR-based spectrometer. The SIR can be considered as an operational device, ready for many applications.

Development of the physical principles of the design and implementation of a 500–700 GHz spectrometer with a superconducting integrated receiver

A spectrometer based on the effect of freely decaying polarization in the frequency range 500–700 GHz has been designed. Radiation sources are harmonics from a quantum semiconductor superlattice frequency multiplier. The receiving system of this spectrometer is constructed using a superconducting integrated receiver based on a superconductor-insulator-superconductor mixer and a flux-flow oscillator operating as a heterodyne oscillator. The spectrometer has been used to measure absorption lines of NH3 in a sample of expired air (572 GHz).

Using the methods of multi-frequency spectroscopy for sensing

Nowadays the development of analytical spectroscopy with high performance, sensitivity and spectral resolution is attended. In the paper the method of two-frequency THz spectroscopy as well as the laboratory model of the spectrometer with using two independent radiation sources and a single detector of THz radiation are presented. The preliminary measurements have testified this new direction of analytical spectroscopy to open widespread trends of its using for various basic and applied problems of physics, chemistry, astronomy, medicine and biology. First of all, there are laboratory modeling the processes of atmospheric and space chemistry, studying of their dynamics as well as transformations and changes of mixture composition. Besides, the method presented can be applied for investigations of fast processes, detecting the intermediate and short time living products of chemical reactions.

Multifrequency high precise subTHz-THz-IR spectroscopy for exhaled breath research

Nowadays the development of analytical spectroscopy with high performance, sensitivity and spectral resolution for exhaled breath research is attended. The method of two-frequency high precise THz spectroscopy and the method of high precise subTHz-THz-IR spectroscopy are presented. Development of a subTHz-THz-IR gas analyzer increases the number of gases that can be identified and the reliability of the detection by confirming the signature in both THz and MIR ranges. The testing measurements have testified this new direction of analytical spectroscopy to open widespread trends of its using for various problems of medicine and biology. First of all, there are laboratory investigations of the processes in exhaled breath and studying of their dynamics. Besides, the methods presented can be applied for detecting intermediate and short time living products of reactions in exhaled breath. The spectrometers have been employed for investigations of acetone, methanol and ethanol in the breath samples of healthy volunteers and diabetes patients. The results have demonstrated an increased concentration of acetone in breath of diabetes patients. The dynamic of changing the acetone concentration before and after taking the medicines is discovered. The potential markers of pre-cancer states and oncological diseases of gastrointestinal tract organs have been detected. The changes in the NO concentration in exhaled breath of cancer patients during radiotherapy as well as increase of the NH3 concentration at gastrointestinal diseases have been revealed. The preliminary investigations of biomarkers in three frequency ranges have demonstrated the advantages of the multifrequency high precise spectroscopy for noninvasive medical diagnostics.

Analysis Of Noise Characteristics And Noise Generation In SubTHz And THz Frequency Ranges

Noise characteristics of subTHz and THz devices (mixers, detectors) based on Schottky diodes and quantum superlattice diodes (SL‐diodes) are presented. The test bench for measurements of device’s characteristics is elaborated. Noise generator of THz frequency range based on SL‐diodes multiplier and mm noise generator is also demonstrated.

Fast sweep solid state spectrometer for sub-THz and THz frequency ranges

The design and development of a fast sweep submillimeter and THz spectrometer based on solid-state components is presented. A prototype laboratory model of such a spectrometer will be described and some performance characteristics as well as potential applications emphasized.

Solid state nonstationary spectrometers SUBTHz and THz frequency ranges for analytical applications

In the paper we present a new approach to development of a time-domain (pulse Furier-transform) spectroscopy method in subTHz and THz frequency ranges with maximal sensitivity and spectral resolution. In our studies we obtained harmonics up to 2.7 THz with application of multipliers based on quantum superlattice structures. Our spectrometer includes subTHz and THz emission sources based on phase-stabilized Gunn generators and quantum superlattice structures multipliers and mixers (up-converter). This approach ensures narrow instrumental linewidth less than 10 kHz over the operating range of the spectrometer as well as development of software for computer control and data acquisition. In the paper we propose two possible schemes of spectrometers realization. These variants of spectrometer are suitable, in particular, for atmospheric investigations, including detection of water, acetone, NO, CO etc.