Superconducting integrated THz receivers: development and applications

Abstract

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 receiver's 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.

Electrothermal behavior and terahertz emission properties of a planar array of two Bi2Sr2CaCu2O8+δintrinsic Josephson junction stacks

“…The frequency of the local oscillator is continuously tunable from 350 to 750 GHz, while the SIS mixer is effectively matched to the planar antenna between 450 and 700 GHz, limiting the SIR operation range. A frequency resolution of the SIR well below 100 kHz has been confirmed [57].…”

Superconducting Integrated Terahertz Spectrometers

“…Continuous tuning of the phase-locked local oscillator has been realized at any frequency in the range 300-750 GHz [3], [4]. The output power of the FFO is sufficient to pump the matched SIS mixer in a wide frequency range and can be electronically adjusted.…”

“…Capability of the SIR for high-resolution spectroscopy has been successfully proven also in laboratory environment by gas cell measurements. The possibility to use SIR devices for the medical analysis of exhaled air has been demonstrated [3]. Many medically relevant gases have spectral lines in the sub-terahertz range [7] and can be detected by a SIR-based spectrometer.…”

“…The FFO free-running linewidth has been measured between 0.3 and 5 MHz, resulting in the spectral ratio of the phase-locked FFO above 70% over the range. As a result of receiver optimization, the DSB noise temperature was measured below 100 K, which is about ; the spectral resolution is well below 1 MHz [3], [4].…”

Spectral measurements of THz radiation emitted from intrinsic Josephson junction stacks

“…The observed rotation frequencies of ammonia (572.498 GHz) coincide with literature values. Further improvement of the lowest resolvable linewidth is possible by using proper feedback techniques for the oscillator [10].…”