Energy resolution of terahertz single-photon-sensitive bolometric detectors

Abstract

We report measurements of the energy resolution of ultra-sensitive superconducting bolometric detectors. The device is a superconducting titanium nanobridge with niobium contacts. A fast microwave pulse is used to simulate a single higher-frequency photon, where the absorbed energy of the pulse is equal to the photon energy. This technique allows precise calibration of the input coupling and avoids problems with unwanted background photons. Present devices have an intrinsic full-width at half-maximum energy resolution of approximately 23 terahertz, near the predicted value due to intrinsic thermal fluctuation noise.

Development of the nano-HEB array for low-background far-IR applications

“…Electrical NEP TEF derived from those measurements was as low as ~ 10 -18 W/Hz 1/2 for smallest devices at 350 mK. Using a novel microwave technique [8] based on generation of short 20-GHz pulses imitating THz photons, we measured the energy resolution in similar nano-HEBs and found that Δε FWHM /h ≈ 23 THz is feasible at 300 mK.…”

“…This resolution remains unchanged from 50 mK to 150 mK and then degrades at ~ 200 mK completely disappearing near T C . In the previous work [8] we determined the minimal resolved energy Δε FWHM /h = 23 THz at 300 mK, which was close to so the called "thermodynamic limit" ~ € k B C e T C 2 . Device #1 has similar volume and slightly higher T C but nevertheless the energy resolution is noticeably worse.…”

“…It has been predicted [1,7] that the energy resolution in ultimately small submicron-size nano-HEBs can be sufficient for detection of 1 THz photons at 300 mK with extremely low dark count rate. Larger devices (similar to devices #1 and #2) have been recently studied using a microwave technique substituting the real photons with equivalent short pulses of 20 GHz radiation ("fauxtons") which were easy to generate and to efficiently coupled to the nao-HEB [8].…”

A Novel Particle/Photon Detector Based on a Superconducting Proximity Array of Nanodots

“…Such devices can identify particles and/or photons in the long wavelength, optical, and x-ray range using thermal (bolometric) or non-bolometric effects [4]. However, in general, for the low frequency regime up to microwave/IR wavelengths the photon energy is too small with respect to the noise floor and the response is mainly due to the large number of absorbed photons In the high frequency domain, from the visible to the x-ray domain, such detectors are sensitive enough to probe the signal due to the absorption of a single photon or a single particle [5] Nevertheless, at present, the energy resolution of the best ultrasensitive single photon superconducting bolometric detectors show, down to approximately 20 GHz, an energy resolution near the ideal values due to the intrinsic thermal fluctuation noise [6].…”

“…A device based on a non-bolometric effect may lead to the detection even of a single photon, for example considering the radiation frequency in the internal Josephson oscillation range, i.e., from megahertz to gigahertz, up to the terahertz domain synchronization effects know as Shapiro steps occur. In this case we detect a jump of the current when the average voltage is an integer multiple of the AC frequency divided by the Josephson constant 2e/h = 483597011 GHz/V [1][2][3][4][5][6][7][8][9][10][11][12] Another non-bolometric device could be made with a "superconducting nanowire" 100 nm wide. This simple device may operate at a temperature well below the superconducting transition temperature of the corresponding film when the sample is biased just below the critical current.…”