Hot electron energy relaxation time in vanadium nitride superconducting film structures under THz and IR radiation

Abstract

The paper presents the experimental results of studying the dynamics of electron energy relaxation in structures made of thin (d ≈ 6 nm) disordered superconducting vanadium nitride (VN) films converted to a resistive state by high-frequency radiation and transport current. Under conditions of quasi-equilibrium superconductivity and temperature range close to critical (~ Tc), a direct measurement of the energy relaxation time of electrons by the beats method arising from two monochromatic sources with close frequencies radiation in sub-THz region (ω ≈ 0.140 THz) and sources in the IR region (ω ≈ 193 THz) was conducted. The measured time of energy relaxation of electrons in the studied VN structures upon heating of THz and IR radiation completely coincided and amounted to (2.6–2.7) ns. The studied response of VN structures to IR (ω ≈ 193 THz) picosecond laser pulses also allowed us to estimate the energy relaxation time in VN structures, which was ~ 2.8 ns and is in good agreement with the result obtained by the mixing method. Also, we present the experimentally measured volt-watt responsivity (S~) within the frequency range ω ≈ (0.3–6) THz VN HEB detector. The estimated values of noise equivalent power (NEP) for VN HEB and its minimum energy level (δE) reached NEP@1MHz ≈ 6.3 × 10–14 W/√Hz and δE ≈ 8.1 × 10–18 J, respectively.

Broadband Photodetectors and Imagers in Stretchable Electronics Packaging

“…Some thermal THz sensors have been reported to achieve ultrahigh sensitivity by cooling to extremely low temperatures to suppress thermal noise. [98][99][100] The detection principles of photonics can be classified into linear and nonlinear responses. In the linear mechanism, sensors are designed to absorb and emit the same energy levels as the THz light using quantum wells and Landau levels.…”

“…Some thermal THz sensors have been reported to achieve ultrahigh sensitivity by cooling to extremely low temperatures to suppress thermal noise. [ 98–100 ]…”

Towards Measuring Terahertz Photon Statistics by a Superconducting Bolometer

“…They could be tested by detecting low-photon fluxes, but usually the fluxes are too high due to the thermal background radiation at room temperatures. In our work, we study the capabilities of this type of detectors, namely, superconducting hot-electron bolometers (HEB) [ 30 , 31 , 32 , 33 ], to find the way for connecting statistical distributions of their analog signal with statistics of the input THz photons. A necessary and important point of this research was a special creation of a THz source with low and easy-controllable mean number of THz photons per mode.…”

Fundamental Limits of Few-Layer NbSe2 Microbolometers at Terahertz Frequencies

“…Another crucial parameter of superconducting HEBs is their response time ,,, τ. To determine τ in our NbSe 2 detectors, we used a standard heterodyne mixing scheme (Supporting Information). In short, the scheme employs two BWOs called signal (RF) and local (LO) oscillators, which generate radiation with slightly dissimilar frequencies f RF = 130 ± 1 GHz and f LO = 129 GHz, respectively (Figure a).…”