CC BY
2On the possibility of measuring the number of THz photons using a superconducting HEB bolometer
T. Novikova1, K. Kuznetsov1, I. Korolev1, P. Prudkovskii1, G. Kitaeva1*
1- Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991 Russia
* [email protected]. ru
We study statistical distributions of output signals of a superconducting HEB detector [1] exposed to weak photon pulses of 1 THz frequency. The pulses with variable photon numbers were generated under strongly non-degenerate parametric down-conversion (PDC) in Mg: LiNbO3 crystal cooled down to 4.8 K [2]. The experiments were carried out in two different PDC pumping modes, with the laser pulse durations of 28 ps and 10 ns.
It is shown that statistical distributions of signals obtained under irradiation by nanosecond pulses contain information about the mean number of discrete photon-counting events [3]. The nanosecond-mode histograms were successfully modeled as sums of discrete contributions with Gaussian statistics and taking into account Poisson statistics for the numbers of these events. Dependence of the approximation parameters on the PDC pump power totally corresponds to theoretical predictions concerning the numbers of incident THz photons.
At the same time, switching to the picosecond irradiation mode totally changes the main features of the statistical distributions of signals from the same HEB detector. The discrete structure disappears when the irradiation time intervals become less than the detector temporal resolution ~50 ps. The average output signals remain still proportional to the number of incident photons. But the histogram shapes and the signal dispersions do not change when the number of incident photons increases starting from the zero (dark noise) level.
Various scenarios of processes occurring when a superconducting HEB detector is irradiated by several THz photons are discussed, as well as the parameters of photon pulses capable of detecting individual photons.
The work was done under financial support of the Russian Science Foundation (Grant No. 22-1200055).
[1] S. Seliverstov, S. Maslennikov, S. Ryabchun, M. Finkel, T. M. Klapwijk, N. Kaurova, Yu. Vachtomin, K. Smirnov, B. Voronov, G. Goltsman, Fast and sensitive terahertz direct detector based on superconducting antenna-coupled hot electron bolometer, IEEE Trans. Appl. Supercond., vol. 25, No. 2300304 (2015).
[2] A. Leontyev, K. Kuznetsov, P. Prudkovskii, D. Safronenkov, G. Kitaeva, Direct measurement of the correlation function of optical-terahertz biphotons, JETP Letters, vol.114, pp. 565-571 (2021).
[3] P. Prudkovskii, A. Leontyev, K. Kuznetsov, G. Kitaeva, Towards measuring terahertz photon statistics by a superconducting bolometer Sensors, vol. 21, p. 4964 (2021).
