Response of a SINIS detector with electron cooling to submillimeter-wave radiation

The response of a detector fabricated on a silicon substrate in the form of a metamaterial that is a $10 \times 10$ matrix of split rings containing superconductor-insulator-normal metal-insulator-superconductor tunnel structures to submillimeter wave radiation has been experimentally studied. At voltages below the superconducting gap, the electron temperature $T_e$ at the substrate temperature $T \sim 0.1$ K is $\sim0.23$ K due to overheating by spurious radiation. At the substrate temperature $T \sim 0.3$ K, the electron temperature is close to the substrate temperature $T_e\approx T$. In both cases, with increasing voltage, $T_e$ decreases due to electron cooling and reaches $0.19$ K at a voltage corresponding to the maximum response. The response at $T = 0.1$ K is greater than that at $T \sim 0.3$ K by a factor of $5$–$6$. Thus, cooling of only electrons does not provide the same responsivity as cooling of the detector as a whole.