Terahertz pulse driven Josephson junctions

The voltage response of a Josephson junction to a pulsed terahertz current is evaluated in the limit of a negligible junction capacitance (overdamped limit). The time-dependent superconductor phase difference across the junction is calculated in the framework of the standard resistive shunted junction model by using a perturbative method. The pulsed current bias affects the time average value of the voltage across the junction and current steps are induced in the current–voltage characteristics for voltage values depending on the pulse repetition rate. The current step height is proportional to the square of the pulse time width (τ) to the period (T) ratio. A fast response detector for pulsed Terahertz radiation is proposed, with an expected responsivity of the order of 0.1 V/W and an equivalent noise power of about 3 × 10−10 W/Hz1/2.

► Theoretical model of the ac Josephson effect in pulsed current driven junctions.
► Evaluation of the voltage response of a THz pulsed radiation driven Josephson junction.
► The pulsed current bias induces steps in the junction I/V characteristics for voltages depending on the pulse rate.
► Working principles of a fast response detector for THz pulsed radiation.