Electrodynamic simulation of an antenna-coupled Pb–graphene–Pb Josephson junction at millimeter wavelengths

Abstract Potential for single-photon mm-wave detection by antenna-coupled Pb–graphene–Pb Josephson junctions (JJ) is evaluated. We consider the high-speed “video” (non-thermal) detection based on Shapiro steps induced by antenna-sourced AC currents across the JJ. Electrodynamic simulation informs the bowtie antenna design and estimates the AC current through JJ. Standard JJ models are used to estimate the corresponding AC voltage and the downward shift of the maximum zero-voltage DC current I c , where a sharp transition occurs in the DC voltage–current curve. Calculated voltage responsivity for current biasing near I c is compared with Johnson noise to estimate a lower limit for noise equivalent photon flux. Estimated responsivity is 0.9 $$MV/W$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>M</mml:mi> <mml:mi>V</mml:mi> <mml:mo>/</mml:mo> <mml:mi>W</mml:mi> </mml:mrow> </mml:math> at 300 $$GHz$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>GHz</mml:mi> </mml:mrow> </mml:math> , and the lower bound on the noise equivalent power is 0.11 fW/ $$\sqrt {{\text{Hz}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mtext>Hz</mml:mtext> </mml:msqrt> </mml:math> giving a 2 photons per microsecond. Graphical abstract