Fast nonlinear photoresponse of current biased thin-film Bi2Sr2CaCu2O8 to pulsed far-infrared radiation

Abstract

The response of a polycrystalline thin-film Bi2Sr2CaCu2O8 superconducting stripe to short-pulse far-infrared (λ=447 μm) radiation is reported. Under constant current bias, a photosignal is generated when the maximum zero voltage current is exceeded. Measurements of the sensitivity as a function of temperature, bias current, and intensity reveal the signal source to be nonbolometric. The response is found to obey a (power)1/2 law over more than 2 orders of magnitude. We believe the detection mechanism arises from the interaction of grain boundary Josephson junctions with radiation induced screening currents.