Electrodynamic theory for the operation principle of a superconducting kinetic inductance stripline detector

Generation and transmission of voltage signals in a kinetic inductance detector made of a superconducting nanowire stripline is investigated on the basis of superconducting electromagnetism. We show that electric signals traveling along the stripline in this detector can be regarded as a Swihart mode. An equation which can describe the generation and transmission of voltage pulses in this detector is derived. A pair of voltage pulses with opposite polarities are created when a spatiotemporal variation in the density of the superconducting condensate occurs in a small region of this superconducting nanowire. The voltage pulses propagate along the stripline in the directions opposite to each other with the Swihart velocity. The characteristic of the radiation detector named current-biased kinetic inductance detector (CB-KID) is well described by our model. (paper)