Superconducting nanowire single-photon detectors (SNSPDs) are revolutionizing fields such as quantum technologies, astronomy, and biomedical imaging with their exceptional performance metrics. This dissertation introduces local helium ion irradiation to further enhance these detectors. Three approaches are demonstrated: site-selective enhancement transforming thick-film detectors from 55% efficiency, elimination of current crowding, and thermal conductance engineering. These innovations open new pathways to next-generation single-photon detectors.
