Optical Lumped Element Microwave Kinetic Inductance Detectors

Microwave Kinetic Inductance Detectors, or MKIDs, have proven to be a powerful cryogenic detector technology due to their sensitivity and the ease with which they can be multiplexed into large arrays. An MKID is an energy sensor based on a photon-variable super conducting inductance in a lithographed microresonator. It is capable of functioning as both a photon detector across the electromagnetic spectrum and a particle detector. We have recently demonstrated the world's first photon-counting, energy-resolving, ultraviolet, optical, and near infrared MKID focal plane array in the ARCONS camera at the Palomar 200" telescope. Optical Lumped Element (OLE) MKID arrays have significant advantages over semiconductor detectors such as charge coupled devices (CCDs). They can count individual photons with essentially no false counts and determine the energy (to a few percent) and arrival time (to approximate to 1 mu s) of every photon, with good quantum efficiency. Initial devices were degraded by substrate events from photons passing through the Titanium Nitride (TiN) material of the resonator and being absorbed in the substrate. Recent work has eliminated this issue, with a solution found to be increasing the thickness of the TiN resonator from 20 to 60 nm.