We have developed Microwave Kinetic Inductance Detectors suitable for near-IR single photon counting. Our films are made of titanium and titanium nitride, deposited in a multi-layer structure Ti/TiN/Ti/TiN with a total thickness of 44 nm. The film has a transition temperature of 1.2 K and a surface kinetic inductance of 34 pH/sq. The resonator was designed with lumped elements and consists of two blocks of interdigitated capacitors connected by a meandered stripe inductor of 128 μm$^3$. The resonator resonance frequency is 6.8 GHz and the internal quality factor is 125000. We have estimated the kinetic inductance fraction α=0.86 .The detector is read out with the usual homodyne scheme and has been calibrated with light pulses produced by a laser diode with wavelength 1550 nm. We measure a FWHM energy resolution = 0.44 eV which is sufficient to resolve events with up to 4 photons and is within a factor of two from the best value published in literature. In the next design we aim at a further improvement by reducing the inductor volume by about a factor of 10.
|Less than 5 years of experience since completion of Ph.D||N|
|Student (Ph.D., M.Sc. or B.Sc.)||N|