Lumped-element kinetic inductance detectors (LEKIDs) have recently shown considerable promise as direct-absorption
mm-wavelength detectors for astronomical applications. One major research thrust within the Néel Iram Kids Array (NIKA)
collaboration has been to investigate the suitability of these detectors for deployment at the 30-meter IRAM telescope located
on Pico Veleta in Spain.
Compared to microwave kinetic inductance detectors (MKID), using quarter wavelength resonators, the resonant circuit of
a LEKID consists of a discrete inductance and capacitance coupled to a feedline. A high and constant current density
distribution in the inductive part of these resonators makes them very sensitive. Due to only one metal layer on a silicon
substrate, the fabrication is relatively easy.
In order to optimize the LEKIDs for this application, we have recently probed a wide variety of individual resonator and
array parameters through simulation and physical testing. This included determining the optimal feed-line coupling, pixel
geometry, resonator distribution within an array (in order to minimize pixel cross-talk), and resonator frequency spacing.
Based on these results, a 32-pixel Aluminum array was fabricated and tested in a dilution fridge with optical access, yielding
an average optical NEP of ~7.2 x 10-16 W/Hz^1/2. In October 2009 a first prototype of LEKIDs has been tested at the IRAM
30 m telescope and first astronomical results have been achieved.