Light-concentrating microcone array for improving performance of infrared imaging devices

Light-harvesting low-index
$(n=1.6)$
microconical arrays are proposed for increasing the sensitivity and the signal-to-noise ratio (SNR) of mid-wave infrared (MWIR) focal plane arrays (FPAs) used in thermal cameras. Numerical modeling showed a 3-D Power enhancement factor ~ 50 in MWIR for 10° tapered microcones with
$D_{\mathrm{t}}/D_{\mathrm{b}}=60\\mu \mathrm{m}/8\mu \mathrm{m}$
and
$h=150\mu\mathrm{m}$
, where
$D_{\mathrm{t}}$
and
$D_{\mathrm{b}}$
are the top and bottom diameters of microcones, respectively. Such microconical arrays were fabricated in photoresist by using a nanoscribe tool directly on top of the front-illuminated Ni/Si Schottky-barrier, and three-fold enhancement in the photocurrent response was observed. The proposed approach permits increase of the SNR and the operation temperature of the MWIR imaging devices.