Two-dimensional plasmonic grating for increased quantum efficiency in midwave infrared nBn detectors with thin absorbers.

We demonstrate a strategy for increasing the operating temperatures of nBn midwave infrared (MWIR) focal plane arrays, based on the use of two-dimensional plasmonic gratings to enhance the quantum efficiency (QE) of structures with very thin absorbers. Reducing the absorber volume correspondingly reduces the dark current in a diffusion-limited photodiode, while light trapping mediated by the plasmonic grating increases the net absorbance to maintain high QE. The plasmonically enhanced nBn MWIR sensors with absorber thicknesses of only 0.5 µm exhibit peak internal QEs as high as 57%, which enables a 5-fold reduction in dark current. Numerical simulations indicate the potential for further improvement.

Mid-infrared vertical-cavity surface-emitting lasers for chemical sensing.

The first (to our knowledge) III-V mid-IR vertical-cavity surface-emitting lasers (lambda = 2.9 microm) are demonstrated and show promising characteristics for chemical detection applications. The cw optical-pumping threshold is low (4 mW at 80 K) and efficiency is high (5.6% W/W). Pulsed operation is obtained up to 280 K and cw up to 160 K. Lateral-mode confinement will lead to spectrally pure, single-mode output for chemical identification.