  Current technologies for infrared detection have been based on epitaxially
grown semiconductors. Here we review some of the recent developments relative
to colloidal nanocrystals and their use as building blocks for the design of
low-cost infrared sensors. We focus on HgTe nanocrystals which appear as the
only material leading to infrared photoconductivity and ultra-broad spectral
tunability: from the visible to the long-wave infrared. We review some of the
important results which demonstrated that colloidal nanocrystals can be
compatible with air stable operations, fast detection, and strong absorption.
We discuss the recent progresses relative to multipixel devices and show
results obtained by coupling short-wave infrared nanoparticles with CMOS
circuits to achieve video rate VGA format imaging. In particular we present
that nanocrystals are a promising material for long range (>150 m) active
detection in both continuous wave and pulsed mode with a time resolution down
to 10 ns.
