Infrared detection by an atomic vapor quantum counter

An efficient technique for the detection of nartowband infrared radiation by up-conversion in an optically saturated atomic vapor is described. The strong transition cross sections provided by the resonance interactions combined with the narrow Doppler spectral response profile contribute to the potential to approach quantum-noise-limited performance. Experimental results confirm the model of the detection process for sodium transitions at 1.48, 2.34, and 3.42 μ. The predicted ultimate noise equivalent power (NEP) of this device is less than 10
^-17
W/Hz
^1/2
in the
1.5-5-\mu
spectral region.