We are using a correlated photon technique to
measures the absolute radiance of an IR source
by comparison to fundamental constants. This system starts with a
down-conversion setup designed to produce visible-IR photon pairs.
The IR source output beam to be measured is superimposed onto the IR
correlated photon output. By overlapping the two beams, spatially and
spectrally, the IR source effectively stimulates the production of
down-converted photons along that direction as well as along the
correlated visible photon direction. The enhancement is measured
along the visible direction with a visible detector. The ratio of the
visible down-converted signal with the IR beam on versus IR beam off
provides an absolute determination of the IR radiance.
Figure 1: Schematic of the absolute IR radiance setup
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