A. Flusberg et Sf. Fulghum, DETECTIVITY OF SHOT-NOISE-LIMITED INTERFEROMETRIC SYSTEMS MEASURING WEAK GASEOUS ABSORPTION, Optical engineering, 35(6), 1996, pp. 1761-1771
Three alternative interferometric-calorimetry systems that can be used
to detect extremely small concentrations of trace gases are compared
for their sensitivity limits due to both shot noise and vibrational no
ise. The three systems are (1) a pulsed system based on excitation by
a repetitively pulsed heating laser; (2) a continuous-wave (cw) acoust
ic system, based on excitation by a cw heating laser whose intensity i
s modulated at an acoustic resonance frequency of the absorption cell;
and (3) a cw isobaric (optical homodyne) system, based on a cw heatin
g laser whose intensity is modulated at a frequency that is well below
the acoustic cutoff of the absorption cell. It is shown that the shot
-noise-limited sensitivities of the three systems are comparable, but
that the potential presence of vibrational noise strongly favors the p
ulsed system. (C) 1996 Society of Photo-Optical instrumentation Engine
ers.