Sub-Doppler dispersion and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy revised
2008 (English)In: Journal of the Optical Society of America B, Vol. 25, no 7, 1166-1177 p.Article in journal (Refereed) Published
An expression for the peak-to-peak sub-Doppler optical phase shift of two counter-propagating modes of light, to which the noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) dispersion signal is proportional, valid for arbitrary degree of saturation, is derived.
For low degrees of saturation it agrees with the expression for weakly saturating (ws) conditions, [(1+S)-1/2-(1+2S)-1/2]α0/2, where S is the degree of saturation and α0 the unsaturated peak absorption.
However, the new expression, which can be written as 0.45S(1+S)-1α0/2, does not predict a distinct maximum as the ws-expression does; instead it predicts an optical phase shift that increases monotonically with S and levels off to 0.45α0/2 for large S. This alters the optimum conditions for the sub-Doppler NICE-OHMS technique and improves its shot-noise-limited detectability.
The new expression is based upon the same explicit assumptions as the ws-expression but not the Kramers-Kronig’s relations, which are not valid for nonlinear responses, and is supported by experimental results up to S = 100. The new expression is expected to be valid for all techniques measuring sub-Doppler dispersion signals
Place, publisher, year, edition, pages
2008. Vol. 25, no 7, 1166-1177 p.
line shapes and shifts, lasers, fiber, dispersion, spectroscopy, heterodyne, spectroscopy, modulation, spectroscopy, saturation
Atom and Molecular Physics and Optics Atom and Molecular Physics and Optics
IdentifiersURN: urn:nbn:se:umu:diva-9812DOI: 10.1364/JOSAB.25.001166OAI: oai:DiVA.org:umu-9812DiVA: diva2:149483