Expand this Topic clickable element to expand a topic
Skip to content
Optica Publishing Group

Use of etalon-immune distances to reduce the influence of background signals in frequency-modulation spectroscopy and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy

Not Accessible

Your library or personal account may give you access

Abstract

The detection sensitivity of phase-modulated techniques such as frequency-modulation spectroscopy (FMS) and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is often limited by etalon background signals. It has previously been shown that the impact of etalons can be reduced by the use of etalon-immune distances (EIDs), i.e., by separating the surfaces that give rise to etalons by a distance of q·Lm, where Lm is given by c/2nνm, where, in turn, n and νm are the index of refraction between the components that make up the etalon (thus most often that of air) and the modulation frequency, respectively, and where q is an integer (i.e., 1, 2, 3,…) or half-integer (i.e., 1/2, 1, 3/2,…) for the dispersion and absorption modes of detection, respectively. An etalon created by surfaces separated by an EID will evade detection and thereby not contribute to any background signal. The concept of EIDs in FMS and NICE-OHMS is in this work demonstrated, scrutinized, and discussed in some detail. It is shown that the influence of EIDs on the absorption and dispersion modes of detection is significantly different; signals detected at the dispersion phase are considerably less sensitive to deviations from exact EID conditions than those detected at the absorption phase. For example, the FM background signal from an etalon whose length deviates from an EID by 2.5% of Lm (e.g., by 1 cm for an Lm of 40 cm), detected in dispersion, is only 9% of that in absorption. This makes the former mode of detection the preferred one whenever a sturdy immunity against etalons is needed or when optical components with parallel surfaces (e.g., lenses, polarizers, or beam splitters) are used. The impact of the concept of EIDs on NICE-OHMS is demonstrated by the use of Allan–Werle plots.

© 2014 Optical Society of America

Full Article  |  PDF Article
More Like This
Wavelength-modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy signal line shapes in the Doppler limit

Aleksandra Foltynowicz, Weiguang Ma, Florian M. Schmidt, and Ove Axner
J. Opt. Soc. Am. B 26(7) 1384-1394 (2009)

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

Figures (8)

You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

Equations (13)

You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access Optica Member Subscription

Select as filters


Select Topics Cancel
© Copyright 2024 | Optica Publishing Group. All Rights Reserved