Doppler broadened NICE-OHMS beyond the triplet formalism: assessment of optimum modulation index

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Ehlers, Patrick,1981-Umeå universitet,Institutionen för fysik,Laser physics group (author)

Doppler broadened NICE-OHMS beyond the triplet formalism : assessment of optimum modulation index

Ingår i Patrick Ehlers doktorsavhandling som delarbete nr XI med titeln: NICE-OHMS beyond the triplet formalism: assessment of the optimum modulation index.
The dependence of Doppler broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) on the modulation index, beta, has been investigated experimentally on C2H2 and CO2, both in the absence and the presence of optical saturation. It is shown that the maximum signals are obtained for beta that produce more than one pair of sidebands: in the Doppler limit and for the prevailing conditions (unsaturated transition and the pertinent modulation frequency and Doppler widths) around 1 and 1.4 for the dispersion and absorption detection phases, respectively. The results verify predictions given in an accompanying work. It is also shown that there is no substantial broadening of the NICE-OHMS signal for beta < 1. The use of beta of unity has yielded a Db-NICE-OHMS detection sensitivity of 4.9 x 10(-12) cm(-1) Hz(-1/2), which is the lowest (best) value so far achieved for NICE-OHMS based on a tunable laser. The number of sidebands that needs to be included in fits of the line-shape function to obtain good accuracy has been assessed. It is concluded that it is enough to consider three pairs of sidebands whenever the systematic errors in a concentration assessment should be below 1% when beta < 2 are used and <1 parts per thousand for beta < 1.5.

Wang, JunyangUmeå universitet,Institutionen för fysik(Swepub:umu)juwa0004 (author)
Silander, Isak,1980-Umeå universitet,Institutionen för fysik(Swepub:umu)issi0002 (author)
Axner, Ove,1957-Umeå universitet,Institutionen för fysik(Swepub:umu)ovax0001 (author)
Umeå universitetInstitutionen för fysik (creator_code:org_t)

In:Journal of the Optical Society of America. B, Optical physics: Optical Society of America31:7, s. 1499-15070740-32241520-8540

By the author/editor: Ehlers, Patrick, ...; Wang, Junyang; Silander, Isak, ...; Axner, Ove, 1957 ...

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NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Atom and Molecul ...

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