QUANTUM-NOISE-LIMITED CAVITY RING-DOWN SPECTROSCOPY IN THE MID-INFRARED

Fleisher, Adam J.

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https://hdl.handle.net/2142/79390 Copy

Description

Title

QUANTUM-NOISE-LIMITED CAVITY RING-DOWN SPECTROSCOPY IN THE MID-INFRARED

Author(s)

Fleisher, Adam J.

Contributor(s)

• Hodges, Joseph
• Liu, Qingnan
• Long, David A.

Issue Date

24-Jun-15

Keyword(s)

Mini-symposium: High-Precision Spectroscopy

Abstract

We report a highly sensitive mid-infrared spectrometer capable of recording cavity ring-down events in the quantum (shot) noise limit. A linear optical cavity of finesse 31,000 was pumped by a distributed feedback quantum cascade laser (DFB-QCL) operating at 4.5 $mu$m until a cavity transmission threshold was reached. A fast optical switch then extinguished optical pumping and initiated a cavity decay which exhibited root-mean-square noise proportional to the square root of optical power (quantum noise) for several cavity time constants until a detector noise floor was reached. This spectrometer has achieved a noise-equivalent absorption of NEA = $2.6times10^{-11}$ wn Hz$^{-1/2}$ and a minimum absorption coefficient of $alpha = 2.3times10^{-11}$ wn in 3 seconds. Applications for such a highly sensitive spectrometer operating in the mid-infrared region, including ultra-trace molecular spectroscopy of chem{CO_2} isotopologues and the direct interrogation of weak mirror birefringence and polarization-dependent losses, will be discussed.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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http://hdl.handle.net/2142/79390

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