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Shot-noise-limited Doppler-broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry
Umeå University, Faculty of Science and Technology, Department of Physics. State Key Laboratory of Quantum Optics & Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, 030006 Taiyuan, China; Collaborative Innovation Center of Extreme Optics, Shanxi University, 030006 Taiyuan, China.ORCID iD: 0000-0002-3966-8943
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-6219-3296
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-8580-9700
2018 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 4, p. 715-718Article in journal (Refereed) Published
Abstract [en]

Shot-noise-limited Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) has been realized by implementation of balanced detection. A characterization of the system based on Allan-Werle plots of the absorption coefficient, retrieved by fitting a model function to data, shows that the system has a white noise equivalent absorption per unit length per square root of bandwidth of 2.3 x 10(-13) cm(-1) Hz(-1/2), solely 44% above the shot noise limit, and a detection sensitivity of 2.2 x 10(-14) cm(-1) over 200 s, both being unprecedented for Db NICE-OHMS. The white noise response follows the expected inverse square root dependence on power that is representative of a shot-noise-limited response, which confirms that the system is shot-noise-limited. 

Place, publisher, year, edition, pages
2018. Vol. 43, no 4, p. 715-718
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:umu:diva-145590DOI: 10.1364/OL.43.000715ISI: 000425123700023PubMedID: 29444060OAI: oai:DiVA.org:umu-145590DiVA, id: diva2:1191981
Funder
Swedish Research Council, 2015-04374Available from: 2018-03-21 Created: 2018-03-21 Last updated: 2018-11-06Bibliographically approved
In thesis
1. Mid- and near-infrared NICE-OHMS: techniques for ultra-sensitive detection of molecules in gas phase
Open this publication in new window or tab >>Mid- and near-infrared NICE-OHMS: techniques for ultra-sensitive detection of molecules in gas phase
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is a technique for ultra-sensitive detection of molecular absorption and dispersion. For highest performance, the technique combines cavity enhancement (CE) with frequency modulation (FM); while the former increases the effective interaction length between the light and the analyte by several orders of magnitudes, the latter removes the in-coupling of 1/f noise and makes the signals background free. The combination of CE and FM also gives the technique an immunity to amplitude noise caused by the jitter of the laser frequency relative to the cavity resonance frequencies. All these properties make the technique suitable for ultra sensitive trace gas detection in the sub-parts-per-trillion (ppt) range. The aim of this thesis is to improve the performance of the NICE-OHMS technique and to increase its range of applications.

The work in this thesis can be divided into three areas:Firstly, a mid-infrared (MIR)-NICE-OHMS instrumentation was developed. In a first realization an unprecedented white-noise equivalent absorption limit for Doppler broadened (Db) detection in the MIR of 3×10-9 cm-1Hz-1/2was demonstrated. This was subsequently improved to 2.4×10-10 cm-1Hz-1/2allowing for detection methane and its two main isotopologues (CH3D and 13CH4) at their natural abundance.Secondly, further development of an existing near-infrared NICE-OHMS system was performed. This resulted in an improved longtime stability and the first shot-noise limited NICE-OHMS system for Db detection with a noise equivalent absorption limit of 2.3×10-14 cm-1detected over 200 s. Thirdly, models and theoretical descriptions of NICE-OHMS signals under strong absorption conditions and from methane under high laser power were developed. It was experimentally verified that the models allow for a more accurate evaluation of NICE-OHMS signals under a wide range of conditions.

Abstract [sv]

Brusimmun kavitetsförstärkt optisk-heterodyndetekterad molekylärspektroskopi (eng.Noise-immune cavity-enhanced optical heterodyne molecular spectrometry, NICE-OHMS) är en teknik för ultrakänslig detektion av molekylär absorption och dispersion. NICE-OHMS-tekniken kombinerar kavitetsförstärkning (eng. CE) med frekvensmodulering (FM); emedan den första väsentligt ökar den effektiva interaktionslängden mellan ljuset och analyten vilket ökar teknikens känslighet, tar den senare bort inkopplingen av 1/f-brus och gör signalerna bakgrundsfria. Kombinationen av CE och FM ger också tekniken en immunitet mot amplitudstörning som orsakas av jitter hos laserljusets frekvens i förhållande till kavitetsresonansfrekvenserna. Alla dessa egenskaper gör tekniken lämplig för ultrakänslig spårgasdetektering i och under ppt (eng. parts-per-trillion) - området. Syftet med denna avhandling är att förbättra prestandan hos NICE-OHMS-tekniken och att öka dess tillämpningspotential.

Avhandlingen kan delas in i tre delar: Inom den första utvecklades en mid-infraröd (MIR)-NICE-OHMS instrumentering. Vid en första realisering påvisades en aldrig tidigare uppnådd vitt-brus-ekvivalent absorptionsgräns för Dopplerbreddad (Db) detektering i MIR området på 3 × 10-9 cm-1Hz-1/2. Detta förbättrades därefter till 2,4 x 10-10 cm-1Hz-1/2, vilket möjliggör detektering av metan och dess två huvudsakliga isotopologer (CH3D och 13CH4) vid deras naturliga förekomst. Inom det andra området utfördes vidareutveckling av ett existerande NICE-OHMS-system verksamt i det när-infraröda (NIR) området. Detta resulterade i en förbättrad långtidsstabilitet och en brus-ekvivalent absorptionsgräns för Db detektion på 2,3 × 10-14 cm-1 mätt över 200 s. Inom den tredje utvecklades modeller och teoretiska beskrivningar av NICE-OHMS under starka absorptionsförhållanden och från metan under hög laserintensitet. Det var experimentellt verifierat att modellerna möjliggör en mer noggrann utvärdering av NICE-OHMS-signalerunder ett stort antal förhållanden.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2018. p. 139
Keywords
spectrometry, NICE-OHMS, trace gas detection, acetylene, methane, isotopologues, near-infrared, mid-infrared, shot-noise, optical parametric oscillator
National Category
Atom and Molecular Physics and Optics
Research subject
engineering science with specialization in microsystems technology
Identifiers
urn:nbn:se:umu:diva-153068 (URN)978-91-7601-977-1 (ISBN)
Public defence
2018-11-30, N450, Naturvetarhuset, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2018-11-09 Created: 2018-11-06 Last updated: 2018-11-13Bibliographically approved

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Zhao, GangHausmaninger, ThomasMa, WeiguangAxner, Ove

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