Widely-tunable mid-infrared ring cavity pump-enhanced OPO and application in photo-thermal interferometric trace ethane detection

Jack W. Thomas*, Adam Polak, Gerald M. Bonner, David Logie, Malcolm H. Dunn, Jonathan C.F. Matthews, David J.M. Stothard

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

The development of a broadly and accurately tunable single-frequency mid-infrared laser source and its application to a sensitive laser absorption detection method are described. Photo-thermal interferometric spectroscopy is employed as a phase-sensitive method to detect the minute refractive index change caused by the heating of a gas under laser radiation. A separate probe beam allows for the spectrally-interesting mid-infrared region to be examined whilst utilizing low cost, high detectivity photodetectors in the visible/near-infrared region. We also describe the implementation of a Sagnac interferometer to minimize the effects of environmental perturbation and provide inherent passive stability. A continuous-wave ring-cavity pump-enhanced OPO has been developed to provide excitation light from 3–4 µm at 140 mW with the ability to mode-hop tune continuously over 90 cm−1 in 0.07 cm−1 steps. Complementary use of both detection apparatus and excitation source has allowed for presence of ethane to be detected down to 200 parts per billion.

Original languageEnglish
Pages (from-to)4550-4562
Number of pages13
JournalOptics Express
Volume28
Issue number4
DOIs
Publication statusPublished - 3 Feb 2020

Structured keywords

  • Bristol Quantum Information Institute

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