A Vernier spectrometer is built with a near-infrared mode-locked Er:doped fiber laser, a Fabry-Perot cavity with finesse of 1000, a diffraction grating and a photo detector. The optical cavity provides high sensitivity in absorption detection by enhancing the interaction length of the light with molecular species contained in the cavity. Coupling an optical frequency comb to the cavity provided a broadband spectral bandwidth with high precision to measure the absorption of several molecular species simultaneously. Also, by using the optical cavity as a filter, transmission of some bunch comb lines was achieved. This comb filtering together with a simple grating and a photodiode formed the Vernier detection technique to provide very fast measurements while it kept the setup very simple and compact. The system allows to detect carbon dioxide in the air and water vapor and OH radicals in the flame in a spectrum spanning from 1550 nm to 1590 nm, approximately. The retrieved spectrum has a resolution of 9.3 GHz being acquired in 0.05 s.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:umu-132520 |
| Date | January 2017 |
| Creators | Fakhri, Maryam |
| Publisher | Umeå universitet, Institutionen för fysik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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