Gas refractometry using hollow core photonic bandgap fiber
Loading...
URL
Journal Title
Journal ISSN
Volume Title
Sähkötekniikan korkeakoulu |
Master's thesis
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Authors
Date
2015-03-30
Department
Major/Subject
Optoelectronics and Photonics
Mcode
ELEC004Z
Degree programme
EST - Master’s Programme in Micro and Nanotechnology
Language
en
Pages
48 + 6
Series
Abstract
Over the last two decades, much research has been carried out on sensors based on photonic crystal fibers. Their unique structure comprising of a periodic array of air holes running along their length provides optical properties that are highly suited for refractometer sensors. The thesis presents a fiber-optic interferometric gas refractometer which is capable of spectrally resolved measurements of both real and imaginary parts of the complex refractive index. The refractometer is based on an earlier fiber based Mach-Zehnder-type refractometer design that was used to determine the refractive index of air-acetylene mixture. The aim of the thesis was to improve the device design in order to ascertain the refractive index of pure acetylene. The device adopts a hollow-core photonic bandgap fiber as both a sample cell and a waveguide. This provides the best overlap between probing light and the analyte. In addition, it requires a very small volume of the analyte due to the small dimensions of the fiber, and the sample cell can be made long while keeping the device compact. The complex refractive index of approx. 96 percent pure acetylene was measured within the optical C band where the gas has a number of pronounced resonance frequencies. The measurement was repeated in approx. 500 Pa air and was used as reference for interpreting the results for acetylene. The optical absorption and refractive index change of acetylene over the resonance frequencies were analyzed and its absorption coefficient and refractive index were calculated. The demonstrated capability of this device to measure the real and imaginary parts of the refractive index of an analyte has important implications in the sensor industry.Description
Supervisor
Ludvigsen, HanneThesis advisor
Shavrin, IgorKeywords
gas refractometer, hollow core photonic bandgap fiber, Mach-Zehnder interferometer, complex refractive index, fiber sensor