Static Fourier transform spectrometers and laser wavelength meters
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This thesis reports the development of novel static Fourier transform spectrometers based upon Wallaston prisms and compact detector arrays. The path difference between orthogonal polarisation states of the input light varies smoothly across the aperture of the prism forming an interferogram in the spatial, rather than temporal, domain that is recorded with the detector array. A Fourier trans¬ form of this interferogram gives the spectral distribution of the incident light. The elimination of moving parts from the design makes the recorded interferogram inherently stable. I have developed an improved spectrometer utilising Wallaston prisms fabricated from materials of opposite sign birefringence. This new instrument has a significantly increased field of view compared with previous Wollaston prism based spectrometers. Additionally my work has involved the construction and evaluation of spectrometers for operation in the ultraviolet, visible and infrared regions of the spectrum. These spectrometers have been applied to the analysis of gasolines. Important properties such as gasoline brand and octane number have been identified from ultraviolet and near-infrared spectra using principal component analysis. Finally, I adapted the spectrometer design to make a fibre-coupled laser wavelength meter based on a modified Wollaston prism. For a narrow linewidth source a fringe period measurement technique, used as an alternative to the Fourier transform algorithm, obtains precision measurement (1 part in 10^6) of the centre wavelength. The wavelength meter and spectrometers have numerous applications in the held of general laboratory instrumentation and their robust, compact nature makes them particularly suitable where held based operation is required.
Thesis, PhD Doctor of Philosopy
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