dc.contributor.author Chen, Xiaopei en_US dc.date.accessioned 2011-08-22T18:53:36Z dc.date.available 2011-08-22T18:53:36Z dc.date.issued 2003-09-08 en_US dc.identifier.other etd-07202006-001939 en_US dc.identifier.uri http://hdl.handle.net/10919/11124 dc.description.abstract In this report, we give a deeper investigation of the loss-compensated recirculating delayed self-heterodyne interferometer (LC-RDSHI) for ultra-narrow linewidth measurement, including the theoretical analysis, experimental implementation, further modification on the system and more applications. Recently, less than 1kHz linewidth fiber lasers have been commercialized. But even the manufacturers face a challenge on accurately measuring the linewidth of such lasers. There is a need to develop more accurate methods to characterize ultra-narrow laser linewidth and frequency noises. Compared with other currently available linewidth measurement techniques, the loss-compensated recirculating delayed-heterodyne interferometer (LC-RDSHI) technique is the most promising one. It overcomes the bottle-neck of the high resolution requirement on the delayed self-heterodyne interferometer (DSHI) by using a short length of fiber delay line. This method does not need another narrower and more stable laser as the reference which is the necessary component in heterodyne detection. The laser spectral lineshape can be observed directly instead of complicated interpretation in frequency discriminator techniques. The theoretical analysis of a LC-RDSHI gives us a guidance on choosing the optimal parameters of the system and assists us to interpret the recorded spectral lineshape. Laser linewidth as narrow as 700Hz has been proved to be measurable by using the LC-RDSHI method. The non-linear curve fitting of Voigt lineshape to separate Lorentzian and Gaussian components was investigated. Voigt curve fitting results give us a clear view on laser frequency noises and laser linewidth nature. It is also shown that for a ultra-narrow linewidth laser, simply taking 20dB down from the maximum value of the beat spectrum and dividing by $2\sqrt{99}$ will over estimate the laser linewidth and coherent length. Besides laser linewidth measurement in the frequency domain, we also implemented time-domain frequency noise measurement by using a LC-RDSHI. The long fiber delay obtained by a fiber recirculating loop provides a higher resolution of frequency noise measurement. However, spectral width broadening due to fiber nonlinearity, environmental perturbations and laser intrinsic 1/f frequency noises are still potential problems in the LC-RDSHI method. A new method by adding a transmitter switch and a loop switch is proposed to minimize the Kerr effect caused by multiple recirculation. en_US dc.format.medium ETD en_US dc.publisher Virginia Tech en_US dc.relation.haspart Dissertation_Xiaopei.pdf en_US dc.rights This Item is protected by copyright and/or related rights. Some uses of this Item may be deemed fair and permitted by law even without permission from the rights holder(s), or the rights holder(s) may have licensed the work for use under certain conditions. For other uses you need to obtain permission from the rights holder(s). en_US dc.subject Ultra-narrow linewidth laser en_US dc.subject heterodyne detection en_US dc.subject Lorentzian linewidth en_US dc.title Ultra-Narrow Laser Linewidth Measurement en_US dc.type Dissertation en_US dc.contributor.department Electrical and Computer Engineering en_US dc.description.degree Ph. D. en_US thesis.degree.name Ph. D. en_US thesis.degree.level doctoral en_US thesis.degree.grantor Virginia Polytechnic Institute and State University en_US thesis.degree.discipline Electrical and Computer Engineering en_US dc.contributor.committeechair Wang, Anbo en_US dc.contributor.committeemember Xu, Yong en_US dc.contributor.committeemember Pickrell, Gary R. en_US dc.contributor.committeemember Jacobs, Ira en_US dc.contributor.committeemember Heflin, James R. en_US dc.identifier.sourceurl http://scholar.lib.vt.edu/theses/available/etd-07202006-001939 en_US dc.date.sdate 2006-07-20 en_US dc.date.rdate 2006-10-30 dc.date.adate 2006-10-30 en_US
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