Phase locking in laser arrays.
Item
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Title
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Phase locking in laser arrays.
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Identifier
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AAI9530931
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identifier
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9530931
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Creator
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Xu, Jingwen.
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Contributor
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Adviser: Ying-chih Chen
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Date
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1995
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Optics | Physics, General
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Abstract
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A two-element laser array is used as a simple experimental model for studying the physics of phase locking in evanescent-coupled laser arrays. The array consists of two closely-spaced lasing filaments created in a monolithic Nd:YAG etalon by photo-pumping. With photo-pumping, the key parameters of the laser array can be controlled and continuously varied for exploring the various phenomena of phase locking over a wide range of coupling strength for comparison with previous theoretical calculations. The study revealed discrepancies between the experimental results and previous theoretical predictions based on the coupled-oscillator model. These discrepancies include: (1) Contrary to previous predictions of slow locking process and the existence of instability, the time of phase locking is observed to be as fast as the lasing process without a slow evolutionary process. There is also no optical instability in the presence of a frequency detuning between the two elements. (2) The experimentally measured frequency detuning for phase locking is much larger than the theoretical predictions. There exists a complex modal patterns in the vicinity of the boundary of phase locking which can not be synthesized by the coupled-oscillator model. The fast locking and lack of instability can be attributed to the presence of a large imaginary part of the coupling strength not properly taking into account in previous theoretical modeling. However, the range of phase locking and the complex transitional behavior can not be explained by the coupled-oscillator model. Our analysis shows that a two-element laser array is not a two-mode system, but can posses numerous eigenmodes, each having a different frequency. For a given frequency, the resonance condition in each branch determines the field strength in that branch and the modal pattern for the composite waveguide can be calculated numerically. The lasing mode is the one with the highest modal gain. With this new understanding, we have successfully explained the complex modal patterns in the vicinity of the transition region and the magnitude of frequency detuning tolerance for phase locking. Another important implication of our new understanding is that the temporal behavior of the laser array can not be synthesized by the linear superposition of the temporal behavior of the individual elements because the dynamics in the laser array is not a deterministic process.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
