VERSATILE FILTER-MULTIPLEXERS FOR INTEGRATED OPTICS
Abstract
The feasibility of applying phase reversal and tapering techniques simultaneously to co-directional couplers is demonstrated and studied within a generalized framework. For two-section devices, switching diagrams are presented for tapers of the Hamming, raised-cosine, and Blackman class. The filtering-multiplexing characteristics for this class of device are comprehensively described by the compilation of a set of pertinent curves. Based on these a strategy to obtain the greatest advantages from a combination of the techniques is proposed. A general technique whereby modulation and multiplexing functions can be performed by a single device is discussed. Since the filter response of the aforementioned devices depends on the dispersive behavior of the coupled guides, a comprehensive study of basic optical guides is also conducted. Coefficients that describe the relative contribution to total guide dispersion from each section of the waveguide structure are introduced. These are cast in terms of normalized waveguide parameters which allows plotting of universal curves. This formalism now permits control of guide dispersion to be effected in a precise manner. A study of dispersive properties for the above family of device is also made in un-normalized form for a specific coupler type, those formed from Ti-diffused guides in LiNbO(,3). Special attention is given to accounting for all sources of dispersion, particularly the diffused-film region. An expression for the coupling coefficient, within the coupled-mode formalism, is derived for nonidentical nearly degenerate guides. Also, the effects of fabrication errors and overlays on device performance is addressed. A series of curves that generally characterize the basic and normalized coupler parameters is presented. These greatly facilitate proper device design and indicate parameter ranges where errors are minimal.
Degree
Ph.D.
Subject Area
Electrical engineering
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