Polarization-Independent Switch with Coupler Spacing Optimized for Low Voltage Operation.
Patent, Filed 12 Dec 83, patented 23 Jun 87,
DEPARTMENT OF THE NAVY WASHINGTON DC
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A process of fabricating an optical directional coupler switch for the TE- and TM-mode polarizations at a given wavelength. Initially, a trial set of waveguide fabrication parameters is used to fabricate a series of channel waveguide directional couplers having the same waveguide spacing and differing interaction lengths. The step is repeated for other waveguide spacings. The power splitting ratio of each directional coupler so fabricated is determined for guided light of one of the polarizations at the given wavelength. For each series of directional couplers having a respective common waveguide spacing, the arctangent of the square root of the power splitting ratio versus the interaction length is graphed and the coupling coefficient for the one polarization is found from the graph slope. The log of the coupling coefficients so determined is graphed versus the corresponding waveguide spacings. The previous three steps are repeated for guided light of the other polarization at the given wavelength. The set of waveguide fabrication parameters is varied and all the steps repeated until the desired set of parameters is arrived at for which the graphs of the log of the coupling coefficients versus the corresponding waveguide spacings for guided light of both polarization at the given wavelength coincide. Author
- Fiber Optics and Integrated Optics