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Waveguide Polarizer Using Localized Surface Plasmons.

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Patent Application, Filed 20 Dec 91,

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Surface plasmon resonance in small particles of metal is employed to polarize light propagating in a waveguide. An ion-exchanged glass waveguide is provided with a 50 Angstrom 5 nm mass thick layer of silver which is deposited on the waveguide. The ion-exchanged glass waveguide having the specified layer of silver is annealed at 2000 C for 1 minute causing the silver film to bead, much like water droplets on a waxed car. The silver microparticles have a nonspherical shape with their major axes parallel to the surface of the waveguide and their minor axis perpendicular to the surface of the waveguide. When light from a HeNe laser at a wavelength of 633 nm is prism-coupled into the waveguide with the field of laser beam parallel to the major axes of the spheroids TE polarization the laser light is strongly absorbed and the TM light is passed. By orienting the microparticles with the major axes perpendicular to surface TM light will be absorbed and TE light will pass. Thus, changing the orientation of the nonspherical particles by 90 degrees changes the polarization state absorbed. The microparticles can be placed in the core of the waveguide, in the cladding, or on the cladding. All that is required of the microparticle location is that the electromagnetic field propagating in the waveguide extend to where the particles are located. The waveguide material is not limited to planar glass waveguides. Especially attractive are waveguide material of optical fibers and III-V semiconductor compounds. For optical fibers waveguide material the particles can be deposited directly onto the cladding or part of the cladding can be removed before deposition of the particles.

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  • Optics

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