Mode transformation and loss reduction in silicon waveguide structures utilizing tapered transition regions
First Claim
1. An optical waveguiding structure comprisinga slab/strip single crystal silicon waveguide including a top major surface;
- a silicon rib waveguide disposed over a portion of the top major surface of the slab-strip single crystal silicon waveguide, the silicon rib waveguide defined as comprising an input face and an output face such that an optical signal propagating along the silicon slab/strip waveguide will be coupled through the silicon rib input face to thereafter propagate along both the slab/strip and the rib, and subsequently exit the silicon rib waveguide along the output face and then propagate along the slab/strip silicon waveguide; and
at least one silicon lensed taper disposed along a portion of the slab-strip waveguide top major surface so as to be contiguous with at least one of the silicon rib waveguide input face and output face, the silicon lensed taper used to improve optical coupling between the silicon slab/strip waveguide and the silicon rib waveguide.
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Abstract
A low loss coupling arrangement between a slab/strip waveguide and a rib waveguide in an optical waveguiding structure formed on a silicon-on-insulator (SOI) platform utilizes tapered sections at the input and/or output of the rib waveguide to reduce loss. Optical reflections are reduced by using silicon tapers (either vertical tapers, horizontal tapers, or two-dimensional tapers) that gradually transition the effective index seen by an optical signal propagating along the slab/strip waveguide and subsequently into and out of the rib waveguide. Loss can be further reduced by using adiabatically contoured silicon regions at the input and output of the rib waveguide to reduce mode mismatch between the slab/strip waveguide and rib waveguide. In a preferred embodiment, concatenated tapered and adiabatic sections can be used to provide for reduced optical reflection loss and reduced optical mode mismatch.
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Citations
37 Claims
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1. An optical waveguiding structure comprising
a slab/strip single crystal silicon waveguide including a top major surface; -
a silicon rib waveguide disposed over a portion of the top major surface of the slab-strip single crystal silicon waveguide, the silicon rib waveguide defined as comprising an input face and an output face such that an optical signal propagating along the silicon slab/strip waveguide will be coupled through the silicon rib input face to thereafter propagate along both the slab/strip and the rib, and subsequently exit the silicon rib waveguide along the output face and then propagate along the slab/strip silicon waveguide; and at least one silicon lensed taper disposed along a portion of the slab-strip waveguide top major surface so as to be contiguous with at least one of the silicon rib waveguide input face and output face, the silicon lensed taper used to improve optical coupling between the silicon slab/strip waveguide and the silicon rib waveguide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. An optical waveguiding structure providing both optical mode matching and optical reflection reduction, said structure comprising
a slab/strip single crystal silicon waveguide including a top major surface; -
a silicon rib waveguide disposed over a portion of the top major surface of the slab/strip single crystal silicon waveguide, the silicon rib waveguide defined as comprising an input face and an output face such that an optical signal propagating along the silicon slab/strip waveguide will be coupled through the silicon rib input face to thereafter propagate along both the slab/strip and the rib, and subsequently exit the silicon rib waveguide along the output face and then propagate along the slab/strip silicon waveguide; an adiabatically-contoured silicon region disposed along the slab/strip waveguide top major surface so as to be contiguous with either one of the silicon rib waveguide input face and output face, the adiabatically-contoured silicon region used to provide optical mode matching between the silicon slab/strip waveguide and the silicon rib waveguide; and a silicon lensed taper disposed along the slab/strip waveguide top major surface so as to be contiguous with an exposed endface of the adiabatically-contoured silicon region, the silicon taper providing a change in effective index between the silicon slab/strip waveguide and the silicon rib waveguide so as to reduce optical reflections at either one of the silicon rib waveguide input and output faces. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37)
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Specification