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Wide shoulder, high order mode filter for thick-silicon waveguides

  • US 10,295,746 B2
  • Filed: 08/28/2018
  • Issued: 05/21/2019
  • Est. Priority Date: 03/07/2014
  • Status: Active Grant
First Claim
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1. An optical filter for attenuating higher-order transverse modes, the optical filter comprising:

  • a shoulder slab, wherein;

    the shoulder slab is formed of a first material having a first index of refraction and is disposed atop a second material having a second index of refraction, the first index of refraction being higher than the second index of refraction; and

    a waveguide ridge disposed atop the shoulder slab, wherein;

    the waveguide ridge is formed of the first material;

    the waveguide ridge forms an input width in a first waveguide section along a direction of beam propagation, wherein;

    a first filter section, formed by the shoulder slab and the waveguide ridge in the first waveguide section, is capable of guiding light of a fundamental mode and the higher-order transverse modes along the direction of beam propagation; and

    the waveguide ridge tapers adiabatically inward from the input width to a reduced width, in a second waveguide section that adjoins the first waveguide section along the direction of beam propagation, wherein;

    a second filter section, formed by the shoulder slab and the tapering waveguide ridge in the second waveguide section, is capable of guiding the fundamental mode, wherein the higher-order transverse modes are pushed into the shoulder slab where they are less strongly guided than the fundamental mode,such that a proportion of energy guided in the fundamental mode, to energy guided in the higher-order transverse modes, increases along the direction of beam propagation in the second filter section.

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