Integrated on-chip polarizer

Abstract

A low loss high extinction ratio on-chip polarizer is disclosed. The polarizer includes an input waveguide taper having an outer waveguiding region that widens in the direction of light propagation along at least a portion of the taper length, and a core waveguiding region that narrows in the direction of light propagation along at least a portion of the taper length, so as to selectively squeeze out light of undesired modes into the outer regions while preserving light of a desired mode in the waveguide core. An integrated light absorber/deflector may be coupled to the outer waveguiding regions.

1 - 39 . (canceled) 
     
     
         40 . A waveguide mode filter comprising:
 a bi-layer waveguide comprising a first end for connecting to an input waveguide and a second end for connecting to an output waveguide, the input waveguide configured to support a first mode and a second mode;   wherein the bi-layer waveguide comprises a first waveguide layer positioned over a second waveguide layer of a greater width, wherein the first waveguide layer tapers toward a middle portion of the bi-layer waveguide to selectively squeeze out light of the second mode into the second waveguide layer while allowing light of the first mode to propagate in the first waveguide layer to the second end.   
     
     
         41 . The waveguide mode filter of  claim 40  wherein the second waveguide layer tapers down toward at least one of the first end or the second end. 
     
     
         42 . The waveguide mode filter of  claim 40  wherein the second waveguide layer tapers down toward the first and the second end. 
     
     
         43 . The waveguide mode filter of  claim 40  comprising a light attenuator or deflector configured to prevent the light of the second mode to couple back into the first waveguide layer at the second end. 
     
     
         44 . The waveguide mode filter of  claim 40  comprising a light absorber configured to selectively absorb light propagating in the second waveguide layer. 
     
     
         45 . The waveguide mode filter of  claim 44  wherein the light absorber comprises one of: a metal layer coupled to the second waveguide layer, a layer of light-absorbing semiconductor material coupled to the second waveguide layer, or a region of the second waveguide layer configured to absorb or deflect light propagating in the second waveguide layer. 
     
     
         46 . The waveguide mode filter of  claim 40  comprising a light deflector configured to selectively re-direct light propagating in the second waveguide layer away from the output waveguide. 
     
     
         47 . The waveguide mode filter of  claim 46  wherein the light deflector comprises one of: an optical grating formed in the second waveguide layer or optically coupled therewith, or an auxiliary waveguiding layer optically coupled to the second waveguide layer so as to re-direct light propagating therein away from the first waveguide layer. 
     
     
         48 . The waveguide mode filter of  claim 40 , wherein the first mode is characterized by a greater effective refractive index in the bi-layer waveguide than the second mode. 
     
     
         49 . The waveguide mode filter of  claim 40 , wherein the first mode is a TE0 mode and the second mode is one of: a TM mode, or a higher-order TE mode. 
     
     
         50 . The waveguide mode filter of  claim 40 , wherein the first waveguide layer and the second waveguide layer are formed by selectively etching a layer of semiconductor or dielectric material to different heights. 
     
     
         51 . The waveguide mode filter of  claim 40  wherein the first waveguide layer has a same width at the first end and the second end. 
     
     
         52 . The waveguide mode filter of  claim 40  wherein the first waveguide layer and the second waveguide layer form a strip-loaded waveguide disposed over a support substrate. 
     
     
         53 . The waveguide mode filter of  claim 40  wherein the first waveguide layer and the second waveguide layer are defined in a silicon layer of a silicon-on-isolator chip.