Low loss electrodes for electro-optic modulators

Abstract

An electro-optic modulator includes a substrate, at least two parallel optical waveguides, at least one ground plane, at least one active electrode with at least two lower portions of the active electrode, and an upper portion connected to the lower portions, the lower portions spaced apart from each other, each of the two lower portions of the active electrode extending over one of the optical waveguides. An electro-optic phase modulator has at least one optical waveguide and at least one active electrode formed on a face of the substrate, the active electrode having a wider upper portion and a narrower lower portion, the lower portions of the active electrode aligned with and extending over one of the optical waveguides. A bridge electrode has at least one narrower lower portion, and a wider upper portion, the lower portion for being arranged over an optical waveguide formed in a substrate.

1 . An electro-optic modulator comprising: 
 a substrate having at least one optical waveguide formed on a first face of the substrate;    at least one active electrode formed on the first face of the substrate aligned over the optical waveguide;    the active electrode having at least one narrower lower portion and wider upper portion,    the active electrode having a height that is at least 5 times as large as the width of the lower portion,    the active electrode operating to induce a refractive index change in the optical waveguide.    
   
   
       2 . The electro-optic modulator of  claim 1 , the upper portion having a width and height sufficient to match velocities of a signal in the optical waveguide and of an RF signal in the active electrode.  
   
   
       3 . The electro-optic modulator of  claim 1 , wherein the width of the upper portion is at least twice as great as the width of the lower portion.  
   
   
       4 . The electro-optic modulator of  claim 1 , wherein the width of the upper portion is at least three times as great as the width of the lower portion.  
   
   
       5 . The electro-optic modulator of  claim 1 , wherein the width of the upper portion is at least four times as great as the width of the lower portion.  
   
   
       6 . The electro-optic modulator of  claim 1 , wherein the width of the lower portion is about eight microns.  
   
   
       7 . The electro-optic modulator according to  claim 1 , further comprising: 
 at least one ground plane formed on the first face of the substrate spaced apart from the active electrode.    
   
   
       8 . The electro-optic modulator according to  claim 1 , further comprising: 
 ground planes formed on opposite sides of the active electrode, spaced apart from the active electrode.    
   
   
       9 . The electro-optic modulator according to  claim 8 , wherein the ground plane does not overlie the optical waveguide in an active region of the modulator.  
   
   
       10 . The electro-optic modulator according to  claim 1 , further comprising an insulator element arranged on either side of the lower portion to support the upper portion.  
   
   
       11 . The modulator according to  claim 1 , the lower narrower portion of the active electrode formed by depositing a first layer of metallization on the substrate, the upper wider portion of the active electrode formed by depositing at least a second layer of metallization over the first layer.  
   
   
       12 . The modulator according to  claim 11 , the upper wider portion of the active electrode being formed by depositing a third layer over the second layer in active regions of the modulator, but no third layer in bend regions of the modulator.