Methods and systems for optical beam steering

Abstract

An integrated optical beam steering device includes a planar dielectric lens that collimates beams from different inputs in different directions within the lens plane. It also includes an output coupler, such as a grating or photonic crystal, that guides the collimated beams in different directions out of the lens plane. A switch matrix controls which input port is illuminated and hence the in-plane propagation direction of the collimated beam. And a tunable light source changes the wavelength to control the angle at which the collimated beam leaves the plane of the substrate. The device is very efficient, in part because the input port (and thus in-plane propagation direction) can be changed by actuating only log2 N of the N switches in the switch matrix. It can also be much simpler, smaller, and cheaper because it needs fewer control lines than a conventional optical phased array with the same resolution.

1 . An optical beam steering apparatus comprising:
 a substrate;   a slab waveguide formed on the substrate;   a planar lens, having a focal surface patterned in the slab waveguide, to direct light guided by the slab waveguide; and   an output coupler, formed on the substrate in optical communication with the slab waveguide, to couple at least a portion of the light out of a plane of the slab waveguide.   
     
     
         2 . The optical beam steering apparatus of  claim 1 , wherein the planar lens comprises a patterned layer of polysilicon disposed on a layer of silicon nitride. 
     
     
         3 . The optical beam steering apparatus of  claim 1 , wherein the planar lens is one of a Luneburg lens or a Rotman lens. 
     
     
         4 . The optical beam steering apparatus of  claim 1 , wherein the planar lens has a height that is adiabatically tapered to reduce loss at an interface between the planar lens and the slab waveguide. 
     
     
         5 . The optical beam steering apparatus of  claim 1 , wherein the output coupler comprises a curved grating. 
     
     
         6 . The optical beam steering apparatus of  claim 5 , wherein the curved grating has a curvature selected to collimate the light directed by the planar lens. 
     
     
         7 . The optical beam steering apparatus of  claim 5 , wherein the planar lens is configured to collimate the light guided by the slab waveguide. 
     
     
         8 . The optical beam steering apparatus of  claim 1 , wherein the output coupler comprises a two-dimensional photonic crystal coupler. 
     
     
         9 . The optical beam steering apparatus of  claim 1 , wherein the output coupler has a broken top-down mirror symmetry selected to couple the light out of the plane of the slab waveguide asymmetrically. 
     
     
         10 . The optical beam steering apparatus of  claim 1 , wherein the output coupler is configured to couple incident light into the plane of the slab waveguide and the planar lens is configured to couple the incident light into a mode guided by the slab waveguide. 
     
     
         11 . The optical beam steering apparatus of  claim 10 , further comprising:
 a detector, in optical communication with the slab waveguide, to detect the incident light in the mode guided by the slab waveguide.   
     
     
         12 . The optical beam steering apparatus of  claim 1 , further comprising:
 at least one optical amplifier, in optical communication with the slab waveguide, to amplify the light guided by the slab waveguide.   
     
     
         13 . The optical beam steering apparatus of  claim 12 , wherein the at least one optical amplifier comprises a slab-coupled optical waveguide amplifier integrated with the slab waveguide. 
     
     
         14 . The optical beam steering apparatus of  claim 12 , wherein the at least one optical amplifier comprises semiconductor optical amplifier switches. 
     
     
         15 . The optical beam steering apparatus of  claim 1 , further comprising:
 a passive splitter network, formed on the substrate in optical communication with the slab waveguide, to couple light into and/or out of the slab waveguide.   
     
     
         16 . The optical beam steering apparatus of  claim 1 , further comprising:
 a network of switches, formed on the substrate in optical communication with the slab waveguide, to couple light into and/or out of the slab waveguide.   
     
     
         17 . A system comprising:
 a seed laser to generate the light; and   an array of the optical beam steering apparatuses of  claim 1  tiled together and operably coupled to the seed laser.   
     
     
         18 . A method of optical beam steering, the method comprising:
 exciting an input to a planar lens with light guided by a slab waveguide;   directing the light within a plane of the slab waveguide with the planar lens; and   coupling the light out of the plane of the slab waveguide.   
     
     
         19 . The method of  claim 18 , wherein directing the light within plane of the slab waveguide with the planar lens comprises collimating the light. 
     
     
         20 . The method of  claim 18 , wherein coupling the light out of the plane of the slab waveguide comprises diffracting the light with a curved grating in optical communication with the planar lens.