Optical Beam Steering Using Planar Dielectric Lens and Photonic Crystal
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Solution Overview
Problem
Current chip-scale optical phased arrays for LIDAR suffer from significant grating lobes due to the spacing requirements of dielectric waveguides, limiting their ability to achieve wide-angle steering and large power-aperture designs, unlike their RF counterparts which can utilize closely spaced metallic waveguides.
Innovation Solution
The use of a planar dielectric lens and a 2D photonic crystal output coupler in an optical beam steering apparatus, which allows for wide-angle steering by collimating and diffracting light beams, enabling the suppression of sidelobes and reducing power consumption through passive beamforming and overlapped subarrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If dielectric waveguides are spaced at several wavelengths to prevent excessive coupling, then coupling between waveguides is reduced, but grating lobes are significantly increased
Solution Approach 1:
The patent divides the optical beam steering function into two separate components: a phased array of dielectric waveguides for beam steering control, and a metallic waveguide layer for efficient power distribution. This segmentation allows each layer to be optimized independently - the dielectric layer for low coupling and the metallic layer for low loss transmission.
Solution Approach 2:
The patent introduces an intermediary coupling structure between the dielectric waveguides and metallic waveguides that enables efficient power transfer while maintaining the spacing benefits of dielectric waveguides. This intermediary layer acts as a bridge that combines the advantages of both dielectric and metallic waveguide systems.
2Ease of manufacture
If dielectric waveguides are used in optical phased arrays, then integration with photonic circuits is improved, but the spacing requirements lead to significant grating lobes that limit wide-angle steering
Solution Approach 1:
The patent segments the waveguide system into dielectric waveguides integrated with photonic circuits for beam steering, and separate metallic waveguides for power distribution. This allows the dielectric waveguides to be closely integrated with photonic circuits while the metallic waveguides provide the low-loss transmission path needed for wide-angle steering.
Solution Approach 2:
The patent creates a composite waveguide system combining dielectric and metallic materials, each performing their optimal function. The dielectric portion provides integration with photonic circuits and phase control, while the metallic portion provides low-loss power distribution across the aperture.
3Ease of manufacture
If RF phased array architectures are directly translated to optical domain, then component availability is improved, but the lack of closely spaced waveguide support in dielectrics results in significant grating lobes
Solution Approach 1:
The patent introduces a metallic waveguide intermediary layer that enables closely spaced waveguide configurations similar to RF phased arrays, while the dielectric waveguide layer maintains compatibility with photonic circuit fabrication processes. This intermediary metallic layer allows the system to achieve RF-like performance in the optical domain.
Solution Approach 2:
The patent changes the material parameter from purely dielectric to a hybrid dielectric-metallic structure, fundamentally altering the spacing characteristics. This parameter change enables sub-wavelength spacing similar to RF systems while maintaining optical domain operation and photonic circuit compatibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient wide-angle steering with reduced power dissipation and sidelobe suppression, allowing for a non-mechanical LIDAR system with high resolution and small size, while maintaining low power consumption and cost.
Implementation Method 1
the planar dielectric lens collimates light emitted by the first waveguide as a first collimated beam propagating in a first direction in a plane of the substrate and collimates light emitted by the second waveguide as a second collimated beam propagating in a second direction
Implementation Method 2
an output coupler formed on the substrate in optical communication with the planar dielectric lens... guides the first collimated beam in the first direction and the second collimated beam in the second direction and couples at least a portion of the first collimated beam and the second collimated beam out of the plane of the substrate
Data Source
AI summary
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.