Multilayer Optical Phased Array for Low-Grating-Lobe Beam Steering
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Solution Overview
Problem
Existing optical phased arrays face challenges in achieving long antennas with a pitch smaller than half-wavelength, leading to grating lobes and phase errors, which reduce power in the main lobe and introduce false recordings.
Innovation Solution
An integrated optical structure with a slab waveguide configuration, where optical phased arrays are stacked across multiple layers, using coupling sections and a slab waveguide to steer optical beams in-plane before emission, minimizing grating lobes and phase errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the pitch of optical phased array antennas is reduced below half-wavelength to achieve smaller device size, then the area and volume of the device are reduced, but grating lobes appear which reduce power in the main lobe and cause false recordings
Solution Approach 1:
The patent transitions from planar 2D antenna arrangement to 3D stacked layers, allowing sub-half-wavelength pitch in the horizontal plane without grating lobes by utilizing the vertical dimension for layer separation. Multiple optical phased arrays are stacked vertically with each layer separated by distance greater than half-wavelength, enabling compact footprints while maintaining main lobe power.
Solution Approach 2:
The optical phased array is segmented into multiple independent layers, each containing a subset of antennas. This segmentation allows each layer to operate with sub-half-wavelength pitch without generating grating lobes, as the vertical separation between layers prevents the formation of grating lobe patterns that would otherwise occur in planar arrangements.
2Temperature
If waveguide antennas are made 1-2cm long to achieve sufficient directivity and reduce beam divergence, then beam divergence is reduced, but phase errors accumulate due to sidewall roughness
Solution Approach 1:
The patent uses vertical stacking to achieve the required 1-2cm antenna length equivalent in the vertical dimension rather than extending waveguides horizontally. This reduces the physical length of individual waveguides while maintaining the effective aperture needed for low beam divergence, thereby reducing phase errors from sidewall roughness.
Solution Approach 2:
Multiple shorter waveguide antennas across different layers are merged to form the effective long antenna structure. The combined radiation pattern of multiple short waveguides stacked vertically produces the same directivity as a single long waveguide, but with reduced phase errors since each individual waveguide is shorter.
3Object-generated harmful factors
If waveguide thickness is increased to reduce pitch and avoid coupling between neighboring antennas, then coupling is avoided, but TE/TM mode mixing occurs
Solution Approach 1:
The patent resolves the coupling problem by separating waveguides in the vertical dimension through stacking, rather than increasing waveguide thickness in the horizontal plane. This maintains the original waveguide dimensions that support single-mode operation while achieving the required pitch reduction through 3D arrangement.
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 configuration allows for a very small pitch without coupling between neighboring waveguides, maximizing power in the main lobe and reducing phase errors, enhancing beam steering capabilities.
Implementation Method 1
a slab waveguide formed on the substrate and between two of the optical layers... wherein the slab waveguide is in optical communication with the coupling sections
Implementation Method 2
an optical phased array comprising a plurality of optical waveguides; and a coupling section for each of the optical waveguides
Data Source
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AI summary
An integrated optical structure (1) for phase front engineering of optical beams (2) comprising: - a substrate (100); - a plurality of optical layers (201;202) formed on said substrate (100) and comprising: o an optical phased array (21;22) comprising a plurality of optical waveguides (220); and o a coupling section (20) for each of said optical waveguides (220) configured to control the phase of an optical beam (2) coupling out of said optical waveguide (220); and - a slab waveguide (300) formed between two of said optical layers (201;202) and in optical communication with said coupling sections (20) of said two optical layers (201;202); and wherein said slab waveguide (300) comprises a slab waveguide outcoupling structure (301) configured for transmission of optical beams (2) out of and/or for reception of optical beams (2) into the plane (7) of said substrate (100).