Optical Phased Array Evanescent Coupling Scaling
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Solution Overview
Problem
Current optical phased arrays face challenges in scaling up due to the short optical wavelength, which requires precise phase and power balancing of thousands of nanoantennas to form coherent far-field radiation patterns, limiting their functionality to small-scale implementations with constrained functionalities like beam focusing and steering.
Innovation Solution
A large-scale, two-dimensional optical phased array with densely integrated optical nanoantennas on a silicon chip, utilizing evanescently coupled waveguides and phase shifters, allows for precise control of optical power and phase distribution across a 64×64 element array, enabling the generation of arbitrary far-field radiation patterns through CMOS integration and active phase tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical phased arrays are scaled up to large-scale implementations, then the resolution and functionality of far-field radiation patterns are improved, but the manufacturing precision requirements become excessively stringent due to the short optical wavelength
Solution Approach 1:
The patent introduces waveguides as intermediary structures that couple evanescently to the antenna elements. These waveguides serve as mediators that can be fabricated with relaxed precision tolerances compared to directly fabricating thousands of precisely-spaced antenna elements, thereby reducing the overall manufacturing precision requirements while maintaining large-scale array functionality
Solution Approach 2:
The large-scale antenna array is segmented into multiple groups, with each group coupled to a separate waveguide. This segmentation allows independent fabrication and assembly of smaller sub-arrays, each with less stringent precision requirements, while still achieving the desired large-scale radiation pattern resolution when all segments are combined
2Adaptability or versatility
If the number of antenna elements is increased to enable arbitrary radiation patterns, then the versatility of the optical phased array is improved, but the device complexity and fabrication cost increase significantly
Solution Approach 1:
The waveguide-antenna element coupling structure is designed as a universal building block that can be replicated and tiled to create arrays of any size and configuration. This modular universal unit enables the system to achieve arbitrary radiation patterns through software control of the waveguide excitations without requiring different hardware configurations, thereby maintaining versatility while managing complexity
Solution Approach 2:
The patent employs a hierarchical nested structure where multiple antenna elements are nested along each waveguide, and multiple waveguides are nested within the overall array architecture. This nesting allows a large number of antenna elements to be organized in a compact, manageable structure that reduces interconnection complexity while enabling arbitrary radiation pattern formation through coordinated control of the nested waveguide-antenna subsystems
3Ease of manufacture
If traditional fabrication methods are used for optical phased arrays, then the manufacturing process is simple, but the scalability to large-scale two-dimensional arrays is limited
Solution Approach 1:
The patent replaces direct mechanical/fabrication precision requirements for positioning thousands of antenna elements with an optical evanescent coupling mechanism. Instead of mechanically aligning and fabricating precisely-spaced antenna elements across a large two-dimensional array, the system uses waveguide evanescent fields to optically connect to antenna elements, substituting mechanical precision requirements with optical field interaction that is more tolerant of fabrication variations and enables larger scale implementations
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 the creation of high-resolution, arbitrary far-field radiation patterns, expanding the capabilities of optical phased arrays beyond conventional beam focusing and steering, and enabling applications in communication, LADAR, holography, and sensing, while being tolerant to phase errors and cost-effective due to CMOS integration.
Implementation Method 1
at least one waveguide that is evanescently coupled to a plurality of antenna elements disposed in the same plane as the waveguide
Implementation Method 2
each antenna element may include a grating that diffracts at least part of the corresponding portion of the coherent optical beam so as to form the far-field radiation pattern
Implementation Method 3
the heater heats at least a portion of the variable optical delay line so as to change the shift in phase imparted on the corresponding portion of the coherent optical beam by the variable optical delay line
Data Source
AI summary
An optical phased array formed of a large number of nanophotonic antenna elements can be used to project complex images into the far field. These nanophotonic phased arrays, including the nanophotonic antenna elements and waveguides, can be formed on a single chip of silicon using complementary metal-oxide-semiconductor (CMOS) processes. Directional couplers evanescently couple light from the waveguides to the nanophotonic antenna elements, which emit the light as beams with phases and amplitudes selected so that the emitted beams interfere in the far field to produce the desired pattern. In some cases, each antenna in the phased array may be optically coupled to a corresponding variable delay line, such as a thermo-optically tuned waveguide or a liquid-filled cell, which can be used to vary the phase of the antenna's output (and the resulting far-field interference pattern).