Optical Phased Array Lens Imaging for Side Lobe Reduction
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Solution Overview
Problem
Optical phased arrays face limitations in steering range and beam-width due to large spacing between emitting elements, resulting in undesired side lobes in the far-field pattern.
Innovation Solution
Incorporating optical signal emitting elements with associated lenses, such as grating or edge couplers, and positioning them with concave or convex lenses to form images, effectively increasing the effective width of emitting elements or reducing the distance between them, thereby enhancing the steering angle and improving the far-field radiation pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If emitting elements are placed multiple wavelength apart to compensate for small wavelength and routing challenges, then routing challenges are reduced, but undesired side lobes appear in the far-field pattern and steering range is limited
Solution Approach 1:
Lens elements are introduced as intermediary components between the emitting elements and free space. These lenses optically image the emitting elements, creating virtual sources that are closer together than the physical emitting elements. This intermediary imaging process allows the physical elements to be spaced apart for manufacturability while the optical images maintain closer effective spacing to reduce side lobes.
Solution Approach 2:
The lens system creates optical copies (images) of the emitting elements. These copied images serve as the effective radiation sources in the far-field pattern, replacing the need for closely-spaced physical elements. The copies have the same optical properties as the originals but can be positioned differently through the imaging process, enabling reduced side lobe levels while maintaining manufacturable element spacing.
2Ease of manufacture
If emitting elements are spaced further apart, then routing challenges are reduced, but beam-width effect becomes undesirable and steering range is limited
Solution Approach 1:
The lens acts as an intermediary that decouples the physical spacing of emitting elements from the effective spacing of radiation sources. By imaging the elements through the lens, the system achieves effective closer spacing (improving steering range) while allowing physical elements to be spaced further apart (improving routing and manufacturability).
Solution Approach 2:
The lens changes the effective parameters of the emitting elements by creating magnified or demagnified images. This parameter transformation allows the system to achieve different effective element spacings and beam widths without changing the physical element positions, thereby improving steering range while maintaining manufacturable spacing.
3Object-affected harmful factors
If emitting elements are placed closer together, then side lobes are reduced, but routing challenges increase
Solution Approach 1:
The lens system serves as an intermediary that allows physical elements to be spaced apart (easy routing) while creating optical images that are effectively closer together (reduced side lobes). The lens transforms the spatial relationship between elements and their radiation patterns, enabling both benefits simultaneously.
Solution Approach 2:
By creating optical copies of the emitting elements through imaging, the system achieves the side lobe reduction benefits of closely-spaced elements without the manufacturing difficulties. The copies can be positioned optimally for performance while the originals maintain manufacturable spacing for routing and assembly.
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 results in a wider beam-width and increased steering angle, reducing side lobes and improving the overall far-field radiation pattern of optical phased arrays.
Implementation Method 1
N lenses each associated with a different one of the N optical signal emitting elements and positioned to form an image of its associated signal emitting element
Implementation Method 2
the optical phased array further includes, in part, a concave lens positioned between the N signal emitting elements and the N lenses. In one embodiment, the optical phased array further includes, in part, a convex lens positioned between the N signal emitting elements and the N lenses
Data Source
AI summary
An optical phased array includes, in part, N optical signal emitting elements, and N lenses each associated with a different one of the N optical signal emitting elements and positioned to form an image of its associated signal emitting element, where N is an integer greater than 1. The optical signal emitting elements may be a grating coupler, an edge coupler, and the like. At least a number of the lenses may be formed from Silicon. The optical phased array may optionally include one or more concave or convex lens positioned between the signal emitting elements and the N lenses. The optical signal emitting elements may be formed in a silicon dioxide layer formed above a semiconductor substrate and the lenses may be formed from Silicon disposed above the silicon dioxide layer. The optical signal emitting elements may receive an optical signal generated by the same source.