Inverted H-tree Unit Cell for Optical Phased Array Bandwidth
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Solution Overview
Problem
Next-generation optical phased arrays for free-space optical systems face limitations in achieving high fill factor and data rates due to differences in path lengths among nano-antennas, which restricts the useable optical bandwidth and range in existing designs like the Manhattan and Euler H-tree arrangements.
Innovation Solution
A photonic integrated circuit with an inverted H-tree unit cell design, where antenna elements are arranged in an inverted H-tree configuration with equal path lengths and paired to common signal pathways, allowing for symmetric far-field emissions independent of rotation, thereby enhancing bandwidth and data rates while maintaining a high fill factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional Manhattan or H-tree arrangements are used, then the optical phased array can be implemented, but path length differences among nano-antennas limit the usable optical bandwidth and data rates
Solution Approach 1:
The patent inverts the traditional H-tree configuration to create an inverted H-tree unit cell design. This inversion repositions the beam splitter at the center and arranges nano-antennas at the endpoints of the inverted H-structure, creating symmetric path lengths from the beam splitter to all antenna elements. This geometric inversion resolves the path length disparity problem that limits bandwidth and data rates in conventional designs.
Solution Approach 2:
The patent employs asymmetric positioning of antenna subsets within the inverted H-tree structure, where a first subset of antenna elements is oriented in a first direction and a second subset is oriented in a second direction opposite the first direction. This asymmetric yet balanced configuration enables symmetric far-field emissions while maintaining equal path lengths, thereby improving bandwidth without sacrificing directional control.
2Device complexity
If path length differences are present among nano-antennas, then the optical phased array structure is simpler to implement, but the usable optical bandwidth and range are restricted
Solution Approach 1:
By inverting the H-tree configuration, the patent achieves symmetric path lengths to all antenna elements while maintaining a relatively simple signal pathway structure. The inverted H-tree geometry naturally provides equal path lengths from the central beam splitter to all antenna endpoints, eliminating the need for complex compensatory structures and thereby preserving simplicity while expanding optical bandwidth.
3Productivity
If antenna elements are arranged in inverted H-tree configuration with equal path lengths, then optical bandwidth and data rates increase, but the structural design becomes more complex
Solution Approach 1:
The optical phased array is divided into multiple identical inverted H-tree unit cells, each containing a standardized set of antenna elements and signal pathways. This segmentation into modular unit cells simplifies the overall design process, as each unit can be independently designed and fabricated, then replicated to build larger arrays with consistent performance characteristics.
Solution Approach 2:
Multiple antenna elements are optically coupled to common signal pathways within each inverted H-tree unit cell. This merging of antenna elements with shared beam splitters and waveguides reduces the total number of independent signal pathways required, thereby decreasing structural complexity while maintaining equal path lengths and high data rates.
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
The inverted H-tree unit cell design achieves increased optical bandwidth and data rates with improved range and field of regard, comparable to Manhattan-style designs, while ensuring symmetric emissions and reduced path length disparities.
Implementation Method 1
multiple phase modulators configured to modify phases of the optical signals being transported through the signal pathways
Data Source
AI summary
An apparatus includes a photonic integrated circuit having an optical phased array, where the optical phased array includes multiple unit cells. Each unit cell includes multiple antenna elements configured to transmit or receive optical signals, where a first subset of the antenna elements is oriented in a first direction and a second subset of the antenna elements is oriented in a second direction opposite the first direction. Each unit cell also includes multiple signal pathways configured to transport the optical signals to or from the antenna elements, where at least some of the signal pathways have an “H” configuration. Each unit cell further includes multiple phase modulators configured to modify phases of the optical signals being transported through the signal pathways.