VCSEL Arrays with Holographic Diffusers for Free Space Optical Comms
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Solution Overview
Problem
Current high power semiconductor laser transmitters for free space optical communications are cost-prohibitive for short distances and lack the necessary bandwidth and power to achieve precise alignment, leading to complex and expensive mechanical solutions.
Innovation Solution
The use of high power VCSEL arrays with holographic optical diffusing elements to create a semi-collimated beam bundle that reduces alignment tolerances and increases bandwidth, allowing for cost-effective high-speed optical wireless communications without mechanical means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high power semiconductor laser transmitters are used for free space optical communications, then bandwidth and transmission range are improved, but cost and system complexity become prohibitive
Solution Approach 1:
The patent segments a single high-power laser source into multiple lower-power VCSEL elements arranged in arrays. Each VCSEL element operates independently or in combination, allowing the system to achieve high total power output while using simpler, lower-cost individual components. This segmentation resolves the contradiction by distributing the bandwidth and power requirements across multiple elements rather than relying on a single complex high-power laser.
2Ease of manufacture
If single VCSEL devices are used, then bandwidth and cost are improved, but power output and alignment capability deteriorate
Solution Approach 1:
The patent merges multiple VCSEL devices into arrays where their optical outputs are combined through holographic optical elements. This merging allows the system to achieve high total power output comparable to single high-power lasers while maintaining the cost-effectiveness and ease of manufacture of individual VCSEL devices. The combined array output provides sufficient power for free space optical communication without requiring expensive single high-power laser sources.
3Reliability
If precise alignment is required for optical transmission, then transmission reliability is improved, but mechanical complexity and manufacturing cost increase
Solution Approach 1:
The patent employs holographic optical diffusing elements that dynamically adapt the optical beam characteristics. These elements create semi-collimated beam bundles that inherently provide larger spot sizes at the receiver, thereby relaxing alignment tolerances. The dynamic optical processing replaces rigid mechanical alignment requirements with flexible optical field manipulation, reducing mechanical complexity while maintaining transmission reliability.
4Manufacturing precision
If mechanical assembly components are used for fiber alignment, then alignment precision is improved, but device size and manufacturing cost increase
Solution Approach 1:
The patent replaces mechanical alignment components with holographic optical elements that perform alignment function through optical field manipulation. The VCSEL arrays combined with holographic diffusing elements create optical beams with inherent robustness to misalignment, eliminating the need for complex mechanical positioning mechanisms. This substitution reduces device size while maintaining manufacturing precision through optical rather than mechanical means.
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 solution enables unprecedented bandwidth levels at a reasonable cost, reduces cabling complexity, and enhances reliability by providing sufficient power density for signal-to-noise ratios, even with loose alignment tolerances, thus overcoming previous limitations in free space optical communications.
Implementation Method 1
VCSEL arrays with holographic optical diffusing elements to create a semi-collimated beam bundle
Data Source
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AI summary
High power, high speed VCSEL arrays are employed in unique configurations of arrays and sub-arrays. Placement of a VCSEL array behind a lens allows spatial separation and directivity. Diffusion may be employed to increase alignment tolerance. Intensity modulation may be performed by operating groups of VCSEL emitters at maximum bias. Optical communications networks with high bandwidth may employ angular, spatial, and/or wavelength multiplexing. A variety of network topologies and bandwidths suitable for the data center may be implemented. Eye safe networks may employ VCSEL emitters may be paired with optical elements to reduce optical power density to eye safe levels.