Sub-Pixel Photodetector Lens Array for High-Bandwidth Light Collection
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Solution Overview
Problem
High-data-rate optical communication systems require high-speed photodetectors with smaller optical apertures, which lead to reduced light detection efficiency due to smaller active areas, and existing solutions like giant micro-lenses are costly and difficult to fabricate.
Innovation Solution
A photodetecting device with a binned photodiode array comprising multiple sub-pixels and a micro-lens array, where each sub-pixel is covered by a smaller, easier-to-fabricate micro-lens, improving light coupling efficiency and reducing fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the optical aperture of the photodetector is reduced to increase bandwidth, then the speed of the photodetector is improved, but the light detection efficiency is reduced
Solution Approach 1:
The photodetector is divided into multiple sub-pixels (e.g., 2x2 array), each with its own micro-lens. This segmentation allows each sub-pixel to have a small active area for high bandwidth while the collective array maintains high light collection efficiency through multiple focused entry points.
Solution Approach 2:
Micro-lenses are introduced as intermediary optical elements that focus incoming light onto the small active areas of the sub-pixels. These micro-lens arrays act as mediators between the larger optical aperture and the small photodetector active areas, improving coupling efficiency without increasing the photodetector capacitance.
2Reliability
If a giant micro-lens is used to improve light coupling efficiency, then the light collection efficiency is enhanced, but the fabrication cost and difficulty increase
Solution Approach 1:
Instead of fabricating a single giant micro-lens, the system uses multiple small micro-lenses arranged in an array. Each micro-lens is much smaller and easier to fabricate with standard semiconductor processing techniques, while collectively providing the same or better optical coupling performance.
Solution Approach 2:
The solution transitions from a single large optical element in one dimension to multiple small elements arranged in a two-dimensional array, enabling easier fabrication while maintaining or improving overall performance through parallel light collection paths.
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 solution enhances light collection efficiency and reduces coupling loss while being more cost-effective and easier to manufacture compared to traditional giant micro-lens systems, maintaining high bandwidth and detection efficiency.
Implementation Method 1
the photosensitive layer being configured to absorb photons and generate photo-carriers
Implementation Method 2
a micro-lens array, where each sub-pixel is covered by a smaller, easier-to-fabricate micro-lens, improving light coupling efficiency
Data Source
AI summary
A photodetecting device includes a substrate, an array of sub-pixels, and a lens array covering the array of sub-pixels. Each sub-pixel includes a photosensitive layer supported by the substrate, the photosensitive layer being configured to absorb photons and generate photo-carriers, a first doped portion formed in the photosensitive layer of the respective sub-pixel, wherein the first doped portion includes dopants with a first conductivity type; and a second doped portion formed in the substrate, wherein the second doped portion includes dopants with a second conductivity type different from the first conductivity type. The array further includes an isolation region separating two or more sub-pixels of the array, a routing layer formed on the substrate configured to electrically couple a circuit to multiple sub-pixels of the array. The lens array includes a spacer portion and a plurality of lenses arranged in a one-to-one correspondence with each of the sub-pixels.