Curved Photodetector Structure for Back Reflection Suppression
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Solution Overview
Problem
Conventional photodetectors in photonics chips suffer from significant back reflection due to refractive index mismatch, leading to reduced responsivity and quantum efficiency, and have a large device footprint that degrades optical-to-electrical bandwidth.
Innovation Solution
A structure featuring a waveguide core with a light-absorbing layer having an annular portion and laterally spaced tapers adjacent to the waveguide core, which reduces back reflection and enhances optical coupling, comprising a semiconductor material with a light-absorbing material like germanium that generates charge carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional photodetector structure is used, then the device can detect optical signals, but significant back reflection occurs due to refractive index mismatch between the photodetector material and waveguide material
Solution Approach 1:
The patent applies the principle of converting the harmful back reflection into a beneficial effect by introducing a light-absorbing layer that absorbs the reflected light and converts it into electrical signals. This layer transforms the harmful reflected energy into useful photocurrent, thereby improving responsivity and quantum efficiency while reducing the negative impact of back reflection.
Solution Approach 2:
The patent introduces a light-absorbing layer as an intermediary between the waveguide and the photodetector. This intermediary layer serves as a mediator that captures the back-reflected light before it returns to the waveguide, converting optical energy into electrical energy and preventing the harmful reflection from degrading system performance.
2Reliability
If a conventional photodetector structure is used, then the device can function as a photodetector, but the device footprint is large which degrades the optical-to-electrical bandwidth
Solution Approach 1:
The patent segments the photodetector structure into distinct functional regions: a waveguide core for light transmission, a light-absorbing layer for optical-to-electrical conversion, and contact structures for electrical extraction. This segmentation allows each component to be optimized for its specific function while maintaining a compact overall footprint, thereby improving bandwidth without sacrificing functionality.
Solution Approach 2:
The patent transitions from a planar two-dimensional photodetector structure to a three-dimensional vertically stacked structure. By stacking the light-absorbing layer above the waveguide core and using vertical contacts, the design achieves high optical-to-electrical bandwidth in a reduced lateral footprint, effectively utilizing the vertical dimension to overcome the area-bandwidth tradeoff.
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 improves device efficiency and optical-to-electrical bandwidth by suppressing back reflection and reducing the device footprint, leading to enhanced performance of the photodetector with efficient optical coupling.
Implementation Method 1
a light-absorbing layer on the pad adjacent to the waveguide core. The light-absorbing layer includes an annular portion, a first taper, and a second taper laterally spaced from the first taper
Data Source
AI summary
Structures for a photodetector or terminator and methods of fabricating a structure for a photodetector or terminator. The structure includes a waveguide core having a longitudinal axis, a pad connected to the waveguide core, and a light-absorbing layer on the pad adjacent to the waveguide core. The light-absorbing layer includes an annular portion, a first taper, and a second taper laterally spaced from the first taper. The first taper and the second taper are positioned adjacent to the waveguide core.