Microring Cavity Waveguide Photodetector for High Responsivity Bandwidth
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Solution Overview
Problem
Existing photodetectors face challenges in achieving high responsivity for visible and near-infrared light without compromising device speed, particularly due to non-orthogonal orientations of light propagation and charge carrier transport axes, leading to limited optical-electrical bandwidth.
Innovation Solution
The integrated cavity-enhanced photodetector design features a low-loss waveguide with a bus layer and a microring resonator (MRR) layer, a photodetector layer positioned underneath the MRR, and a phase shifter coupled with the MRR. The light propagation axis in the MRR is orthogonal to the charge carrier transport axis in the photodetector layer, enhancing responsivity while maintaining high bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the photodetector length is increased to improve responsivity, then the optical absorption is enhanced, but the charge carrier transport time is prolonged, limiting the optical-electrical bandwidth
Solution Approach 1:
The patent introduces a vertical cavity structure where light propagates along the vertical axis (z-direction) through the photodetector layer, while charge carriers are collected horizontally at the edges (x-y plane). This dimensional separation allows the light propagation path to be independent of the charge carrier collection distance, resolving the trade-off between absorption length and carrier transport time
Solution Approach 2:
The patent embeds the photodetector layer within a microring resonator cavity structure, where the photodetector is nested inside the optical cavity. This nesting allows the optical field to be confined and enhanced within the cavity region, increasing the effective absorption path length without requiring a longer physical photodetector device, thereby maintaining high bandwidth
2Ease of manufacture
If a same-layer SiN and Si deposition is used for integration, then the fabrication is simplified, but the carrier transport axis becomes parallel to the light propagation direction, limiting bandwidth
Solution Approach 1:
The patent transitions from same-layer to multi-layer integration, stacking the SiN waveguide layer above the Si photodetector layer. This vertical stacking enables the light propagation axis (vertical) to be orthogonal to the charge carrier transport axis (horizontal), achieving high bandwidth while maintaining fabrication compatibility through standard multi-layer deposition processes
3Ease of operation
If evanescent coupling is used to transfer light between waveguides, then the coupling is achieved, but very long coupling lengths are required due to weak evanescent tail at visible wavelengths, creating a trade-off between responsivity and bandwidth
Solution Approach 1:
The patent employs microring resonators that utilize optical resonance to enhance light-matter interaction. The resonant circulating field within the microring cavity provides strong field confinement and enhanced evanescent coupling, enabling efficient light transfer and photodetection over short interaction lengths, thereby avoiding the need for long coupling lengths
Solution Approach 2:
The patent changes the operational parameters by using resonance enhancement to increase the optical field intensity within the photodetector region. This parameter change (resonant field enhancement) compensates for the weak evanescent tail at visible wavelengths, achieving efficient coupling and high responsivity without requiring long device lengths
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 design achieves high responsivity and optical-electrical bandwidth, independent of photodetector length, allowing for efficient visible and near-infrared light detection without compromising device speed.
Implementation Method 1
resonance cavity enhancement of the optical field at photoabsorption region
Implementation Method 2
efficient photodetection for visible light
Data Source
AI summary
An integrated cavity-enhanced photodetector for visible photonics is provided. The photodetector includes a waveguide, an absorption layer, a set of metal contacts and a phase shifter. The photodetector can be used for visible photonics with multi-material integration flow and low loss.