Normal Incidence Photodetector Self-Test via Waveguide Coupling
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Solution Overview
Problem
Photonic integrated circuits (PICs) face a trade-off between low insertion losses for normal operation and self-test functionality, as normal incidence photodetectors (NIPDs) are not suited for self-testing due to difficulties in optical coupling with on-chip waveguides, while waveguide-based photodetectors suffer from higher insertion losses during normal operation.
Innovation Solution
NIPD structures are designed to enable both normal-incidence and in-plane detection, integrating III-V materials with silicon photonics, allowing for self-tests while maintaining low insertion losses, using flared-out or wrap-around waveguide structures to couple light into the NIPD for self-testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If waveguide-based photodetectors are used for self-testing, then self-test functionality is achieved, but insertion losses increase during normal operation
Solution Approach 1:
The NIPD structure is designed to perform multiple functions: it detects light in normal operation mode and also enables self-test functionality through integrated waveguide coupling structures. The photodetector can be optically coupled to both external fiber sources and on-chip waveguides, allowing it to serve as both a receiver and a testable component.
Solution Approach 2:
Waveguide structures act as intermediaries to couple light from on-chip sources to the NIPD for self-testing purposes. These waveguide structures enable optical coupling between components that would otherwise be difficult to connect, facilitating self-test functionality without requiring external test equipment.
2Loss of energy
If normal incidence photodetectors are used for normal operation, then insertion losses are minimized, but self-test functionality cannot be achieved
Solution Approach 1:
The invention merges the NIPD structure with waveguide coupling capabilities by integrating waveguide structures directly with the photodetector. This combination allows the NIPD to maintain its low insertion loss characteristics while gaining the ability to be tested through on-chip waveguide routing.
Solution Approach 2:
The waveguide structures extend in the plane of the chip, providing an additional dimensional pathway for light coupling. This planar waveguide approach complements the vertical light incidence of the NIPD, enabling self-test functionality through in-plane light routing while maintaining normal vertical detection operation.
3Adaptability or versatility
If waveguide coupling structures are added to NIPD, then self-test functionality is enabled, but device complexity increases
Solution Approach 1:
The waveguide coupling structure is segmented into distinct functional regions: flared waveguide sections for mode matching, wrap-around portions for edge coupling, and integration zones with the NIPD. This segmentation allows each portion to be optimized independently while maintaining overall functionality.
Solution Approach 2:
The waveguide structures employ curved and flared geometries to gradually transition optical modes and improve coupling efficiency. The flared-out and wrap-around configurations use curved paths to guide light around the NIPD structure, enabling optical access without straight-line constraints.
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
Enables self-testing of NIPDs with standard manufacturing equipment, reducing test time and cost, and maintaining high normal-operation performance by minimizing optical losses and ensuring high-volume manufacturing feasibility.
Implementation Method 1
a waveguide formed in a semiconductor device layer of the SOI substrate and configured to couple light into the p-i-n mesa
Implementation Method 2
a p-i-n mesa disposed on a semiconductor-on-insulator (SOI) substrate, the p-i-n mesa comprising n-type, active, and p-type semiconductor layers
Data Source
AI summary
Photonically integrated normal incidence photodetectors (NIPDs) and associated in-plane waveguide structures optically coupled to the NIPDs can be configured to allow for both in-plane and normal-incidence detection. In photonic circuits with light-generation capabilities, such as integrated optical transceivers, the ability of the NIPDs to detect in-plane light is used, in accordance with some embodiments, to provide self-test functionality.