Removable Optical Tap for Silicon Photonics In-Process Trimming
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Solution Overview
Problem
Silicon photonics face challenges in accurately measuring and correcting optical characteristics during fabrication due to sensitivity to fabrication variations, which is difficult without modifying the device and impacting its performance, and existing methods like vertical grating couplers are costly and invasive.
Innovation Solution
A photonic chip with a removable optical tap and decoupling material, allowing for precise measurement and trimming of optical waveguides without thermal or electronic tuning, using oxidation to adjust the refractive index and achieve target wavelengths with high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a vertical grating coupler is added to enable optical measurement during fabrication, then measurement capability is improved, but device complexity and manufacturing cost increase due to additional fabrication operations and materials
Solution Approach 1:
The patent extracts the optical measurement function from the main device structure by using a separate optical access path through the side wall of the waveguide, rather than integrating a complex vertical grating coupler into the device. This allows optical characterization without adding significant structural complexity to the device itself.
Solution Approach 2:
The patent introduces an intermediary optical access mechanism (side wall optical tap) that mediates between the optical waveguide and external measurement equipment. This intermediary structure enables optical measurement without requiring direct integration of complex coupling elements into the device architecture.
2Measurement precision
If a vertical grating coupler is added to enable optical measurement during fabrication, then measurement capability is improved, but manufacturing time and cost increase due to additional fabrication operations
Solution Approach 1:
The patent merges the optical measurement function with existing fabrication steps by forming the optical access structure during the standard waveguide fabrication process. The side wall optical tap is created as part of the waveguide formation sequence, eliminating the need for separate post-fabrication coupling operations.
Solution Approach 2:
The patent performs preliminary formation of the optical access structure during early fabrication stages rather than adding it later. The side wall optical tap is prepared in advance as part of the waveguide fabrication sequence, enabling optical measurement without requiring additional time-consuming operations after device completion.
3Measurement precision
If a vertical grating coupler is added to enable optical measurement during fabrication, then measurement capability is improved, but device performance may be adversely impacted due to invasive fabrication operations
Solution Approach 1:
The patent applies local quality modification by creating a localized optical access point at the side wall of the waveguide rather than modifying the entire device structure. This localized approach enables optical measurement without adversely affecting the overall device performance or requiring invasive fabrication operations throughout the device.
Solution Approach 2:
The patent segments the optical measurement function from the main device body by providing a separate side wall optical access path. This segmentation allows optical characterization without requiring the main device structure to be modified or compromised by invasive fabrication operations.
4Ease of manufacture
If the optical waveguide width is decreased to improve optical coupling, then coupling efficiency is improved, but fabrication precision requirements increase due to sensitivity to dimensional variations
Solution Approach 1:
The patent transitions from optimizing coupling by modifying waveguide width (one-dimensional adjustment) to achieving coupling through side wall optical access (two-dimensional approach). This dimensional change allows optical coupling without requiring extremely precise control of waveguide width, as the optical access is provided through the side wall rather than by narrowing the waveguide itself.
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 accurate and non-invasive characterization and trimming of optical waveguides, improving yield and reducing costs by allowing for in-process correction of fabrication variations without affecting the device's performance.
Implementation Method 1
an optical waveguide that conveys an optical signal having a carrier wavelength
Implementation Method 2
the optical waveguide may be trimmed by oxidizing the semiconductor layer proximate to the optical waveguide
Data Source
AI summary
An integrated circuit includes optical waveguides defined in a semiconductor layer, and uses removable optical taps to allow for in-process characterization and trimming. These optical waveguides may be trimmed during fabrication of the integrated circuit to improve performance. Note that the trimming may modify indexes of refraction of portions of the optical waveguides or may involve a more invasive process. Moreover, the trimming may exclude or may not involve the use of a polymer and/or the carrier wavelengths at a given temperature may be stable as a function of time. The trimming process may use removable optical taps for external feedback to determine the amount of change required. These optical taps may be formed either in the semiconductor layer or the cladding layer, and they may be disabled with negligible impact to device performance via alterations to the cladding layer after the completion of trimming.