Wafer-Scale Optical Chip Testing via Grating Couplers
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Solution Overview
Problem
Conventional optical chip testing methods require significant alignment efforts and are inefficient, especially when testing optical chips in a wafer state, as they necessitate precise alignment of optical axes and light input from the wafer surface, leading to increased workload and potential measurement inaccuracies.
Innovation Solution
The implementation of a testing system that includes a wafer with a plurality of optical chips, each equipped with a test circuit featuring grating couplers and branch couplers, which allows for automatic optical connection via an optical fiber array without the need for alignment, enabling efficient measurement of test light power by switching between different grating couplers and polarization modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual alignment of optical axes is performed for each optical chip, then measurement precision can be maintained, but work efficiency deteriorates due to increased alignment workload
Solution Approach 1:
The system enables self-alignment through the use of grating couplers that automatically couple light between optical fibers and waveguides without requiring manual alignment. The optical chip testing apparatus allows multiple chips to be tested simultaneously on a wafer substrate, with the test light automatically routed to each chip through the grating coupler structure, eliminating the need for operator intervention in alignment procedures.
Solution Approach 2:
The testing system is divided into independent testing channels, each with its own grating coupler and optical path. This segmentation allows multiple optical chips to be tested in parallel on a single wafer, with each chip receiving test light through dedicated optical fibers coupled to grating couplers, thereby multiplying productivity while maintaining individual measurement precision.
2Productivity
If optical chips are tested in wafer state with surface light input, then productivity improves through batch testing, but measurement precision deteriorates due to alignment difficulties
Solution Approach 1:
The patent replaces mechanical alignment systems with optical grating couplers that provide automatic coupling between optical fibers and waveguides. The grating couplers use diffraction grating structures to couple light at specific angles, eliminating the need for precise mechanical alignment of optical components while enabling batch testing of multiple chips on a wafer substrate.
Solution Approach 2:
Grating couplers serve as intermediary components between optical fibers and integrated circuit waveguides. These couplers facilitate automatic light coupling without requiring direct mechanical contact or precise alignment between the fiber and waveguide, thereby enabling high-productivity batch testing while maintaining measurement precision through consistent optical coupling.
3Ease of operation
If grating couplers are used for automatic optical connection, then ease of operation improves by eliminating alignment, but device complexity increases due to additional components
Solution Approach 1:
The grating coupler structure integrates multiple functions into a single component: it serves as both the optical coupling interface and the wavelength filtering element. By merging the coupling and filtering functions into the grating coupler, the system achieves ease of operation through automatic alignment while minimizing the increase in device complexity compared to using separate alignment mechanisms and filters.
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 approach improves work efficiency by eliminating the need for manual alignment and enhances measurement precision by using symmetrical branch couplers and polarization rotators to maintain consistent light loss across different wavelengths and polarization modes, facilitating high-precision testing of optical chips in a wafer state.
Implementation Method 1
a first grating coupler configured to receive test light
Implementation Method 2
switching between different grating couplers and polarization modes
Data Source
AI summary
An optical device includes an optical circuit and a test circuit optically connected to the optical circuit. The test circuit includes a first grating coupler configured to receive test light, a second grating coupler configured to output, as reference light, the test light passed through the first grating coupler, and a first branch coupler connected to an output of the first grating coupler. The first branch coupler includes first output connected to an input of the optical circuit and configured to branch and output the test light from the first grating coupler to the optical circuit. Further, the first branch coupler includes a second output connected to an input of the second grating coupler and configured to branch and output the test light from the first grating coupler to the second grating coupler.