Inverse Taper Optical Interconnect for Waveguide Coupling
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Solution Overview
Problem
The fabrication of high-aspect-ratio taper structures in polymer waveguides for efficient optical coupling with ion-exchanged glass waveguides is challenging due to complexities in etch-mask pattern formation, etching selectivity, and etch mask removal.
Innovation Solution
A method is presented for establishing optical coupling between spatially separated planar waveguides using an optical interconnect with inverse tapered end portions, allowing for an adiabatic transition of optical signals between waveguides with different refractive indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tapered waveguide structures are fabricated in polymer waveguides to enable efficient optical coupling with ion-exchanged glass waveguides, then coupling efficiency is improved, but fabrication complexity increases due to challenges in etch-mask pattern formation, etching selectivity, and etch mask removal
Solution Approach 1:
The patent introduces an intermediary inverse taper structure with high refractive index material between the polymer waveguide and the ion-exchanged glass waveguide. This intermediate structure mediates the optical coupling between the two waveguides with different refractive indices, achieving efficient coupling while avoiding the complex fabrication processes required for direct taper fabrication in polymer waveguides.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a high refractive index material in the inverse taper structure. This parameter change enables effective optical coupling between waveguides with different refractive indices (polymer and ion-exchanged glass) while simplifying the fabrication process compared to direct polymer taper fabrication.
2Reliability
If direct taper fabrication in polymer waveguides is attempted with 100 nm tip-width, then optical coupling with ion-exchanged glass waveguides is achieved, but manufacturing precision requirements become extremely high and fabrication yield decreases
Solution Approach 1:
The inverse taper structure with high refractive index material serves as an intermediary that relaxes the manufacturing precision requirements. Instead of requiring precise 100 nm tip-width tapers in polymer waveguides, the inverse taper structure provides a more robust coupling mechanism that is less sensitive to dimensional variations.
Solution Approach 2:
The patent inverts the conventional taper approach by using an inverse taper structure where the width increases rather than decreases toward the coupling interface. This inversion, combined with the high refractive index material, creates a coupling structure that is more tolerant to manufacturing variations while maintaining high coupling efficiency.
3Ease of manufacture
If conventional optical lithography is used to pattern waveguides, then fabrication is simpler, but feature sizes larger than 500 nm are achieved which is insufficient for 100 nm tip-width tapers
Solution Approach 1:
The inverse taper structure with high refractive index material acts as an intermediary that bridges the gap between conventional lithography capabilities and the required coupling precision. This structure can be fabricated with larger features using simpler lithography while still achieving the necessary optical coupling performance.
Solution Approach 2:
The patent changes the refractive index parameter of the coupling structure to compensate for larger feature sizes. By using high refractive index material in the inverse taper, the optical coupling efficiency is maintained even when the physical dimensions are larger than what would be required for direct polymer-to-glass coupling.
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 enables efficient optical coupling between polymer and ion-exchanged glass waveguides, achieving coupling efficiencies of 73% and 74% for TE and TM modes, respectively, while simplifying the fabrication process.
Implementation Method 1
enable an adiabatic transition of an optical signal from the first planar waveguide to the second planar waveguide via the optical interconnect
Implementation Method 2
efficient optical coupling between polymer and ion-exchanged glass waveguides
Data Source
AI summary
A method for establishing optical coupling between spatially separated first and second planar waveguides includes arranging an optical interconnect on the first planar waveguide. The optical interconnect has first and second end portions and an intermediate portion. Each of the end portions has an inverse taper. The second planar waveguide is arranged on the optical interconnect so that the second planar waveguide overlaps with one of the inverse tapered end portions but not the other inverse tapered end portion to thereby enable an adiabatic transition of an optical signal from the first planar waveguide to the second planar waveguide via the optical interconnect. The first and second planar waveguides have different refractive indices at an operating wavelength and the optical interconnect have a higher refractive index at the operating wavelength than the refractive indices of a core of the first planar waveguide and a core of the second planar waveguide.