Integrated Photonic Platform for Low-Loss Nonlinear Frequency Conversion
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Solution Overview
Problem
The challenge in developing photonic integrated circuits (PICs) using silicon or indium phosphide materials lies in the difficulty of achieving efficient optical coupling between dissimilar materials with significant refractive index differences, leading to complex and costly packaging, limited wavelength range, and high optical losses, particularly when using indirect bandgap materials like silicon, which requires precise alignment and small taper tip dimensions.
Innovation Solution
The implementation of a butt-coupling scheme combined with a mode-converter and non-linear elements for frequency conversion, allowing for efficient optical coupling between dissimilar materials by using an intermediate waveguide with optimized refractive index and thickness, reducing the need for narrow taper tips and enabling scalable manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If taper structures are used to transfer optical signals between dissimilar materials, then power transfer efficiency is improved, but the requirements on taper tip dimensions become extremely small (tens of nanometers) which increases device complexity and manufacturing difficulty
Solution Approach 1:
The patent introduces an intermediate waveguide layer with refractive index between the high-index semiconductor material and low-index dielectric material. This intermediate layer acts as a mediator that gradually transitions the optical mode between dissimilar materials, eliminating the need for extremely small taper tips while maintaining efficient power transfer. The intermediate layer profile is specifically designed to enable adiabatic mode transformation across the refractive index boundary.
Solution Approach 2:
The patent changes the refractive index parameter by introducing an intermediate material layer with refractive index介于 between the semiconductor and dielectric materials. This parameter transition allows the optical mode to adapt gradually from the high-index semiconductor waveguide to the low-index dielectric waveguide, avoiding the need for sub-100nm taper dimensions while maintaining low loss coupling.
2Loss of energy
If precise alignment is used to assemble PICs from separately processed chips, then optical coupling efficiency is improved, but packaging complexity and cost increase significantly
Solution Approach 1:
The patent merges the optical coupling function into the wafer bonding process itself by integrating the intermediate waveguide layer into the bonded structure. This eliminates the need for separate post-bonding alignment and adjustment steps, as the coupling is achieved through the designed refractive index profile rather than mechanical alignment precision.
Solution Approach 2:
The intermediate waveguide layer serves as a mediator that provides inherent mode matching between dissimilar materials, replacing the need for precise mechanical alignment. The refractive index transition layer ensures efficient optical coupling through its designed profile, making the system insensitive to alignment variations.
3Power
If low refractive index dielectric materials are used for waveguides, then high power handling capability is improved, but coupling efficiency with high index semiconductor materials deteriorates
Solution Approach 1:
The patent introduces an intermediate waveguide layer with refractive index between the high-index semiconductor material and low-index dielectric material. This intermediate layer acts as a mediator that gradually transitions the optical mode between dissimilar materials, eliminating the need for extremely small taper tips while maintaining efficient power transfer. The intermediate layer profile is specifically designed to enable adiabatic mode transformation across the refractive index boundary.
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 facilitates efficient frequency conversion and scalable manufacturing of high-performance PICs that can operate across challenging wavelength ranges, handling high optical powers and reducing fabrication complexity, while allowing for precise optical alignment through lithographic techniques.
Implementation Method 1
a non-linear element used to convert the frequency of the direct injection optical source. Multiple non-linear effects can be utilized, and in some embodiments second harmonic generation enables chip-scale optical source performance at certain optical wavelengths
Implementation Method 2
To transfer the optical signal between dissimilar materials, the heterogeneous approach utilizes tapers whose dimensions are gradually reduced until the effective mode refractive indices of dissimilar materials match and there is efficient power transfer
Data Source
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AI summary
A device comprises first, second and third elements fabricated on a common substrate. The first element comprises an active waveguide structure comprising: a first portion supporting a first optical mode. The second element comprises a passive waveguide structure supporting a second optical mode. The third element, at least partly butt-coupled to the second portion, comprises an intermediate waveguide structure supporting intermediate optical modes. At least part of the second element is non-linear, supporting frequency conversion. A tapered waveguide structure in at least one of the second and third elements facilitates efficient adiabatic transformation between the first optical mode and one intermediate optical mode. No adiabatic transformation occurs between any intermediate optical mode and the first optical mode. Mutual alignments of the elements are defined using lithographic alignment marks.