Diagonal Offset Optical Couplers for Low-Loss Light Transfer
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Solution Overview
Problem
Conventional optical couplers and splitters in photonics chips have a large footprint, are wavelength dependent, sensitive to fabrication errors, and exhibit high loss, especially for transverse magnetic polarization mode due to abrupt mode conversion.
Innovation Solution
A structure for an optical coupler featuring two tapered waveguide cores with lateral and vertical offsets, allowing for adiabatic evanescent coupling with minimal loss, where the second tapered section is positioned diagonally relative to the first, enabling efficient transfer of light between waveguide cores with different materials and orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional optical couplers are used, then light transfer between waveguide cores is achieved, but the device exhibits high insertion loss especially for transverse magnetic polarization mode due to abrupt mode conversion
Solution Approach 1:
The patent introduces a diagonal offset configuration between the first and second waveguide cores, positioning them at different lateral and vertical positions. This spatial arrangement in multiple dimensions enables adiabatic mode conversion, allowing light to transfer gradually from one waveguide core to another without abrupt mode changes, thereby reducing insertion loss for both TE and TM polarization modes
Solution Approach 2:
The patent employs tapered sections at the ends of both waveguide cores, where the width of the waveguides gradually changes. This continuous parameter change enables adiabatic coupling by slowly transforming the mode profile as light propagates through the tapered region, preventing abrupt mode conversion and minimizing insertion loss for all polarization modes
2Loss of energy
If conventional optical couplers are used, then light transfer is achieved, but the device has a large footprint
Solution Approach 1:
By utilizing diagonal offset positioning with both lateral and vertical separation between waveguide cores, the patent achieves efficient light transfer over a compact area. The three-dimensional spatial arrangement allows the coupling region to be more compact compared to conventional lateral-only offset couplers, reducing the overall footprint while maintaining low insertion loss
Solution Approach 2:
The patent employs asymmetric tapered sections with different width variations at the ends of the waveguide cores. The first waveguide core has a taper with specific width changes, while the second waveguide core has a complementary asymmetric taper. This asymmetric design optimizes the coupling efficiency within a reduced footprint area
3Reliability
If conventional optical couplers are used, then coupling between waveguide cores is achieved, but the device is sensitive to fabrication errors
Solution Approach 1:
The patent designs the waveguide cores with tapered sections that provide a gradual transition region. This tapered geometry acts as a cushioning mechanism that compensates for fabrication tolerances and alignment errors. The gradual width change in the tapers makes the coupling less sensitive to small variations in waveguide dimensions and positioning, thereby improving fabrication tolerance
Solution Approach 2:
The patent employs waveguide cores with different material compositions - the first waveguide core has a first material and the second waveguide core has a second material. This composite material approach allows optimization of each waveguide for its specific function while the tapered interfaces between different materials provide robust coupling that is tolerant to fabrication variations
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
The solution results in a compact optical coupler with low insertion loss for both transverse electric and magnetic polarization modes, reducing the footprint and sensitivity to fabrication errors while maintaining efficient light transfer.
Implementation Method 1
allowing for adiabatic evanescent coupling with minimal loss
Implementation Method 2
allowing for adiabatic evanescent coupling with minimal loss
Data Source
AI summary
Structures for an optical coupler and methods of fabricating a structure for an optical coupler. The structure includes a first waveguide core having a first tapered section and a second waveguide core having a second tapered section positioned adjacent to the first tapered section of the first waveguide core. The second tapered section is positioned with a lateral offset in a lateral direction relative to the first tapered section. The second tapered section is positioned with a vertical offset in a vertical direction relative to the first tapered section.