Segmented Waveguide Optical Couplers for Compact Footprint
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Solution Overview
Problem
Conventional adiabatic 3-dB optical couplers have a large footprint, are wavelength dependent, sensitive to fabrication errors, and exhibit high insertion loss, limiting their effectiveness in photonics chips.
Innovation Solution
A structure for an optical coupler featuring a coupling section with laterally spaced waveguide cores, composed of materials with a refractive index between 2.5 and 5, patterned using lithography and etching processes, which includes tapered segments to facilitate efficient light coupling with reduced sensitivity to fabrication variations and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional adiabatic 3-dB optical couplers are used, then light coupling function is achieved, but footprint area is large
Solution Approach 1:
The waveguide structure is divided into multiple segments along the propagation direction, with each segment having different lateral spacing between waveguides. This segmentation allows the coupling section to be compact while maintaining effective light coupling through progressive mode coupling between segments.
Solution Approach 2:
Different sections of the waveguide structure have different local properties: the coupling section has gradually varying lateral spacing to enable adiabatic coupling, while other sections have fixed spacing for signal transmission. This local differentiation optimizes both coupling efficiency and overall device compactness.
2Adaptability or versatility
If conventional adiabatic 3-dB optical couplers are used, then light coupling function is achieved, but wavelength dependence increases
Solution Approach 1:
The lateral spacing between waveguides is gradually changed along the propagation direction in a controlled manner. This parameter variation enables the coupling section to operate effectively across a broader wavelength range by accommodating different phase velocities and coupling conditions for different wavelengths.
3Manufacturing precision
If conventional adiabatic 3-dB optical couplers are used, then light coupling function is achieved, but sensitivity to fabrication errors increases
Solution Approach 1:
The coupling section is designed with gradual parameter variation and extended interaction length, which provides tolerance against fabrication variations. The progressive coupling mechanism inherently compensates for small dimensional deviations, cushioning the system against fabrication errors before they can significantly impact performance.
4Loss of energy
If conventional adiabatic 3-dB optical couplers are used, then light coupling function is achieved, but insertion loss increases
Solution Approach 1:
The coupling process is divided into multiple segments with progressively changing spacing, allowing light to couple gradually from one waveguide to another. This segmented approach reduces abrupt mode transitions and minimizes radiation losses, thereby reducing overall insertion loss while maintaining coupling efficiency.
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 provides a compact, wavelength-independent optical coupler with reduced sensitivity to fabrication errors, achieving efficient light coupling with a desired ratio, such as 50%-50%, while minimizing footprint and operational overhead.
Implementation Method 1
waveguide cores (12, 14) and a coupling section (16) that are positioned over a dielectric layer (18)
Implementation Method 2
The section of the second waveguide core (14) and the section of the first waveguide core (12) are laterally spaced by a given distance
Data Source
AI summary
Structures for an optical coupler and methods of fabricating a structure for an optical coupler. A coupling section has a plurality of segments arranged with a pitch, a first waveguide core has a section extending longitudinally over the first plurality of segments of the coupling section, and a second waveguide core has a section extending longitudinally over the coupling section. The section of the second waveguide core laterally spaced from the section of the first waveguide core by a given distance.