Curved Optical Coupler for Vertical-to-Horizontal Light Routing
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Solution Overview
Problem
Efficiently coupling an optical fiber to an optical waveguide in semiconductor structures is challenging due to significant optical loss caused by the large diameter difference between the fiber and waveguide, requiring precise and costly alignment packaging schemes.
Innovation Solution
A curved optical coupler is formed with one end contacting the semiconductor substrate and the other end contacting the optical waveguide, changing the light direction from vertical to horizontal, facilitated by a silicon structure with a cladding layer and optionally a lens or antireflective coating to minimize optical loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a straight optical coupler is used to couple light from the backside substrate to the frontside waveguide, then the structural complexity is low, but the optical loss is high due to large angle change and diameter mismatch
Solution Approach 1:
The optical coupler employs a curved geometry instead of a straight configuration. The curve radius is specifically designed to be at least 5 times the width of the optical waveguide, allowing light to gradually change direction from vertical (backside) to horizontal (frontside) with minimal reflection and scattering losses, thereby reducing overall optical loss while maintaining manufacturability
Solution Approach 2:
The coupler transitions light propagation from the vertical dimension (z-axis, backside to frontside) to the horizontal dimension (x-axis, waveguide direction) through a controlled curved path within the substrate thickness, efficiently utilizing the third dimension to resolve the direction change requirement
2Measurement precision
If precise submicron alignment packaging schemes are used to align the integrated circuit to an optical fiber, then the coupling precision is high, but the manufacturing cost is very costly
Solution Approach 1:
The optical coupler is pre-formed within the substrate during the semiconductor fabrication process itself, establishing the optical coupling path before final assembly. This preliminary formation of the coupling structure eliminates the need for post-fabrication alignment adjustments and reduces packaging complexity
Solution Approach 2:
The curved coupler structure inherently guides light from the backside input to the frontside waveguide output through its geometric design, making the alignment self-evident and reducing dependency on complex external alignment mechanisms. The structure serves its own alignment function
3Use of energy by moving object
If the diameter of the optical fiber is substantially larger than the diameter of the waveguide, then the fiber can transmit more light, but substantial optical loss occurs when coupling the fiber to the waveguide
Solution Approach 1:
The optical coupler structure is designed with varying local properties: the input region at the backside has a larger effective area to match the fiber diameter, while the output region at the frontside tapers to match the smaller waveguide diameter. This gradual transition in local dimensions minimizes reflection and mode mismatch losses
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 effectively reduces optical loss by aligning and focusing light from the fiber to the waveguide, minimizing the angle change and achieving efficient coupling without the need for precise submicron alignment, thus enhancing the integration of optical and electrical signals in photonic devices.
Implementation Method 1
The optical coupler is configured to change a direction of travel of light from a first direction at the first end to a second direction at the second end
Implementation Method 2
The optical coupler is curved between the first end and the second end, facilitating efficient light coupling through directional change
Data Source
AI summary
A method of manufacturing a device includes forming an optical coupler having a first end contacting a front side of a semiconductor substrate and a second end contacting an optical waveguide on an insulator layer on the substrate. The optical coupler is curved between the first end and the second end. The optical coupler is configured to change a direction of travel of light from a first direction at the first end to a second direction at the second end.