Stepped Optical Coupler for Planar Waveguides
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Solution Overview
Problem
Existing optical couplers with smoothly tapered structures are difficult and expensive to manufacture, and they limit the acceptance angle, making them inefficient for coupling free space light beams into waveguides.
Innovation Solution
A planar waveguide with a stepped optical coupler structure, featuring stepwise decreases in thickness and corresponding increases in optical cladding, which reduces evanescent coupling and increases the acceptance angle, allowing for efficient coupling of light beams with a Gaussian profile, achieving coupling efficiency of at least 80%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a smoothly tapered optical coupler is used to couple light into a waveguide, then coupling efficiency can be achieved, but manufacturing difficulty and cost increase
Solution Approach 1:
The optical coupler is divided into multiple discrete thickness regions (first, second, third, fourth regions) with stepwise thickness variations. This segmentation replaces the continuous smooth taper with discrete steps, making the structure manufacturable using standard photolithography and deposition techniques while maintaining effective light coupling through controlled evanescent field interaction in each region.
2Reliability
If a smoothly tapered optical coupler is used, then light coupling can be achieved, but manufacturing cost increases
Solution Approach 1:
The coupler structure uses discrete thickness regions that can be manufactured using standard stepwise deposition or etching processes, avoiding the need for complex continuous taper fabrication. This segmentation enables cost-effective manufacturing while preserving the essential coupling function through controlled evanescent field interaction across the stepped interfaces.
3Reliability
If a smoothly tapered optical coupler is used, then coupling can occur, but acceptance angle is limited
Solution Approach 1:
Different regions of the optical coupler are assigned different thickness qualities (first region thinnest, fourth region thickest) to create localized evanescent field interaction zones. This local quality variation across the stepped structure enables broader angular acceptance by providing multiple coupling pathways for different incident angles, while each region maintains its specific function for efficient light transfer.
Data Source
AI summary
An optical coupler can be provided for coupling a light beam into a waveguide. The optical coupler can include a stepped structure, such as to reduce difficulties during manufacture, reduce expenses associated with manufacture, and additionally, to provide an increased acceptance angle of the optical coupler. The waveguide can include a guiding region where a cladding thickness can be increased relative to a coupling region, such as to reduce losses due to evanescent outcoupling in the guiding region.