Optical Waveguide Joint Regions for Low-Loss Photomask Alignment
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Solution Overview
Problem
Existing optical circuits face challenges in bending light with a small bending radius while maintaining low loss, and the alignment accuracy of multiple photomasks leads to significant losses at joint portions due to optical axis positional deviations.
Innovation Solution
The optical waveguide is manufactured using a photomask that divides the waveguide pattern into regions with joint regions where the waveguide width changes, allowing for overlapping and exposure of photomasks to connect waveguides, with taper patterns that gradually adjust the width to minimize optical axis positional deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple photomasks are used to divide and draw waveguide patterns, then large-scale optical circuits can be manufactured, but alignment accuracy deteriorates causing optical axis positional deviations at joint portions
Solution Approach 1:
The waveguide pattern is divided into multiple regions and drawn on separate photomasks. Each photomask contains a portion of the overall circuit pattern, allowing large-scale optical circuits to be manufactured by combining multiple photomasks. The joint regions are specifically designed to facilitate accurate alignment and connection between these segmented patterns.
Solution Approach 2:
Joint regions are introduced at specific locations where photomasks connect. These joint regions have different characteristics from normal waveguide regions - they are designed with overlapping patterns and width transitions to accommodate alignment variations. This local modification ensures that misalignment errors do not propagate throughout the entire circuit but are contained and compensated at connection points.
2Loss of energy
If joint regions with width changes are introduced to connect waveguides, then optical loss is reduced, but the area of the joint region increases
Solution Approach 1:
Instead of abrupt width changes at joint regions, the patent employs tapered or curved width transitions. The waveguide width gradually changes from the narrow waveguide width to the wider joint region width, creating a smooth transition that minimizes optical reflection and scattering losses. This curved transition profile reduces optical loss while keeping the joint region area compact.
Solution Approach 2:
The joint region width is designed to dynamically transition between different widths along the propagation direction. The width varies continuously rather than remaining constant, creating an adaptive structure that optimizes optical coupling between adjacent waveguides while minimizing the spatial extent of the joint region.
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 significantly reduces losses at joint portions even with low alignment accuracy, maintaining low optical loss and minimizing the area required for the joint region.
Implementation Method 1
the optical circuit pattern on the photomask is transferred to the photoresist 13 in exposure/development steps
Implementation Method 2
using the pattern-transferred photoresist 14 as a mask material, the core layer 12 is subjected to etching processing to form a waveguide core 15
Data Source
AI summary
In an optical circuit divided into a plurality of partial circuits, an optical waveguide having a low optical loss at a connection portion is provided. A photomask in which a waveguide pattern of an optical circuit is divided into a plurality of regions and drawn, the photomask including a waveguide pattern for drawing a joint region in which a waveguide width changes as a waveguide goes toward an outer peripheral portion, to connect a plurality of the waveguides divided and drawn to each other, in which the waveguides are connected to each other by overlapping the joint regions of two of the photomasks and performing exposure.