Optical Modulator Coupling Layer Layout for Etching Variation
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Solution Overview
Problem
Conventional optical modulators face challenges in controlling etching accuracy over large-diameter wafers, leading to in-wafer plane variation in element performance, affecting optical confinement factor, phase of guided light, and optical loss.
Innovation Solution
The optical modulator design includes a cladding layer, a semiconductor layer, a phase modulation layer, and an optical coupling layer formed separately from the semiconductor layer, using materials with high etching selectivity to reduce processing variations, and shifting the optical coupling layer's position to minimize light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rib-type optical waveguide structure is formed by etching a group III-V compound semiconductor layer, then the manufacturing process is simplified and epitaxial growth is unnecessary, but the optical confinement factor, phase of guided light, and optical loss sensitively change due to etching amount variation across the wafer surface
Solution Approach 1:
A dummy rib structure is introduced as an intermediary element during the etching process. This dummy rib acts as a reference marker that allows precise control of the etching depth and position. By using the dummy rib as a mediator between the patterning process and the final optical waveguide formation, the invention achieves accurate rib formation without sensitive variation in optical characteristics across the wafer surface.
2Device complexity
If the optical coupling layer is integrated with the semiconductor layer, then the device structure is compact, but in-wafer plane variation in element performance occurs due to etching inaccuracies
Solution Approach 1:
The optical coupling layer is segmented from the semiconductor layer, forming a separate structure that is optically coupled but physically distinct. This segmentation allows the optical coupling layer to be formed independently with high precision, avoiding the etching variations that affect the semiconductor layer. The separate formation of the optical coupling layer ensures consistent element performance across the wafer while maintaining overall device compactness.
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 design suppresses in-wafer plane variation, achieving high optical confinement and low optical loss, resulting in a low-loss and high-efficiency optical modulator.
Implementation Method 1
an optical coupling layer that is stacked on the semiconductor layer separately from the semiconductor layer and extends along the phase modulation layer in a state of being optically couplable with the phase modulation layer
Data Source
AI summary
The optical modulator first includes a lower cladding layer formed on a substrate and a semiconductor layer formed of a group III-V compound semiconductor and disposed on the lower cladding layer. In the semiconductor layer, a phase modulation layer extending in a predetermined direction, and an n-type layer and a p-type layer formed in contact with the phase modulation layer with the phase modulation layer interposed therebetween in plan view are formed. In addition, the optical modulator includes an optical coupling layer that is stacked on the semiconductor layer separately from the semiconductor layer and extends along the phase modulation layer in a state of being optically couplable with the phase modulation layer.