Vertical PN Silicon Modulator Waveguide Design
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Solution Overview
Problem
Silicon modulators face challenges in achieving high modulation efficiency while minimizing optical loss, as heavy doping for quick state switching and low resistance often results in reduced optical signal quality due to increased electrical resistance and optical loss.
Innovation Solution
A vertical PN junction design is employed, where small areas of heavy doping at the center of the waveguide core enhance modulation efficiency, while larger areas of lighter doping reduce optical loss by minimizing the doping contribution outside the depletion region, allowing for efficient modulation with reduced power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If horizontal surface-emitting modulators are used, then they are well-suited for integrated circuits, but they require 90-degree bends in the waveguide to change signal direction
Solution Approach 1:
The patent transitions from horizontal surface-emitting modulators to vertical edge-emitting modulators, changing the emission dimension from horizontal to vertical. This allows the light signal to travel vertically through the waveguide without requiring 90-degree bends, simplifying the waveguide structure while maintaining integration capability
2Ease of operation
If vertical edge-emitting modulators are used, then alignment between laser diode and modulator is easier, but conventional vertical modulators have high insertion loss due to mode mismatch
Solution Approach 1:
The patent creates a localized region with different refractive index characteristics by forming a first cladding layer with higher refractive index than the second cladding layer. This local quality change in the waveguide structure enables single-mode propagation, reducing mode mismatch and insertion loss while maintaining the vertical edge-emitting configuration that provides alignment advantages
3Ease of operation
If conventional vertical modulators are used, then alignment is improved, but they exhibit high insertion loss and difficulty achieving single-mode operation
Solution Approach 1:
The patent changes the refractive index parameter distribution within the waveguide by using cladding layers with different refractive indices (first cladding layer with higher index, second cladding layer with lower index). This parameter change enables the waveguide to support only the fundamental mode, achieving reliable single-mode operation while maintaining vertical edge-emitting alignment advantages
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 vertical PN junction design achieves high modulation efficiency with low optical loss, enabling fast state switching and reduced power consumption, while maintaining a compact device size.
Implementation Method 1
a waveguide configured to receive an optical signal from a laser diode positioned at a second end of the substrate and to convey the optical signal vertically across the substrate in a vertical direction
Implementation Method 2
Vertical pn silicon modulator
Data Source
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AI summary
A silicon waveguide (110) comprising a waveguide core (118) that comprises a first positively doped region (111), also refers to as P1 region, vertically adjacent to a second positively doped region (112), also refers to as P2 region, The P2 region (112) is more heavily positively doped than the P1 region (111). A first negatively doped region (114), also refers to as N1 region, is vertically adjacent to a second negatively doped region (113), and also refers to as N2 region. The N2 region (113) is more heavily negatively doped than the N1 region (114). The N2 region (113) and the P2 region (112) are positioned vertically adjacent to form a PN junction. The N1 region (114), the N2 region (113), the P1 region (111), and the P2 region (112) are positioned as a vertical PN junction and configured to completely deplete the P2 region (112) of positive ions and completely deplete the N2 region (113) of negative ions when a voltage drop is applied across the N1 region (114), the N2 region (113), the P1 region (111), and the P2 region (112).