Optical Waveguide Slope Change Structure for Lower Voltage and Loss
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Solution Overview
Problem
Optical modulators using lithium niobate waveguides face challenges with high driving voltage and increased propagation loss due to non-ideal cross-sectional shapes and narrow upper portions, leading to light leakage and scattering.
Innovation Solution
The optical waveguide is designed with a side surface featuring at least one slope change point to approximate a circular cross-section, reducing driving voltage and propagation loss by narrowing the upper portion while maintaining efficient light guidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the upper portion of the optical waveguide is narrowed to concentrate the electric field, then the driving voltage is reduced, but light leakage increases and propagation loss increases
Solution Approach 1:
The side surface of the optical waveguide is designed with a curved shape featuring at least one slope change point, transitioning from a straight-sided structure to a curved profile. This curvature approximates a circular cross-section, which reduces light leakage at corners while maintaining the narrowed upper portion for electric field concentration, thereby simultaneously reducing both driving voltage and propagation loss
Solution Approach 2:
The slope angle of the side surface is optimized to be 45 degrees or more, creating a specific geometric parameter that balances electric field concentration and light guidance. This parameter change in the side surface angle enables the waveguide to achieve low driving voltage while preventing excessive light leakage
2Ease of manufacture
If the cross-section of the optical waveguide is made trapezoidal or quadrilateral for ease of manufacture, then manufacturing is simplified, but light leaks to corners and propagation loss increases
Solution Approach 1:
The side surface is designed with curvature and slope change points to approximate a circular cross-section, eliminating the sharp corners of traditional trapezoidal waveguides that cause light leakage. This curved profile reduces propagation loss while remaining compatible with dry etching processes through controlled slope angles
3Ease of manufacture
If the side surface of the optical waveguide is made straight for simple manufacturing, then fabrication is easier, but the cross-section deviates from ideal circular shape and propagation loss increases
Solution Approach 1:
The side surface incorporates curvature with at least one slope change point, creating a profile that approximates a circular cross-section. This curved design improves light guidance and reduces propagation loss while being manufacturable through dry etching with appropriate slope angle control
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 effectively reduces driving voltage and propagation loss, enhancing the efficiency and performance of optical modulators by minimizing light leakage and scattering.
Implementation Method 1
an optical waveguide with a ridge portion having a cross-sectional shape that approximates a circle when viewed in a propagation direction of light
Implementation Method 2
an optical modulator using an optical waveguide formed of lithium niobate (LiNbO3)
Data Source
AI summary
An electro-optical device includes a substrate, an optical waveguide formed on the substrate, a buffer layer formed on the substrate which is provided so as to cover the optical waveguide and an electrode formed on the buffer layer, when viewed in a propagation direction of light, a side surface of the optical waveguide has at least one slope change point. An electro-optical device can reduce the driving voltage and the propagation loss of light.