Lithium Niobate Optical Control Element Hydroxyl Group Control
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Solution Overview
Problem
In high-integrated lithium niobate optical modulators, the variation of mode field diameter (MFD) and optical loss are significant due to the influence of moisture in the diffusion atmosphere, particularly when the pattern width of the titanium film is 6 μm or less, leading to instability and increased loss.
Innovation Solution
An optical control element with a titanium film pattern width of 6 μm or less and a lithium niobate substrate thickness of 20 μm or less, where the amount of hydroxyl groups absorbed into the substrate is controlled within a range of 0.5 to 2.5 cm−1, effectively stabilizing MFD and reducing optical loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pattern width of the titanium film is reduced to 6 μm or less to enable high integration, then the optical confinement efficiency decreases and MFD broadens, but this enables higher integration of optical modulation circuits
Solution Approach 1:
The patent changes the chemical composition parameters of the diffusion atmosphere by controlling hydroxyl group concentration (0.5 to 2.5 cm⁻¹) and moisture content (dew point -30°C to 0°C). This parameter change stabilizes the refractive index distribution in the optical waveguide, thereby controlling MFD even when the titanium film pattern width is reduced to 6 μm or less for high integration
Solution Approach 2:
The patent creates a controlled inert-like diffusion atmosphere by precisely controlling moisture content and hydroxyl group concentration. This controlled atmosphere prevents unwanted chemical reactions and stabilizes the diffusion process, enabling precise MFD control in highly integrated structures with narrow titanium films
2Loss of energy
If the pattern width of the titanium film is reduced to 6 μm or less to improve optical loss, then MFD variation increases significantly due to moisture influence, but this can reduce optical loss if MFD is controlled
Solution Approach 1:
The patent optimizes the diffusion atmosphere parameters by controlling hydroxyl group concentration (0.5 to 2.5 cm⁻¹) and moisture content (dew point -30°C to 0°C). This parameter optimization stabilizes the diffusion process and refractive index distribution, reducing MFD variation while maintaining narrow titanium film width (6 μm or less) to minimize optical loss
3Stability of the object's composition
If the amount of moisture in the electric furnace is increased to suppress Li diffusion, then optical confinement improves, but MFD variation increases and optical loss increases when titanium film width is 6 μm or less
Solution Approach 1:
The patent optimizes the moisture content parameter by controlling dew point temperature (-30°C to 0°C) and hydroxyl group concentration (0.5 to 2.5 cm⁻¹). This optimized parameter balance suppresses Li diffusion to maintain optical confinement while preventing excessive MFD variation and optical loss that occur with higher moisture levels
Solution Approach 2:
The patent creates a controlled low-moisture diffusion atmosphere that acts as a stable environment. This controlled atmosphere suppresses unwanted Li diffusion while maintaining consistent diffusion conditions, thereby achieving both optical confinement and MFD stability in highly integrated optical control elements
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 configuration suppresses MFD variation and minimizes optical loss by optimizing the absorption of hydroxyl groups and moisture levels in the process gas, ensuring stable and efficient optical performance.
Implementation Method 1
an optical waveguide formed by using diffusion of titanium that is formed on a lithium niobate substrate
Implementation Method 2
an amount of a hydroxyl group absorbed into the lithium niobate substrate is set to be in a range of 0.5 to 2.5 cm−1 in terms of absorption coefficient
Data Source
AI summary
An optical control element including an optical waveguide formed by using diffusion of titanium that is formed on a lithium niobate substrate and a control electrode formed on the lithium niobate substrate that is provided in the vicinity of the optical waveguide, in which an amount of a hydroxyl group absorbed into the lithium niobate substrate is set to be in a range of 0.5 to 2.5 cm−1.