Ridge Waveguide Optical Element Using Direct Bonding
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Solution Overview
Problem
Conventional ridge waveguides face issues with waveguide fluctuations, propagation loss, and material compatibility due to differences in thermal expansion coefficients and non-uniformity, particularly when using dissimilar materials for overcladding layers, which affect optical properties and long-term reliability.
Innovation Solution
The direct bonding method of similar single-crystal substrates, such as Z-cut LT and Zn-doped LN, with a ridge structure and periodically polarization-reversed structure, where the substrates are bonded using thermal diffusion, and a thin film layer is formed on the surface to enhance optical properties and material compatibility, reducing waveguide fluctuations and allowing high-output optical power input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dissimilar materials are used for overcladding layers in ridge waveguides, then material compatibility and thermal expansion differences cause waveguide fluctuations and propagation loss, but using similar single-crystal substrates increases manufacturing complexity
Solution Approach 1:
The patent applies homogeneity by using similar single-crystal substrates (e.g., LiNbO3 and LiTaO3) for both the waveguide core and overcladding layers. This ensures matching thermal expansion coefficients and refractive indices, eliminating waveguide fluctuations and propagation loss caused by material mismatches. The homogeneous material composition throughout the waveguide structure maintains stable optical properties.
Solution Approach 2:
The patent uses direct bonding of single-crystal substrates where the overcladding layer is essentially a copy of the core material composition. This copying approach ensures identical thermal and optical properties between layers, preventing interface-related waveguide instabilities while maintaining manufacturing feasibility through established direct bonding techniques.
2Reliability
If direct bonding method is used for single-crystal substrates, then material compatibility improves, but bonding process precision requirements increase
Solution Approach 1:
The patent employs parameter changes by controlling bonding temperature and pressure conditions during the direct bonding process. By optimizing these parameters, the bonding interface achieves atomic-level contact between single-crystal substrates, ensuring high material compatibility while managing the precision requirements through controlled thermal and mechanical conditions.
3Productivity
If ridge structure with periodically polarization-reversed structure is formed, then wavelength conversion efficiency increases, but waveguide fluctuations due to non-uniformity increase propagation loss
Solution Approach 1:
The patent eliminates waveguide fluctuations by using homogeneous single-crystal materials for the ridge structure. The uniform material composition ensures consistent refractive index and thermal properties throughout the waveguide, preventing non-uniformity-induced propagation loss while maintaining the periodically polarization-reversed structure for efficient wavelength conversion.
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 results in a highly efficient optical element with reduced propagation loss and improved material compatibility, enabling accurate formation of the periodically polarization-reversed structure and supporting high-output optical power input, while maintaining optical properties and long-term reliability.
Implementation Method 1
the substrates are bonded using thermal diffusion
Implementation Method 2
Wavelength conversion elements using second harmonic generation (hereinafter denoted by SHG), difference frequency generation (hereinafter denoted by DFG), sum frequency generation (hereinafter denoted by SFG), and the like achieved by PPLN are known.
Implementation Method 3
difference frequency generation (hereinafter denoted by DFG)
Implementation Method 4
sum frequency generation (hereinafter denoted by SFG)
Implementation Method 5
an optical element using a nonlinear optical effect or an electro-optic effect (EO effect)
Data Source
AI summary
A highly-efficient ridge waveguide includes a base substrate of a single-crystal and a core substrate made of a nonlinear optical medium, the base substrate and the core substrate being directly bonded, and includes a thin film layer formed on a surface of the core substrate on the upper side of a periodically polarization-reversed structure, and becomes a wavelength conversion element. A direct bonding method through thermal diffusion is applied to bonding. The core substrate has a ridge structure formed in a light propagating direction and a reversed structure formed by processing this. A surface of the core substrate is ground and a thin film layer is formed on the ground surface. A core formed by digging a core layer of the core substrate in an unbonded state is provided on an upper surface of an undercladding layer of the base substrate in a bonded state. Two side surfaces of the core are in contact with an air layer.