Wavelength Conversion Waveguide Fabrication with Local QPM Adjustment
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Solution Overview
Problem
Conventional wavelength conversion elements face issues with processing errors and non-uniform film thickness distribution, leading to variations in optical characteristics and reduced efficiency due to difficulties in adjusting the quasi-phase matching condition, which are challenging to correct through temperature control.
Innovation Solution
A manufacturing method that allows for local adjustment of the polarization inversion period of the optical waveguide core by optimizing the arrangement of periodic polarization inversion regions and fabrication processes, enabling precise control of the quasi-phase matching condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical waveguide core is formed by conventional ridge-type fabrication methods, then the light confinement effect is improved, but the polarization inversion period cannot be adjusted and controlled in subsequent processes
Solution Approach 1:
The patent divides the fabrication process into distinct stages: first forming the periodic polarization inversion structure in the bulk crystal, then bonding substrates, and finally forming the optical waveguide core. This segmentation allows the polarization inversion period to be determined and adjusted independently during the crystal processing stage, while the waveguide formation stage optimizes light confinement. The separation of these functions resolves the contradiction by enabling both adjustable polarization periods and effective light confinement.
2Power
If the film thickness of the nonlinear optical crystal is reduced to 20m to achieve high power density, then the power density in the optical waveguide is improved, but the film thickness distribution becomes non-uniform causing variations in optical characteristics
Solution Approach 1:
The patent performs preliminary actions by forming the periodic polarization inversion structure and determining the polarization inversion period before bonding and waveguide formation. This allows the polarization characteristics to be established when the crystal is still in a more uniform state, before subsequent processing introduces thickness variations. The preliminary establishment of the polarization structure compensates for later non-uniformities in film thickness.
3Reliability
If temperature control is used to correct quasi-phase matching conditions, then the wavelength conversion efficiency can be adjusted, but the correction capability is limited and cannot address local variations
Solution Approach 1:
The patent applies local quality by allowing different regions of the optical waveguide core to have different polarization inversion periods. By controlling the polarization inversion period locally during the fabrication process, each region can be optimized for its specific function and wavelength requirements. This local control capability far exceeds the limited global adjustment possible through temperature control, enabling precise optimization of wavelength conversion efficiency across different operating conditions.
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 method enhances the optical characteristics of wavelength conversion elements by stabilizing the optical spectrum distribution and improving wavelength conversion efficiency, addressing the limitations of conventional methods.
Implementation Method 1
A wavelength conversion element used in a wavelength conversion device is realized by using an optical crystal or the like having a second-order nonlinear effect
Implementation Method 2
an optical waveguide utilizing periodically poled lithium niobate (hereinafter, referred to as PPLN) is attracting attention as an element that can achieve high wavelength conversion efficiency by increasing a light intensity and using a quasi-phase matching technique
Implementation Method 3
heat is applied to the first substrate and the second substrate to perform diffusion bonding
Data Source
AI summary
A manufacturing method for a wavelength conversion element, including: a first process of forming an optical waveguide core substrate having one or more periodic polarization inversion region with a second-order nonlinear effect; a second process of bonding the optical waveguide core substrate to a substrate having a refractive index lower than a refractive index of the optical waveguide core substrate in a range of used light wavelengths to form a bonded substrate, and thinning the optical waveguide core substrate to form a core layer; and a third process of processing the core layer of the bonded substrate to form an optical waveguide core, wherein, in the third process, a polarization inversion period of a periodic polarization inversion structure of the formed optical waveguide core is adjusted at least locally by selecting a formation position of the optical waveguide core with respect to the one or more periodic polarization inversion region.