Crystal Body Dislocation Density Ratio for Faraday Rotator Birefringence
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Solution Overview
Problem
Existing crystal bodies used in optical devices, such as Faraday rotators, often fail to achieve a satisfactory extinction ratio due to high dislocation densities in both light passing and side surfaces, leading to birefringence and poor polarization conversion.
Innovation Solution
A crystal body with a specific dislocation density ratio between light passing surfaces and side surfaces, within the range of 1 to 3600, is developed to minimize birefringence and enhance extinction ratio, achieved through careful polishing and grinding processes to remove surface layer dislocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If outer periphery grinding process is performed on outer peripheral surface, then shaping is achieved, but dislocations are introduced causing residual stress and birefringence
Solution Approach 1:
The patent segments the surface treatment process into distinct zones: the outer peripheral surface undergoes grinding for shaping, while the light passing surfaces undergo polishing for low dislocation density. This spatial segmentation allows each surface to have optimized properties for its specific function.
Solution Approach 2:
The patent applies different surface treatment qualities to different locations: the outer peripheral surface is ground to achieve precise shape, while the light passing surfaces are polished to achieve low dislocation density. This local quality differentiation resolves the contradiction between shaping requirements and dislocation reduction.
2Object-affected harmful factors
If polishing process is performed on both end surfaces, then dislocation density is greatly reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies polishing selectively only to the light passing surfaces where low dislocation density is critical, rather than polishing all surfaces uniformly. This partial action approach reduces manufacturing complexity while maintaining optical performance.
3Ease of manufacture
If high dislocation density exists in both light passing and side surfaces, then manufacturing is easier, but extinction ratio deteriorates due to birefringence
Solution Approach 1:
The patent implements local quality control by differentiating surface treatment based on functional requirements: light passing surfaces receive polishing treatment to achieve low dislocation density for high extinction ratio, while side surfaces can have higher dislocation density as they do not affect optical performance. This resolves the contradiction between manufacturing ease and extinction ratio.
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 solution effectively reduces birefringence and improves the extinction ratio, ensuring better polarization conversion and optical performance in devices like Faraday rotators and other optical applications.
Implementation Method 1
In optical devices such as a Faraday rotator, a polarizer, a wavelength conversion element, a laser crystal, a lens, a wavelength plate, a beam splitter, an electro-optic element, and an acousto-optic device, a crystal body constituted by a crystal is used
Implementation Method 2
Herein, the dislocations cause birefringence in the light passing surfaces of the Faraday rotator
Data Source
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AI summary
The present invention is a crystal body constituted by a crystal and having a pair of light passing surfaces which face each other and pass light and at least one side surface which connects the pair of the light passing surfaces. In the crystal body according to the present invention, a ratio B/A of a dislocation density A (number/cm2) in the light passing surfaces and a dislocation density B (number/cm2) in the side surface satisfies the following general formula. 1≤B/A≤3600