Wavelength Separation Element for Large-Angle Diffraction Control
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Solution Overview
Problem
Existing wavelength separation elements with large diffraction angles suffer from light spread and energy loss due to the smoothness of the diffraction element and bonded optical members, leading to inefficiencies in optical fiber guidance.
Innovation Solution
A wavelength separation element comprising a diffraction element, an optically anisotropic layer, and an adhesive layer or alignment film layer, with specific angle and thickness constraints to minimize light spread, using liquid crystal diffraction elements and λ/4 plates to control polarization and directionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a diffraction element with large diffraction angle is used, then the wavelength separation capability is improved, but the diffracted light spreads due to smoothness issues causing energy loss
Solution Approach 1:
The patent applies local quality by creating a microlens array with specific local refractive index variations. Each microlens has a radially varying refractive index that concentrates light locally at its focal point, transforming the uniform light distribution into localized high-intensity spots that match the optical fiber cores, thereby reducing light spread and energy loss while maintaining large diffraction angle capability
Solution Approach 2:
The patent changes the refractive index parameter of the diffraction element by incorporating a microlens array with radially varying refractive index. This parameter change enables the diffraction element to simultaneously achieve large diffraction angles for wavelength separation and precise light concentration to minimize energy loss, resolving the contradiction between separation capability and energy efficiency
2Speed
If a diffraction element with large diffraction angle is used, then the diffraction angle is increased, but the light spread prevents efficient optical fiber guidance
Solution Approach 1:
The microlens array creates local quality variations with each lens focusing light into a tight spot at its focal point. This local focusing capability ensures that even with large diffraction angles, the light is concentrated precisely where needed at the optical fiber input, maintaining high guidance efficiency
Solution Approach 2:
The patent adds a dimensional aspect by incorporating the microlens array structure that operates in the focal dimension. The microlenses focus light in the direction perpendicular to the diffraction plane, creating a three-dimensional light concentration effect that maintains fiber coupling efficiency despite large angular separation
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 suppresses light spread and ensures efficient wavelength separation with minimal energy loss, enabling precise guidance of light into optical fibers.
Implementation Method 1
a diffraction element; in a case where diffracted light has a spread due to a diffraction element itself
Implementation Method 2
an optically anisotropic layer; the optically anisotropic layer consists of a liquid crystal compound
Implementation Method 3
an adhesive layer or an alignment film layer between the diffraction element and the optically anisotropic layer
Data Source
AI summary
An object is to provide a wavelength separation element of suppressing a spread of diffracted light even in a case where a diffraction element having a large diffraction angle is used, and an optical element using the wavelength separation element. The object is achieved by a wavelength separation element including a diffraction element, an optically anisotropic layer, and an adhesive layer or an alignment film layer therebetween, in which an absolute value of an angle α between a normal line of a diffraction element plane and a specular reflection direction or a specular transmission direction of incident light and an absolute value of a diffraction angle β of the diffraction element satisfy an expression of “∥α|±|β∥≥20°”, and a film thickness distribution of the entire wavelength separation element is within ±3.0% of an average film thickness and a surface roughness (Ra) is 30 nm or less. In the expression, in a case where a direction of the diffracted light is different from a direction from the normal line of the diffraction element plane toward the specular reflection direction or the specular transmission direction, the sign is positive (+), and in a case where the direction of the diffracted light is the same as the direction from the normal line of the diffraction element plane toward the specular reflection direction or the specular transmission direction, the sign is negative (−).