Diffractive Optical Element with Anti-Reflection Features
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Solution Overview
Problem
Diffractive optical elements face challenges in reducing reflection efficiently over a wide range of wavelengths and require additional coatings, which increase complexity and cost, while traditional refractive elements are bulky and inefficient in volume usage.
Innovation Solution
The integration of diffractive focusing features and anti-reflection features on a single surface with varying duty cycles and depths, etched into a transparent material like silicon or germanium, to achieve an effective refractive index that minimizes reflection without additional coatings, allowing for efficient light focusing and reduced volume occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional anti-reflection coatings are applied to diffractive optical elements, then reflection is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the anti-reflection function with the diffractive focusing features by integrating etched structures into the same optical surface. The diffractive features serve dual purposes: focusing light and reducing reflection through their specific geometric patterns and depth variations, eliminating the need for separate anti-reflection coatings.
Solution Approach 2:
The diffractive optical element's own surface structures provide the anti-reflection function. By designing the diffractive features with specific depths and duty cycles, the element itself generates the phase shifts needed to reduce reflection, making the system self-sufficient without external coatings.
2Reliability
If diffractive features are etched deeper into the substrate, then focusing performance improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies different etch depths to different regions of the diffractive features. By varying the depth locally across the optical surface while maintaining a maximum depth constraint, the design achieves optimal focusing performance in critical areas while keeping manufacturing within feasible limits for standard processes.
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 solution effectively reduces reflections across a broad wavelength range, enhances light transmission, and simplifies manufacturing by using standard semiconductor processes, resulting in a compact and cost-effective optical element.
Implementation Method 1
diffractive focusing features that extend into the body, the diffractive focusing features having a same first depth that is greater than the wavelength
Implementation Method 2
an effective refractive index of the diffractive focusing features and the diffractive anti-reflection features, together, is less than or equal to a specified value
Implementation Method 3
diffractive anti-reflection features that extend into the body, the diffractive anti-reflection features having a same second depth that is less than the wavelength
Implementation Method 4
an effective refractive index of the diffractive focusing features and the diffractive anti-reflection features, together, is less than or equal to a specified value
Data Source
AI summary
In an optical element, diffractive focusing features and diffractive anti-reflection features can extend into a first surface of a body, such as by etching. The diffractive focusing features can have a same first depth that is greater than a wavelength, and can be located in a first area to have a duty cycle that varies over the first area. The diffractive anti-reflection features can have a same second depth that is less than the wavelength. In some examples, an effective refractive index of the diffractive focusing features and the diffractive anti-reflection features, together, can be less than or equal to a specified value, such as 120% of a square root of a refractive index of a material of the body. In other examples, the diffractive anti-reflection features can be located in the first area to have a duty cycle that is constant over the first area.