Single-Layer Diffractive Optical Element with Gradient Refractive Index
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Solution Overview
Problem
Existing diffractive optical elements with long periods relative to the wavelength of light suffer from significant reduction in diffraction efficiency when the wavelength deviates from the design wavelength, leading to unwanted stray light and limitations in broadband optical systems.
Innovation Solution
A single-layer diffractive optical element with a spatial variation in refractive index, forming a gradient index structure, is designed to achieve high diffraction efficiency across a broad spectral range by optimizing the maximum and minimum refractive indices, Abbe numbers, and partial dispersions within each section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single-layer diffractive optical element with long period is used to achieve high diffraction efficiency at design wavelength, then diffraction efficiency at design wavelength is improved, but diffraction efficiency deteriorates significantly when wavelength deviates from design wavelength
Solution Approach 1:
The patent applies local quality by implementing different refractive index profiles in different regions of the diffractive optical element. Specifically, the element comprises a first region with a first refractive index profile and a second region with a second refractive index profile, where each region is optimized for different wavelength ranges. This allows the element to maintain high diffraction efficiency across a broad spectral range by locally adapting the optical properties to suit different wavelength requirements.
Solution Approach 2:
The patent employs composite materials by combining multiple materials with different dispersion characteristics in a single diffractive optical element. The element uses a first material with a first dispersion characteristic and a second material with a second dispersion characteristic, creating a composite structure that achieves efficiency achromatization. This composite approach enables the element to compensate for wavelength-dependent efficiency variations by leveraging the complementary dispersion properties of different materials.
2Adaptability or versatility
If multi-layer diffractive optical elements are used to achieve efficiency achromatization, then spectral range is improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple diffractive layers into a single integrated element. By combining different refractive index profiles and material compositions within one layer, the element achieves efficiency achromatization across a broad spectral range without requiring multiple separate layers. This merging approach simplifies the device structure while maintaining the spectral performance benefits of multi-layer designs.
Solution Approach 2:
The patent implements universality by designing a single diffractive optical element that performs multiple functions simultaneously. The element achieves both diffraction and efficiency achromatization across a broad spectral range within a single structure, eliminating the need for separate specialized layers for different wavelength ranges. This multi-functional design reduces device complexity while maintaining broad spectral adaptability.
3Manufacturing precision
If profile height is reduced to minimize shadowing effects, then manufacturing precision is improved, but diffraction efficiency may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive index profiles and material compositions to achieve high diffraction efficiency with reduced profile heights. By carefully controlling the refractive index variations and material properties, the element maintains effective diffraction performance while minimizing the physical profile height. This reduces shadowing effects and improves manufacturing precision without sacrificing diffraction efficiency.
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 proposed solution achieves an average diffraction efficiency of at least 0.95 over a spectral range of at least 300 nm, maintaining high efficiency with reduced profile height and minimizing shadowing effects, thus enabling efficient use in broadband optical systems.
Implementation Method 1
diffractive optical elements are based on the principle of the diffraction of light waves and are designed to deflect light at a specific wavelength into a specific direction with the aid of a diffractive structure
Implementation Method 2
a diffractive structure with a spatial variation in the refractive index
Data Source
AI summary
The invention relates to a diffractive optical element with a spatial variation in the refractive index, wherein a sequence of adjacent sections, which form a diffractive structure, is formed by the spatial variation in the refractive index, within which sections the refractive index varies in each case. Over a spectral range extending over at least 300 nm, the diffractive structure has a diffraction efficiency of at least 0.95, averaged over the entire spectral range. The value of the diffraction efficiency of at least 0.95, averaged over the entire spectral range, is realized by a single single-layer diffractive structure with an optimized combination of at least two refractive indices and at least two Abbe numbers within each section of the sequence of adjacent sections. The refractive index variation can be achieved by means of doping, material mixing, or structuring into sub-wavelength ranges.