Subwavelength Diffractive Component Wide Spectral Band Efficiency
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Solution Overview
Problem
Conventional diffractive optical elements exhibit low diffraction efficiency over a wide spectral band due to weak dispersion of materials, leading to parasitic light and reduced image quality in optical systems, particularly in applications requiring a broad spectral range.
Innovation Solution
A subwavelength diffractive component with multiple elementary areas, each having microstructures that form an artificial material with varying effective indices, allowing for efficient diffraction across a wide spectral band by optimizing the blaze condition and surface area weighting to enhance diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diffractive elements with single blaze wavelength are used, then diffraction efficiency is optimized at a specific wavelength, but diffraction efficiency drops significantly across a wide spectral band
Solution Approach 1:
The diffractive element is divided into multiple zones, each zone having a different blaze wavelength optimized for a specific portion of the spectral band. This segmentation allows each zone to efficiently diffract wavelengths within its optimized range, collectively covering the entire broad spectral band with high efficiency across all zones
Solution Approach 2:
Different regions of the diffractive element are assigned different optical properties (blaze wavelengths) according to the local spectral requirements. Each zone's structure is locally optimized for its specific blaze wavelength, creating a gradient or stepped distribution of blaze wavelengths across the element surface to match the desired spectral response
2Ease of manufacture
If material dispersion is weak, then material is easy to work with and manufacture, but parasitic light increases and diffraction efficiency decreases
Solution Approach 1:
The patent employs composite or effective medium structures where multiple materials with different dispersion properties are combined, or where a structured array of subwavelength elements creates an effective material with enhanced dispersion characteristics. This composite approach maintains manufacturability while achieving the strong dispersion needed to reduce parasitic light and improve diffraction efficiency
3Reliability
If single blaze order optimization is pursued, then efficiency in one order is maximized, but light is lost to higher orders creating parasitic light
Solution Approach 1:
The patent optimizes multiple parameters simultaneously including the blaze wavelength, zone dimensions, and relative weighting of different zones to control the distribution of diffracted light. By carefully adjusting these parameters, the design maximizes efficiency in the desired blaze order while minimizing coupling to higher orders that would create parasitic light
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 component achieves improved diffraction efficiency and design flexibility, enabling efficient light or radiofrequency beam manipulation across a broader spectral range, surpassing the limitations of conventional diffractive elements.
Implementation Method 1
The diffraction process does not consist of a simple transmission or reflection of an incident beam, light or microwave, in a new direction different from that of the incident beam: the incident beam is split up into several beams, each redirected at a different angle according to different orders of diffraction.
Implementation Method 2
an elementary area of type i comprising a plurality of microstructures respectively having at least a size less than 1.5 times the blaze wavelength of index i, the microstructures being arranged to form an artificial material exhibiting an effective index variation
Data Source
AI summary
A wideband diffractive component diffracting an incident beam exhibiting a wavelength in a diffraction spectral band is provided. The diffractive component elementary areas are arranged on a surface, each area belonging to a type indexed by an index i lying between 1 and n, with n greater than 1, corresponding to blaze wavelength λi of index i, the blaze wavelengths lying in the diffraction spectral band. An elementary area of type i includes microstructures sized less than 1.5 times the blaze wavelength of index i, arranged to form an artificial material exhibiting an effective index variation where an elementary area of type i constitutes a blazed diffractive element at the blaze wavelength λi of index i, the different values of the blaze wavelengths and the proportion of surface area occupied by the areas of a given type a function of a global diffraction efficiency desired in the diffraction spectral band.