Wavelength-Dependent Diffraction Grating for Beam Redirection
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Solution Overview
Problem
Diffraction gratings used for beam redirection in multi-wavelength applications suffer from spatial separation of wavelength sub-beams due to their dependence on wavelength, which is undesirable in beam steering and coupling applications.
Innovation Solution
A diffraction grating design with multiple grating structures having wavelength-dependent spatial variations in optical permittivity, allowing for controlled diffraction angles of different color components to be equal, enabling efficient guiding of white-light beams without dispersing them into individual color sub-beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional diffraction grating is used for beam redirection, then the beam can be redirected at oblique angles with space efficiency, but the wavelength sub-beams become spatially separated due to wavelength-dependent diffraction angles
Solution Approach 1:
The diffraction grating is segmented into multiple independent grating structures, each designed with a specific grating period to diffract a particular wavelength range at the desired oblique angle. This segmentation allows each grating structure to handle specific wavelengths independently, preventing spatial separation of wavelength sub-beams while maintaining space-efficient oblique redirection
Solution Approach 2:
Different regions of the diffraction grating are assigned different local properties (grating periods) optimized for specific wavelength ranges. The grating period is locally adjusted so that each region diffracts its target wavelength at the same oblique angle, ensuring all wavelength sub-beams remain coupled while achieving space-efficient redirection
2Device complexity
If a single grating period is used for all wavelengths, then the grating structure is simple, but the diffraction angles vary with wavelength causing spatial separation
Solution Approach 1:
The grating is divided into multiple segments with different grating periods, where each segment is optimized for a specific wavelength range. This segmentation maintains relative structural simplicity within each segment while achieving wavelength-independent diffraction angles across the full spectrum through coordinated design of multiple segments
Solution Approach 2:
The diffraction grating is designed with multi-functionality to handle multiple wavelength ranges simultaneously. Each grating structure serves multiple purposes: diffracting its specific wavelength range at the correct angle while also acting as a transparent or non-diffracting element for other wavelength ranges, thus maintaining beam coupling efficiency across the full spectrum
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 design allows for compact optical systems to guide white-light beams with minimal dispersion, expanding the viewing angle and wavelength range, and improving color range fidelity and uniformity in display systems.
Implementation Method 1
Diffraction gratings are optical devices for separating light at different wavelengths by using the phenomenon of optical diffraction on a periodic or quasi-periodic grating structure. The angle of diffraction of light depends on the ratio of the wavelength of light to the period of the periodic or quasi-periodic grating structure
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A diffraction grating with independently controlled diffraction angles for optical beams at different wavelengths may be used to redirect and couple light to a waveguide in an efficient, space-saving manner. The diffraction grating can include a layer with optical permittivity and associated index contrast of the grating grooves at different grating periods dependent on wavelength.