Waveguide Scatterer Arrays for High-Angle Light Deflection
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Solution Overview
Problem
Existing grating devices face inefficiencies in deflection angles above 20° due to shadowing and high aspect ratio structures, and struggle with phase discretization and absorption losses at optical frequencies, limiting their operational bandwidth and sensitivity to incident beam angles.
Innovation Solution
The use of non-resonating or weakly resonating grating elements with low aspect ratio waveguides that control radiation patterns through interference between guided and radiative components, allowing for large deflection angles and minimal absorption losses, and are designed to be insensitive to incident beam angle variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional diffraction gratings are used to achieve deflection angles above 20°, then the deflection capability is improved, but the diffraction efficiency deteriorates due to shadowing from saw-tooth topology
Solution Approach 1:
The grating structure is segmented into multiple discrete phase elements (waveguides) arranged in a periodic array. Each waveguide acts as an independent phase-modulating element, allowing the grating to achieve large deflection angles through constructive interference without the shadowing effects that plague continuous saw-tooth structures. The segmentation enables efficient light coupling into the desired diffraction order even at deflection angles exceeding 40°.
Solution Approach 2:
Dielectric waveguides serve as intermediary structures that mediate between the incident light and the desired diffraction pattern. These waveguides provide controlled phase delays to the incident light, enabling precise directional control of the diffracted beams. The waveguide intermediary allows for efficient energy transfer to the target diffraction order while minimizing losses to other orders, resolving the contradiction between large deflection angles and high diffraction efficiency.
2Manufacturing precision
If binary-blazed gratings are used to concentrate the field inside the dielectric structure, then the phase control capability is improved, but the aspect ratio of structures increases making fabrication difficult
Solution Approach 1:
The invention changes the operational parameters of the grating elements from resonant to non-resonant or weakly resonant regimes. This parameter change allows for reduced waveguide lengths and lower aspect ratios while maintaining effective phase control capability. The non-resonant operation broadens the operational bandwidth and reduces sensitivity to fabrication tolerances, enabling practical implementation with standard fabrication techniques.
Solution Approach 2:
The patent transitions from two-dimensional planar phase elements to three-dimensional waveguide structures that extend vertically through the substrate. This dimensional change allows for enhanced light-matter interaction and improved phase control without requiring high aspect ratios. The waveguides confine light in the vertical dimension, enabling efficient phase modulation with moderate structural heights.
3Measurement precision
If plasmonic resonators are used for fine phase discretization, then the phase control precision is improved, but absorption losses increase due to ohmic metal losses
Solution Approach 1:
The invention employs composite dielectric structures consisting of multiple materials with different refractive indices arranged in vertical stacks. This composite approach enables fine phase discretization through interference effects between guided and radiative modes, achieving precision comparable to plasmonic resonators without the associated ohmic losses. The dielectric composite materials provide the necessary phase control while maintaining negligible absorption losses.
4Loss of energy
If dielectric resonators are used to avoid absorption losses, then the absorption loss is reduced, but the lateral dimensions increase restricting phase discretization
Solution Approach 1:
The patent exploits the vertical dimension by implementing multi-layer dielectric waveguide structures stacked perpendicular to the substrate plane. This vertical stacking enables fine phase discretization without increasing the lateral footprint of individual grating elements. The guided modes in the vertical dimension provide the necessary phase control, while the compact lateral dimensions allow for dense grating periods and fine angular discretization.
Solution Approach 2:
Different regions of the waveguide structure are assigned different local properties through varying the thickness and material composition of individual layers. This local quality variation enables precise control of the phase profile across the grating aperture, achieving fine phase discretization with compact lateral dimensions. Each layer contributes differently to the overall phase delay, allowing for flexible phase engineering without increasing lateral size.
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 enables efficient directional scattering with high diffraction efficiency and large operational bandwidth, effectively addressing the limitations of conventional gratings by achieving deflection angles exceeding 40° with minimal absorption losses and reduced sensitivity to incident angle changes.
Implementation Method 1
diffraction gratings have been used to periodically modulate the phase of incident light to achieve deflection and dispersion into desired directions
Implementation Method 2
The physical mechanism behind the grating devices described herein relies on the control of the radiation pattern using interference between multiple guided and/or radiative components of light
Data Source
AI summary
There is provided a scattering element comprising a vertically-oriented waveguide comprising one or more dielectric components configured to provide directional scattering of an incident electromagnetic wave in a pattern caused by one of interference between at least two guided components and interference between at least one guided component and at least one radiative component, the guided and radiative components excited by the incident electromagnetic wave. A grating device for transmission or reflection of incident electromagnetic waves in a desired direction, the grating device comprising an array of the scattering elements, is also provided.