Planar Optical Devices Using Sub-Wavelength Diffraction Gratings
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Solution Overview
Problem
Conventional optical devices face challenges in minimizing beam width or spot size due to the cost and complexity of fabricating high numerical aperture lenses and compatibility issues with planar integrated circuits, while existing focusing grating couplers are limited in coupling light from free space to free space.
Innovation Solution
The development of planar optical devices using sub-wavelength diffraction gratings configured between reflective structures to control the phase front of transmitted light, allowing these devices to operate as conventional optical elements like convex lenses, concave lenses, or prisms, using conventional lithography and etching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional convex lenses are used to minimize beam width, then spot size is reduced, but manufacturing cost and complexity increase due to difficulty in fabricating small lenses with large curvatures and precise polishing requirements
Solution Approach 1:
The patent replaces conventional mechanical lenses with a diffraction grating-based optical system. The grating structure uses periodic patterns to achieve beam focusing and shaping through diffraction effects rather than refractive mechanics, eliminating the need for complex lens fabrication and polishing processes while achieving comparable or superior spot size reduction
Solution Approach 2:
The patent modifies optical parameters by using sub-wavelength grating periods and varying duty cycles to control the phase and amplitude of transmitted light. By adjusting grating geometric parameters (period, width, depth), the system achieves different focusing characteristics without changing physical lens curvature or material properties, thereby simplifying manufacturing
2Area of moving object
If conventional convex lenses are used to minimize beam width, then spot size is reduced, but compatibility with planar integrated circuits is lost
Solution Approach 1:
The patent replaces three-dimensional mechanical lenses with planar diffraction grating structures that can be integrated into flat optical circuits. The grating-based approach maintains planarity while achieving beam focusing, enabling compatibility with planar integrated circuit architectures that cannot accommodate bulky conventional lenses
Solution Approach 2:
The patent transitions from three-dimensional lens geometry to two-dimensional planar grating patterns. By encoding optical functionality in the lateral dimensions of planar gratings rather than through vertical curvature, the system achieves lens-like focusing in a planar format that integrates seamlessly with flat electronic and optical circuits
3Speed
If focusing grating couplers are used to produce focused beam, then light can be projected into free-space and focused, but the device cannot couple light from free space to free space
Solution Approach 1:
The patent designs diffraction grating structures that can operate in multiple coupling configurations. The same grating-based optical element can function as a waveguide-to-free-space coupler, a free-space-to-waveguide coupler, or a free-space-to-free-space beam shaper, providing universal functionality across different coupling scenarios without requiring separate specialized components
Solution Approach 2:
The patent employs reciprocal optical design where the grating structure operates in reverse for different coupling directions. By using the same periodic structure to both launch beams from waveguides and receive/collimate beams from free space, the system achieves bidirectional coupling capability, effectively enabling free-space-to-free-space coupling through inverted operation modes
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
These devices effectively reduce beam width by applying specific phase changes to light, enabling the creation of optical elements with desired optical properties, such as focusing or diverging light, while being cost-effective and compatible with planar integrated circuits.
Implementation Method 1
Optical devices including one or more high contrast, sub-wavelength diffraction gratings configured to operate as optical elements
Data Source
AI summary
Embodiments of the present invention relate to planar optical devices composed of one or more sub-wavelength diffraction grating layers. In one embodiment, an optical device includes a first substantially planar reflective structure (104,1904), a second substantially planar reflective structure (106,1906), and a substantially planar sub-wavelength grating layer (102,1902) disposed between the first reflective structure and the second reflective structure. The grating layer is configured with lines (208-211,214-217) having line widths, line thicknesses, and line period spacing selected to control phase changes in different portions of a beam of light transmitted through the optical device.