μLED Metasurface Beam Shaping for Waveguide Coupling
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Solution Overview
Problem
Conventional micro light emitting diodes (μLEDs) in near-eye displays suffer from inefficient light coupling due to Gaussian transverse beam profiles, resulting in significant light loss and reduced brightness, which is crucial for improving display quality in augmented and virtual reality systems.
Innovation Solution
Applying a metasurface of nanostructures on μLEDs to manipulate beam profiles, directionality, and polarization using adjoint simulation and shape optimization techniques to enhance coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional μLEDs are used with Gaussian transverse beam profiles, then the light emission is simple and easy to manufacture, but the coupling efficiency to waveguide is poor resulting in significant light loss
Solution Approach 1:
The patent applies parameter changes by transforming the beam profile from Gaussian to asymmetric shape through metasurface nanostructures. The metasurface modifies the spatial distribution of light intensity and directionality parameters, converting the symmetric Gaussian profile into an asymmetric profile that matches the waveguide coupling requirements, thereby reducing light loss while maintaining manufacturability
Solution Approach 2:
The metasurface acts as an intermediary component between the μLED and the waveguide. It mediates the light transformation process by receiving the Gaussian beam from the μLED and converting it into an asymmetric profile suitable for waveguide coupling, thus resolving the mismatch between the light source characteristics and the waveguide requirements without requiring direct modification of the μLED or waveguide
2Device complexity
If conventional μLEDs with Gaussian beam profiles are used, then the device structure is simple, but the brightness and overall system efficiency are reduced
Solution Approach 1:
The metasurface changes the beam profile parameters from Gaussian to asymmetric, optimizing the spatial distribution of light intensity. This parameter transformation concentrates the light energy in directions that couple more efficiently to the waveguide, thereby increasing the effective brightness and system efficiency while adding minimal structural complexity
Solution Approach 2:
The patent introduces asymmetry into the beam profile through metasurface nanostructures. The asymmetric beam profile is specifically designed to match the asymmetric coupling requirements of the waveguide, improving light coupling efficiency and brightness. The asymmetry is achieved through carefully designed nanostructure geometries that redistribute light intensity asymmetrically
3Shape
If beam shaping is performed by covering a portion of radiated light, then the beam profile can be modified, but approximately 40% of light is lost
Solution Approach 1:
Instead of blocking light to shape the beam, the metasurface changes the parameters of the light distribution by transforming the Gaussian profile into an asymmetric profile. This parameter transformation achieves the desired beam shaping while preserving the majority of light energy, avoiding the 40% loss associated with blocking portions of the radiated 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 metasurface optimization significantly reduces light loss, increasing brightness and overall system efficiency by shaping the beam towards an asymmetric profile for improved waveguide coupling.
Implementation Method 1
manipulate a beam profile, directionality, and/or polarization of emitted light
Implementation Method 2
manipulate a beam profile, directionality, and/or polarization of emitted light
Implementation Method 3
manipulate a beam profile, directionality, and/or polarization of emitted light to increase coupling efficiency
Data Source
AI summary
A far-field characteristic of light emitted by a micro light emitting diode (μLED) such as a beam shape, a beam orientation, a beam focusing, or a beam polarization is controlled by a metasurface of nanostructures formed on the μLED. The metasurface is characterized or defined by a far-field objective function for the emitted light, selection of a nanostructure shape, and application of one or more fabrication constraints to shape parameters for the selected nanostructure shape. A number and a location of the nanostructures is determined employing an adjoint simulation technique, and the shape parameters for the nanostructure are tuned employing a shape optimization technique.