Polarized Micro-LED Waveguide Coupling Efficiency
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Solution Overview
Problem
Micro-LEDs used in waveguide-based display systems face inefficiencies in light emission and coupling due to unpolarized light emission, leading to reduced quantum efficiency and coupling efficiency into optical waveguides.
Innovation Solution
Fabricating micro-LEDs on III-nitride layers grown on semi-polar planes, such as the (2021) plane, which emit highly polarized light, improving quantum efficiency and coupling efficiency by using a substrate with a hexagonal lattice and a waveguide coupler like a lens or grating to enhance polarization-dependent coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If micro-LEDs are used as light sources in waveguide-based display systems, then the size and packing density are improved, but the light coupling efficiency into the waveguide deteriorates due to unpolarized light emission
Solution Approach 1:
The patent changes the crystal orientation parameter of the micro-LED from conventional c-plane to semi-polar planes (such as (2021), (1010), or (1120) planes). This parameter change in the substrate orientation fundamentally alters the light emission characteristics, producing highly polarized light that matches the waveguide's acceptance criteria, thereby resolving the coupling efficiency problem while maintaining the small size advantage of micro-LEDs
2Ease of manufacture
If conventional c-plane micro-LEDs are used, then the manufacturing process is simpler, but the quantum efficiency and light emission efficiency are reduced
Solution Approach 1:
The patent modifies the substrate orientation parameter from c-plane to semi-polar planes during the epitaxial growth process. While this requires adjustments to the manufacturing process, it dramatically improves quantum efficiency and light emission efficiency. The semi-polar orientation reduces non-radiative recombination and enhances carrier injection efficiency, leading to superior optical performance that outweighs the increased fabrication complexity
3Ease of manufacture
If unpolarized light is emitted by micro-LEDs, then the light source is easier to manufacture, but the coupling efficiency into polarization-dependent waveguides deteriorates
Solution Approach 1:
The patent changes the emission polarization state by modifying the crystal orientation parameter of the micro-LED substrate to semi-polar planes. This intrinsic parameter change causes the micro-LED to emit highly polarized light naturally, eliminating the need for external polarization filters or complex optical elements. The polarized light emission directly matches the waveguide's polarization-dependent coupling requirements, significantly improving coupling efficiency while maintaining manufacturing feasibility
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 approach results in a significant increase in light emission efficiency and coupling efficiency, enabling more effective conversion of electrical energy to display light and improved delivery to the user's eyes in waveguide-based display systems.
Implementation Method 1
Light emitting diodes (LEDs) convert electrical energy into optical energy
Implementation Method 2
a micro-LED device is fabricated on III-nitride layers that are epitaxially grown on a semi-polar plane (e.g., (2021) plane), where the micro-LED device may have a high peak quantum efficiency and a low peak efficiency operating current, and may also emit highly polarized light
Implementation Method 3
The display light for the computer-generated images may be generated using micro-LEDs and may be coupled into the waveguides, which may then guide the display light and deliver the display light to user's eyes
Implementation Method 4
an optical waveguide, a micro light emitting diode configured to emit at least partially polarized light, and a waveguide coupler configured to couple the at least partially polarized light emitted from the micro light emitting diode into the optical waveguide
Data Source
AI summary
An optical system includes an optical waveguide, a micro light emitting diode (micro-LED) configured to emit at least partially polarized light, and a waveguide coupler configured to couple the at least partially polarized light from the micro-LED into the optical waveguide with a coupling efficiency higher than a coupling efficiency of the waveguide coupler for unpolarized light. The micro-LED includes a substrate including a hexagonal lattice and having a first surface parallel to a semi-polar plane of the hexagonal lattice, and a plurality of layers grown on the first surface. The plurality of layers includes an active layer that includes a III-nitride material and has a top surface parallel to the semi-polar plane and the first surface of the substrate, such that the light emitted by the micro-LED is at least partially polarized and can be more efficiently coupled into the optical waveguide.