Laser Projection Display Using Nonpolar GaN for Wavelength Stability
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Solution Overview
Problem
Conventional display technologies face inefficiencies in projecting large images due to internal polarization-related electric fields in InGaN-based lasers and LEDs, leading to reduced radiative recombination efficiency and wavelength dependence on drive current, which is undesirable for display applications.
Innovation Solution
The use of blue and green laser diodes fabricated on nonpolar or semipolar oriented gallium nitride substrates, which eliminate or mitigate polarization fields, resulting in higher radiative recombination efficiency, reduced peak wavelength shift with drive current, and improved epitaxial growth quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional InGaN-based lasers and LEDs are used, then device structure is simple and manufacturing is easier, but internal polarization-related electric fields reduce radiative recombination efficiency
Solution Approach 1:
The patent changes the crystallographic orientation parameter of the GaN substrate from conventional polar c-plane to nonpolar a-plane or semipolar planes. This parameter change eliminates or mitigates the internal polarization-related electric fields that reduce radiative recombination efficiency in conventional InGaN-based devices.
Solution Approach 2:
The patent employs composite material structures including InGaN quantum wells grown on nonpolar or semipolar GaN substrates. This composite approach combines the beneficial optical properties of InGaN with the reduced polarization effects of nonpolar/semipolar orientations to achieve higher radiative recombination efficiency.
2Manufacturing precision
If conventional polar GaN substrates are used, then epitaxial growth is simpler, but peak wavelength shifts significantly with drive current
Solution Approach 1:
The patent changes the substrate orientation parameter to nonpolar or semipolar planes, which fundamentally alters the electric field distribution and reduces the quantum confined Stark effect. This results in significantly reduced peak wavelength shift with drive current while maintaining manufacturability through established epitaxial growth techniques.
3Loss of energy
If polar oriented GaN materials are used, then manufacturing process is simpler, but optical losses are increased due to polarization effects
Solution Approach 1:
The patent applies parameter change by transitioning from polar to nonpolar or semipolar substrate orientations, which eliminates the polarization-related optical losses inherent in conventional InGaN devices while maintaining compatibility with existing manufacturing processes.
4Speed
If conventional laser diodes are used in projection systems, then system design is simpler, but modulation frequencies are limited
Solution Approach 1:
The patent changes the fundamental material parameter of substrate orientation to nonpolar or semipolar GaN, which reduces internal electric fields and enables higher carrier recombination rates. This parameter change directly enables higher modulation frequencies suitable for advanced display applications while maintaining manageable device complexity.
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 enables the development of highly efficient, polarized, and compact projection systems with minimized optical losses, reduced speckle, and increased modulation frequencies, suitable for pico projectors and other display technologies.
Implementation Method 1
a first light source including a first set of laser diodes: a red laser diode, a green laser diode, and a blue laser diode
Implementation Method 2
blue and green laser diodes fabricated on nonpolar or semipolar oriented gallium nitride substrates, which eliminate or mitigate polarization fields, resulting in higher radiative recombination efficiency
Data Source
AI summary
The present invention is directed to display technologies. More specifically, various embodiments of the present invention provide projection display systems where one or more laser diodes are used as a light source.