Superluminescent Diode Waveguide for High-Power Display Illumination
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Solution Overview
Problem
Current semiconductor light sources, such as LEDs and LDs, face challenges in achieving high optical output power and efficient collimation of light beams, leading to limitations in display and illumination applications, with LEDs offering low power and LDs experiencing coherence-related issues like speckle formation and polarization.
Innovation Solution
A heterostructure-based light source with a waveguide and optically active zone capable of emitting light at multiple radiative transitions in the visible spectrum, incorporating features like antireflective coatings and tapered waveguides to prevent light reflections, and utilizing nitride compounds for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the emitting area is enlarged to increase optical output power, then the power output is improved, but the beam quality deteriorates and collimation becomes difficult
Solution Approach 1:
The device is segmented into multiple independent laser diodes arranged in a specific geometric configuration (e.g., tetrahedral, octahedral, or icosahedral arrangements). Each laser diode acts as an independent light source with its own beam characteristics, and their combined output achieves high total power while maintaining good beam quality through proper spatial arrangement and optical coupling.
2Power
If laser diodes are used to achieve high power and good coupling efficiency, then energy conversion and spatial coherence are improved, but speckle formation and polarization issues occur
Solution Approach 1:
Multiple laser diodes are used instead of a single laser source. The speckle patterns generated by each individual laser diode are spatially incoherent with each other due to their different positions and emission characteristics. When these multiple speckle patterns are superimposed, they average out to reduce overall speckle visibility and distortion in the displayed image.
Solution Approach 2:
Each laser diode in the array is positioned and oriented to provide locally optimized beam characteristics. The spatial distribution and angular orientation of individual diodes are carefully designed to ensure that their combined output achieves uniform illumination and minimal speckle while maintaining high coupling efficiency to the optical waveguide.
3Adaptability or versatility
If multiple laser sources are combined to complete the color gamut, then color representation is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses a small set of laser diodes with specific wavelengths (blue, cyan, green, yellow-green, red) that can collectively cover the entire visible spectrum. By carefully selecting the wavelength combinations and spatial arrangements, a single device configuration can achieve full color gamut coverage for display applications, eliminating the need for multiple separate light sources or complex color conversion systems.
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 solution enables a high-power, efficient light source with improved beam quality and reduced coherence issues, suitable for display and illumination systems, potentially surpassing the limitations of existing technologies.
Implementation Method 1
at least two different radiative transitions being excitable in the optically active zone, transition energies of said at least two different radiative transitions corresponding to wavelengths in the visible part of the optical spectrum
Implementation Method 2
a narrow waveguide confines the electromagnetic radiation resulting in good in-fiber coupling of the light, i.e. high spatial coherence
Implementation Method 3
means for preventing reflections of light from the waveguide by at least one of said first and second end back into the waveguide
Data Source
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AI summary
In accordance with the invention, a light source for display and/or illumination is provided, the light source comprising a heterostructure including semiconductor layers, the heterostructure forming a waveguide between a first end and a second end, the heterostructure comprising a plurality of layers and comprising an optically active zone formed by the plurality of layers, the optically active zone capable of emitting light guided by said waveguide, at least two different radiative transitions being excitable in the optically active an electrical current between a p-side electrode and an n-side electrode, transition energies of said at least two different radiative transitions corresponding to wavelengths in the visible part of the optical spectrum, the light source further comprising means for preventing reflections of light from the waveguide by at least one of said first and second end back into the waveguide, thereby causing the light source to comprise a superluminescent light emitting diode.