VECSEL Arrays with Volume Bragg Grating for Alignment Reduction
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Solution Overview
Problem
Conventional digital light processing (DLP) systems using white light discharge lamps are limited by brightness, energy efficiency, color saturation, and high costs, while semiconductor lasers face challenges such as high cost, lower power output, and speckle issues, making them unsuitable for cost-effective and high-brightness projection display applications.
Innovation Solution
A semiconductor, vertical, extended-cavity, surface-emitting laser array with intra-cavity nonlinear frequency doubling is developed, incorporating a gain chip, nonlinear crystal, and polarization control elements, where a volume Bragg grating combines the functionality of an end reflector and wavelength control, reducing alignment complexity and increasing optical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional white light discharge lamps are used in DLP systems, then high brightness and high lumen output are achieved, but the system suffers from poor energy efficiency, limited color saturation, and high cost
Solution Approach 1:
The patent replaces the conventional white light discharge lamp (thermal/radiative system) with semiconductor lasers (electroluminescent system). The laser diodes convert electrical energy directly to optical energy with minimal thermal loss, achieving over 50% electrical-to-optical conversion efficiency compared to the inefficient thermal radiation process of discharge lamps. This substitution resolves the contradiction by using a fundamentally different energy conversion mechanism that is inherently more efficient.
Solution Approach 2:
The patent changes the spectral parameters from broad-spectrum white light to narrow-band laser wavelengths. By using specific laser wavelengths (red, green, blue) that match the peak sensitivity of the human eye and the transmission characteristics of optical components, the system achieves higher perceived brightness and better color saturation while reducing total power consumption. The spectral purity of lasers eliminates wasted energy in non-useful wavelength ranges.
2Loss of energy
If semiconductor lasers are used to replace white light sources, then energy efficiency and color saturation are improved, but the system suffers from speckle artifacts and insufficient brightness
Solution Approach 1:
The patent divides the laser light source into multiple independent laser diodes arranged in arrays. Each laser diode emits coherent light that creates its own speckle pattern, but the combined speckle patterns from multiple incoherent sources average out to reduce overall speckle visibility. This segmentation of the coherent light source into multiple independent emitters maintains the energy efficiency benefits of lasers while mitigating the speckle artifact problem.
Solution Approach 2:
The patent uses multiple laser diodes emitting from different spatial positions and angles to illuminate the spatial light modulator. By distributing the light sources across multiple dimensions (spatial distribution of laser arrays), the system creates overlapping speckle patterns that when combined reduce the visibility of individual speckle artifacts, while still maintaining the high brightness and energy efficiency of laser sources.
3Manufacturing precision
If multiple discrete optical components are used in semiconductor laser systems, then wavelength control and beam quality are maintained, but manufacturing cost and alignment complexity increase
Solution Approach 1:
The patent integrates multiple optical functions (wavelength selection, beam shaping, polarization control) directly into the laser diode chip structure itself. By merging these functions into the semiconductor device fabrication process rather than using separate discrete optical components, the system maintains precise wavelength control and beam quality while dramatically reducing alignment complexity and manufacturing cost. The laser diode array structure inherently provides the necessary optical control without requiring additional alignment steps.
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 provides a cost-effective, high-brightness light source with reduced speckle, capable of generating red, green, and blue colors efficiently, overcoming the limitations of traditional DLP systems and semiconductor lasers by enhancing power output and manufacturability.
Implementation Method 1
intra-cavity nonlinear frequency doubling
Data Source
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AI summary
Arrays of vertical extended cavity surface emitting lasers (VECSELs) are disclosed. The functionality of two or more conventional optical components are combined into an optical unit to reduce the number of components that must be aligned during packaging.