Vertically Emitting Laser Diode With Bottom Reflective Surface
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Solution Overview
Problem
Existing semiconductor lasers, particularly edge emitting diodes, require individual cutting for testing, increasing costs, while surface emitting VCSELs emit low power and are limited by fiber optic absorption and dispersion issues, and attempts to integrate internal mirrors using ion-beam milling are inaccurate and not commercially viable.
Innovation Solution
A semiconductor laser diode with a gain layer and diffraction grating feedback layer, featuring a reflective surface along a (111)A crystalline plane, redirects the laser beam to emit from the surface, allowing for surface emission with improved accuracy and power through a 45-degree etched reflective surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If VCSELs are used for surface emission, then wafer-level testing is enabled reducing cost, but emission power is low and limited to short optical links
Solution Approach 1:
The patent inverts the conventional VCSEL architecture by placing the reflective surface at the bottom of the die rather than using top-surface emission. The laser beam is generated in the gain layer and reflected upward by the bottom reflective surface, enabling surface emission with high power capability while maintaining wafer-level testing compatibility
2Power
If edge emitting diodes are used, then high power emission is achieved, but individual die cutting is required increasing testing cost
Solution Approach 1:
The patent inverts the emission direction by using a bottom reflective surface to redirect the laser beam upward through the top surface of the die. This allows edge-emitting diode structures to be tested at the wafer level before cutting, combining the high power capability of edge emitters with the manufacturing efficiency of surface-emitting devices
3Ease of manufacture
If ion-beam milling is used to create internal mirrors, then beam reflection is achieved, but manufacturing accuracy is poor producing rough surfaces
Solution Approach 1:
The patent changes the manufacturing approach from ion-beam milling to epitaxial growth with selective removal. The reflective surface is created by growing a sacrificial layer during epitaxial growth, then selectively removing it to expose a highly reflective crystalline plane. This parameter change in the manufacturing process achieves atomic-level smoothness compared to the rough surfaces from ion-milling
4Ease of manufacture
If VCSELs emit at 850 nm, then surface emission is achieved, but fiber optic absorption and dispersion are high
Solution Approach 1:
The patent changes the operational wavelength parameter from 850 nm to 1310 nm or 1550 nm by adjusting the gain layer composition and thickness. This parameter change enables the device to operate at wavelengths with lower fiber optic absorption and dispersion while maintaining surface emission capability through the bottom-reflective-surface architecture
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
Enables cost-effective testing and increased power emission from the surface, overcoming limitations of edge emitting diodes and improving the accuracy of mirror integration, suitable for longer optical links with reduced fiber optic absorption and dispersion.
Implementation Method 1
The reflective surface reflects a laser beam generated within the semiconductive die so that the beam is emitted from a surface of the die
Implementation Method 2
A semiconductor laser diode that includes a gain layer and a diffraction grating feedback layer within a semiconductive die
Data Source
AI summary
A semiconductor laser that has a reflective surface. The reflective surface redirects the light of an edge emitting laser diode to emit from the top or bottom surface of the diode. The laser may include a gain layer and a feedback layer located within a semiconductive die. The gain and feedback layers generate a laser beam that travels parallel to the surface of the die. The reflective surface reflects the laser beam 90 degrees so that the beam emits the die from the top or bottom surface. The reflective surface can be formed by etching a vicinally oriented III-V semiconductive die so that the reflective surface extends along a (111)A crystalline plane of the die.