Surface-Emitting Laser Array with Selective Oxidation and AlGaInP Layers
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Solution Overview
Problem
Typical surface-emitting lasers face challenges in achieving both lower threshold values and higher output power, which are essential for applications such as writing systems and optical disc devices.
Innovation Solution
The surface-emitting laser array is designed with a specific configuration that includes a selectively-oxidized layer positioned at a node of the standing-wave distribution of the electric field, using AlGaInP layers to reduce heat generation and increase the confinement of electrons to the active layer, thereby achieving a lower threshold value and higher output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a typical surface-emitting laser configuration is used, then the device structure is simple, but the threshold value is high and output power is low
Solution Approach 1:
The laser device is segmented into multiple functional layers including a selectively-oxidized layer, AlGaInP layers, and active layer. The selectively-oxidized layer is divided into first and second regions with different oxidation degrees, creating distinct functional zones that collectively improve output power while maintaining manageable structural complexity
Solution Approach 2:
The patent employs composite material structure combining AlGaInP layers with the selectively-oxidized layer. This composite structure leverages the complementary properties of each material: the AlGaInP provides electron confinement and reduces heat generation, while the selectively-oxidized layer provides current injection efficiency, together achieving high output power
2Productivity
If the selectively-oxidized layer is positioned closer to the active layer, then current injection efficiency is improved, but heat generation increases
Solution Approach 1:
The selectively-oxidized layer exhibits local quality variation with a first region having a higher oxidation degree near the active layer for current confinement, and a second region with lower oxidation degree for heat dissipation. This spatial variation in oxidation quality allows simultaneous achievement of high current injection efficiency and reduced heat generation
Solution Approach 2:
The AlGaInP layer serves as an intermediary between the selectively-oxidized layer and the active layer. It mediates the trade-off by providing electron confinement to maintain current injection efficiency while its material properties help manage heat generation, allowing the selectively-oxidized layer to be positioned close to the active layer without excessive heat accumulation
3Ease of manufacture
If AlGaAs layer is used in contact with selectively-oxidized layer, then manufacturing is easier, but heat generation is higher and electron confinement is weaker
Solution Approach 1:
The patent changes the material parameter from conventional AlGaAs to AlGaInP, which has superior properties for this application. The AlGaInP layer provides better electron confinement and lower heat generation while maintaining compatibility with the selectively-oxidized layer, achieving both performance improvement and manufacturability
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 configuration results in a surface-emitting laser array that effectively reduces the threshold value and increases output power, enhancing the reliability and performance of the laser for various applications.
Implementation Method 1
a current constriction layer that is formed by selectively oxidizing a selectively-oxidized layer
Implementation Method 2
employing a specific configuration including a selectively-oxidized layer positioned at a node of the standing-wave distribution of the electric field, using AlGaInP layers to reduce heat generation
Implementation Method 3
increase the confinement of electrons to the active layer, thereby achieving a lower threshold value and higher output power
Data Source
Figure 1A~1B
Figure 2~3
Figure 4A~4B
AI summary
A vertical cavity surface-emitting laser includes on a inclined substrate (101) the following layers. A buffer layer (102), a first lower DBR (103), a MQW active layer (105) between a lower and an upper AlGaInP spacer layer, this layer sequence representing an one wavelength resonator. On top of these layers there is provided an upper DBR comprising alternating low and high refractive index AlGaAs layers (107a) and (107b) with different compositions. Furthermore, the upper DBR comprises a current aperture layer (108) made by oxidisation of an AlGaAs layer at a node of the standing wave of the electric field. The position of the current aperture layer (108) is adjusted by a further AlGaInP layer (107c) being part of the upper DBR (107). An AlGaAs layer (115) may serve as anti-oxidisation layer on top of the current aperture layer (108).