Photonic-Crystal Surface Laser Lattice for Flat Embedding Layers
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Solution Overview
Problem
The surface of an embedding layer for a two-dimensional photonic crystal in photonic-crystal surface-emitting lasers becomes rough due to shape changes of air holes during mass transport, leading to quality deterioration of the active layer and reduced laser light extraction efficiency.
Innovation Solution
A photonic-crystal surface-emitting laser with a multiple lattice structure where air holes of different sizes are periodically arranged, ensuring improved flatness and crystallinity of the embedding layer and active layer, allowing for high light extraction efficiency and low threshold current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a laser element is mounted on a heat dissipation substrate with large area thermal conduction paths, then heat dissipation capability is improved, but the laser element becomes susceptible to external stress and deformation
Solution Approach 1:
The heat dissipation path is segmented into multiple independent thin-film layers (first heat dissipation layer, second heat dissipation layer, third heat dissipation layer) rather than using a single large-area thermal conduction path. Each layer has a width smaller than the laser element, creating multiple discrete thermal conduction channels that reduce stress transmission while maintaining heat dissipation capability.
Solution Approach 2:
The patent uses composite material structures with different properties: the first heat dissipation layer has higher stress resistance, the second has higher thermal conductivity, and the third has lower stress. This composite approach allows simultaneous optimization of heat dissipation and stress resistance that cannot be achieved with a single material.
2Stability of the object's composition
If the laser element is fixed rigidly to the substrate, then positional stability is improved, but stress concentration and deformation occur
Solution Approach 1:
Different regions of the heat dissipation structure have different properties optimized for their specific functions. The first heat dissipation layer positioned directly under the laser element has higher stress resistance to protect the element, while the second layer has higher thermal conductivity for heat dissipation, and the third layer has lower stress for flexibility. This local differentiation resolves the contradiction between rigid fixing and stress reduction.
3Strength
If thin-film heat dissipation layers are used, then stress resistance is improved, but thermal conductivity decreases
Solution Approach 1:
The second heat dissipation layer is designed to perform multiple functions simultaneously: it provides thermal conduction for heat dissipation while also contributing to the overall stress resistance of the structure. By optimizing its thickness and material properties, it serves dual purposes rather than requiring separate layers for each function, thus improving thermal conductivity without compromising stress resistance.
4Reliability
If the first heat dissipation layer has higher stress resistance, then protection against deformation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the thickness parameter of the first heat dissipation layer (50-200 nm) to achieve the desired stress resistance while maintaining compatibility with existing thin-film fabrication processes. By carefully controlling this parameter, the layer provides adequate protection against deformation without requiring complex manufacturing procedures, thus resolving the contradiction between reliability and ease of manufacture.
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 achieves high flatness and crystallinity of the active layer, resulting in improved light extraction efficiency and low threshold current density, enabling efficient laser operation.
Implementation Method 1
the first heat dissipation layer has higher stress resistance than the second heat dissipation layer
Implementation Method 2
the second heat dissipation layer has higher thermal conductivity than the third heat dissipation layer
Implementation Method 3
surface-emitting laser element that emits laser beams in a surface direction
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3
AI summary
A surface-emitting laser element includes: a first guide layer including a photonic crystal layer that is formed on a c plane of a group-3 nitride semiconductor and includes air holes arranged with two-dimensional periodicity in a plane parallel to the photonic crystal layer, and an embedding layer that is formed on the photonic crystal layer and closes the air holes; an active layer formed on the first guide layer; and a second guide layer formed on the active layer, wherein an air hole set including at least a main air hole and a sub-air hole smaller in size than the main air hole is arranged at each square lattice point in the plane parallel to the photonic crystal layer, and wherein the main air hole has a regular-hexagonal prism shape, a long-hexagonal prism shape, or an elliptic cylindrical shape with a major axis parallel to a <11-20> axis.