Surface Emitting Laser Spacer Layer Segmentation for Heat Dissipation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional surface emitting lasers face challenges in achieving single transverse mode oscillation and sufficient heat dissipation capacity, particularly with thick AlAs films being difficult to grow and resulting in rough crystal surfaces, which limits their performance in red band emission applications.
Innovation Solution
A surface emitting laser design incorporating a spacer layer with alternately stacked heat conductive and lower thermal conductivity semiconductor sublayers, forming a long cavity structure that enhances heat dissipation and allows for single transverse mode oscillation, using materials like AlAs and AlGaAs to manage thermal conductivity and optical absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick spacer layer is used to achieve single transverse mode oscillation, then the diffraction loss of higher-order modes increases, but the crystal surface becomes rough and the layer is difficult to grow
Solution Approach 1:
The thick spacer layer is segmented into multiple thin sublayers with alternating materials (AlAs and AlGaAs). Each sublayer has a thickness of about 0.1-0.5 μm, which is much thinner than the conventional single thick layer. This segmentation allows the total optical thickness to be sufficient for single transverse mode oscillation while keeping individual layer thicknesses within the manufacturable range that avoids surface roughness
Solution Approach 2:
The spacer layer is constructed as a composite structure with alternating AlAs and AlGaAs sublayers. This composite material approach allows optimization of both thermal conductivity (through AlAs layers) and optical absorption characteristics (through AlGaAs layers), while maintaining manufacturability by keeping individual sublayer thicknesses small enough to avoid surface roughness issues
2Reliability
If the cavity length is increased to achieve single transverse mode oscillation, then the diffraction loss of higher-order modes increases, but the heat dissipation capacity decreases
Solution Approach 1:
The long cavity spacer layer is segmented into multiple thin alternating sublayers. This segmentation enables the cavity to achieve sufficient optical thickness for single transverse mode oscillation while incorporating materials with different thermal conductivities at regular intervals, improving heat dissipation along the cavity length
Solution Approach 2:
The alternating AlAs and AlGaAs sublayers create a composite structure where AlAs layers provide high thermal conductivity for heat dissipation, while AlGaAs layers provide appropriate optical absorption characteristics. This composite approach simultaneously addresses both the optical requirement for single transverse mode oscillation and the thermal requirement for effective heat dissipation
3Temperature
If AlAs film is grown thicker to improve heat dissipation, then the thermal conductivity increases, but the crystal surface becomes rough
Solution Approach 1:
The thick AlAs film is segmented into multiple thin AlAs sublayers separated by AlGaAs sublayers. Each AlAs sublayer has a thickness of about 0.1-0.5 μm, which is thin enough to maintain smooth crystal surface while the cumulative thickness and alternating structure provide sufficient heat dissipation capacity
Solution Approach 2:
The alternating AlAs and AlGaAs sublayers form a composite structure where heat dissipation is achieved through the high thermal conductivity AlAs layers, while the overall structure remains manufacturable because individual AlAs layer thicknesses are kept small. The AlGaAs layers act as spacers that prevent surface roughness accumulation
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 design achieves higher laser output and improved heat dissipation capacity, enabling single transverse mode oscillation and reducing surface roughness, thus overcoming the limitations of conventional surface emitting lasers.
Implementation Method 1
A spacer layer includes alternately stacked heat conductive first semiconductor sublayers and second semiconductor sublayers having lower thermal conductivity than the first semiconductor sublayers
Implementation Method 2
the divergence angle for a beam of a higher-order mode is larger than that for a fundamental mode. Thus, in a surface emitting laser having a long cavity structure, a beam of a higher-order mode tends to have a large diffraction loss while propagating between the DBRs
Data Source
AI summary
A surface emitting laser that oscillates at a wavelength λ includes an upper reflector, a lower reflector, an active layer, and a spacer layer. The spacer layer is a laminated structure that includes a first semiconductor sublayer having a composition of AlxGa1-xAs (1≧x>0) and a second semiconductor sublayer having a composition of AlyGa1-yAs (1>y>0 and x>y).