Photonic-Crystal Surface Laser Electrode Layout for Lower Light Scattering
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Solution Overview
Problem
Photonic-crystal surface emitting lasers experience reduced optical output due to light scattering and scattering at the electrode interface, which limits their efficiency.
Innovation Solution
The laser design incorporates a photonic crystal layer with alternating refractive indices and an insulating film with openings, reducing the contact area between the second electrode and the semiconductor layer, thereby minimizing light scattering and enhancing reflectivity through controlled phase adjustment of light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second electrode is provided directly on the second semiconductor layer, then electrical connection is achieved, but light scattering increases and reflectivity decreases
Solution Approach 1:
An insulating film is introduced as an intermediary layer between the second electrode and the second semiconductor layer. This film has openings that allow electrical connection while the film material itself reduces light scattering at the electrode-semiconductor interface, thereby maintaining electrical connectivity while minimizing optical loss
Solution Approach 2:
The insulating film is provided with openings at specific locations rather than being continuous. This creates local variations in structure: areas with openings allow electrical connection, while areas covered by the insulating film reduce light scattering. This localized differentiation resolves the contradiction between needing electrical connection and minimizing light scattering
2Reliability
If the contact area between the second electrode and the second semiconductor layer is increased, then electrical connection is improved, but the lower surface of the second electrode becomes roughened and reflectivity decreases
Solution Approach 1:
The insulating film serves as a mediator that separates the electrode from direct contact with the semiconductor layer. The openings in the film provide sufficient electrical connection area while the film coating on the electrode's lower surface prevents roughening, thereby maintaining both electrical connectivity and optical reflectivity
Solution Approach 2:
The physical state and surface properties of the electrode-semiconductor interface are changed by introducing the insulating film. The film alters the contact parameters, providing electrical connection through openings while preventing the surface roughening that would otherwise occur with direct contact, thus preserving reflectivity
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 increases optical output by reducing scattering and improving reflectivity, allowing for higher optical output and uniform current injection.
Implementation Method 1
a photonic crystal layer provided between the first semiconductor layer and the second semiconductor layer. The photonic crystal layer has a first region and a plurality of second regions each having a refractive index different from a refractive index of the first region
Implementation Method 2
the output is reduced due to the scattering of light. Since the insulating film is provided between the second electrode and the second semiconductor layer, a contact area between the second electrode and the second semiconductor layer is reduced. A lower surface of the second electrode is less likely to be roughened, and the reflectivity is increased
Implementation Method 3
The phase of light is adjusted by a thickness of the insulating film
Implementation Method 4
Light generated in an active layer is reflected from the electrode, whereby the light can be extracted
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
A photonic-crystal surface emitting laser (100, 200, 300, 400) includes a first semiconductor layer (12), an active layer (18) stacked over the first semiconductor layer, a second semiconductor layer (22) provided opposite to the first semiconductor layer with respect to the active layer, a photonic crystal layer (14) provided between the first semiconductor layer and the second semiconductor layer, a first electrode (24) electrically connected to the first semiconductor layer, an insulating film (23) provided on a surface of the second semiconductor layer opposite to the active layer, and a second electrode (26) provided at a surface of the insulating film opposite to the second semiconductor layer. The photonic crystal layer has a first region (30) and a plurality of second regions (32, 34) each having a refractive index different from a refractive index of the first region. The insulating film has a plurality of openings (27). The second electrode is electrically connected to the second semiconductor layer at the plurality of openings.