Photonic-crystal surface emitting laser and method of manufacturing the same
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Solution Overview
Problem
Photonic-crystal surface emitting lasers (PCSELs) face challenges in operating in a single mode due to higher order modes being excited, primarily because carrier density is higher near the periphery, making it difficult to achieve oscillation in a fundamental mode.
Innovation Solution
The PCSEL design includes a multi-ring structure in the second semiconductor layer with varying ring widths, where the ring closer to the center has a larger width and those closer to the periphery have a smaller width, coupled with a carrier density distribution that increases near the center and decreases towards the outer periphery, facilitated by a concentric arrangement of a central portion and ring portions, and a second electrode covering these structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carriers are injected into the semiconductor layer near the outer periphery, then carrier density is higher near the periphery, but higher order modes are excited and single mode oscillation becomes difficult
Solution Approach 1:
The patent applies local quality by creating a non-uniform multi-ring structure in the second semiconductor layer where ring portions have different widths at different locations. The ring portions closer to the center have larger widths while those near the periphery have smaller widths, resulting in localized carrier density variations that suppress higher order modes and enable stable fundamental mode oscillation
Solution Approach 2:
The second semiconductor layer is segmented into multiple discrete ring portions arranged in a multi-ring structure. This segmentation allows independent control of carrier injection at different radial positions, creating the desired carrier density distribution profile that favors fundamental mode operation while maintaining overall device functionality
2Reliability
If a multi-ring structure is formed in the second semiconductor layer with varying ring widths, then carrier density distribution is optimized for single mode oscillation, but device structure becomes more complex
Solution Approach 1:
The patent utilizes parameter changes by systematically varying the width parameter of ring portions across different radial positions in the multi-ring structure. This controlled parameter variation creates the necessary carrier density gradient to suppress higher order modes while maintaining a manufacturable structure through standardized geometric progressions
3Power
If the second electrode covers the plurality of ring portions, then light output is increased through reflection, but manufacturing precision requirements increase
Solution Approach 1:
The second electrode serves multiple functions simultaneously: it provides electrical connection to the second semiconductor layer, acts as a reflective surface to enhance light output, and defines the active region through its geometric coverage of the multi-ring structure. This multi-functionality reduces the need for separate components and simplifies the overall device 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
This design suppresses higher order modes and enhances the likelihood of oscillation in a single mode, allowing for higher carrier density at the center and lower density at the periphery, thereby promoting fundamental mode excitation and increasing light output.
Implementation Method 1
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 second electrode reflects light, the output of light can be increased
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
A photonic-crystal surface emitting laser (100, 110) includes a first semiconductor layer (12, 16), an active layer (18) stacked on the first semiconductor layer, a photonic crystal layer (14) stacked on or under the active layer, a second semiconductor layer (22) provided opposite to the first semiconductor layer with respect to the active layer, a first electrode (24) electrically connected to the first semiconductor layer, and a second electrode (26) electrically connected 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 second semiconductor layer has a plurality of ring portions (42). The plurality of ring portions form a multi-ring structure.