2D Photonic Crystal Laser with Transparent Conductive Cladding
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Solution Overview
Problem
Conventional laser fabrication techniques are complex and inefficient, with issues such as slow deposition rates, ultra-clean surface requirements, ion damage to semiconductor materials, and difficulty in controlling impurity profiles, necessitating a simpler approach for developing two-dimensional photonic crystal surface-emitting lasers.
Innovation Solution
A two-dimensional photonic crystal surface-emitting laser with a transparent conductive cladding layer, comprising a substrate, graded-refractive layers, optical confinement layers, a photonic crystal region, and a transparent conductive layer, which facilitates uniform current spreading and light confinement to produce a laser beam, while preventing mode competition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional laser fabrication techniques are used, then laser devices can be produced, but the fabrication process becomes complex and inefficient with slow deposition rates
Solution Approach 1:
The laser device is segmented into distinct functional layers including N-type graded-refractive layer, N-type cladding layer, N-type optical confinement layer, emission layer, P-type optical confinement layer, photonic crystal region with P-type injection layer, current confinement structure, and transparent conductive layer. This segmentation allows each layer to be optimized independently for its specific function, simplifying the overall fabrication process while maintaining high productivity
Solution Approach 2:
Different regions of the device have locally optimized properties: the photonic crystal region provides localized optical confinement with periodic hole structures, the current confinement structure restricts current flow to specific areas, and the transparent conductive layer provides selective electrical conductivity. This local quality approach enables efficient fabrication by addressing specific functional requirements in specific regions rather than requiring complex global processing
2Manufacturing precision
If conventional fabrication methods are used, then laser structures can be formed, but ultra-clean surface with ultra-low roughness is required
Solution Approach 1:
The invention uses graded-refractive layers with gradually changing composition ratios (e.g., AlGaInAs layers with varying Al content from 0.3 to 0.0) to achieve smooth transitions between regions. This parameter change approach creates ultra-low roughness surfaces without requiring extremely complex fabrication processes, as the gradual composition changes naturally produce smooth interfaces during epitaxial growth
3Use of energy by moving object
If conventional laser structures are used, then light emission can be achieved, but current crowding and heat generation occur
Solution Approach 1:
The transparent conductive layer acts as an intermediary between the current confinement structure and the photonic crystal region, distributing current uniformly across the emission area. This intermediary layer prevents current crowding at specific points, reducing localized heat generation and improving quantum efficiency by ensuring uniform carrier injection across the active region
Solution Approach 2:
The invention replaces traditional metal contact structures with a transparent conductive oxide layer that provides electrical conduction without the mechanical stress and current crowding associated with metal electrodes. This substitution eliminates the harmful thermal effects of conventional electrical contacts while maintaining efficient current injection
4Illumination intensity
If photonic crystal regions are used for light confinement, then laser beam emission is improved, but mode competition occurs
Solution Approach 1:
The photonic crystal region employs an asymmetric periodic hole structure where holes are arranged in a non-uniform pattern within the P-type injection layer. This asymmetric design creates a unique mode profile that suppresses competing modes while maintaining the desired fundamental mode, thereby improving laser beam quality and mode stability simultaneously
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 configuration allows for efficient light emission with reduced current crowding and heat generation, enabling operation at normal temperatures with improved quantum efficiency and centralized laser beam emission, overcoming the limitations of conventional laser fabrication methods.
Implementation Method 1
the photonic crystal region is comprised of a P-type injection layer and a plurality of periodic holes formed in the P-type injection layer
Implementation Method 2
the light produced by the emission layer can resonate in the photonic crystal region to produce a laser beam
Implementation Method 3
with configuration of the current confinement structure and the transparent conductive layer, current can spread uniformly
Implementation Method 4
The N-type optical confinement layer is then disposed on the N-type cladding layer. Disposed on the N-type optical confinement layer is the emission layer. The P-type optical confinement layer is then disposed on the emission layer
Data Source
AI summary
A two-dimensional photonic crystal laser with transparent conductive cladding layer is provided. The two-dimensional photonic crystal region through the etching process is composed by multiple periodic air-holes with proper duty cycle. Then, the transparent conductive oxide layer is directly deposited on the top of the entire two-dimensional photonic crystal structure to cover the entire two-dimensional photonic crystal structure in order to form a current spreading layer. The configuration and the process condition of transparent conductive oxide layer are optimized to provide uniform current spreading path and the transparency. In addition to simplifying the whole fabrication process, the optical confinement is improved and the maximum gain to optical feedback is obtained. Overall, low threshold, small divergence angle and high quality laser output is achieved to satisfy the requirements for next-generation light sources.