VCSEL with DBR Discontinuity for Bandwidth and Mode Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional surface emitting lasers, such as VCSELs, face limitations in achieving high-power output, unstable single-mode oscillation, and high noise levels due to the similarity in resonance wavelengths between the main and external resonators, which also leads to poor reliability at high current densities.
Innovation Solution
A surface emitting laser design incorporating a Vertical-Cavity Surface Emitting Laser (VCSEL) structure with a top Distributed Bragg Reflector (DBR) and an optically discontinuous portion in the DBR, arranged apart from the oxide aperture in the transverse direction, forming multiple external resonators with different resonance wavelengths and coupling coefficients to enhance modulation bandwidth and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the main resonator and external resonator have the same cross-sectional structure and resonator length, then high-speed modulation is supported through light feedback, but single-mode oscillation becomes unstable due to similar resonance wavelengths
Solution Approach 1:
The patent applies local quality by giving the main resonator and external resonator different cross-sectional structures while maintaining the same VCSEL active layer. The external resonator has a larger cross-sectional area than the main resonator, creating different resonance wavelengths and mode profiles. This local structural differentiation allows the external resonator to provide feedback for high-speed modulation without causing single-mode oscillation instability, as the mode fields are spatially distinguished.
Solution Approach 2:
The patent segments the resonator system into two distinct functional parts: a main resonator with smaller cross-section for stable single-mode oscillation, and an external resonator with larger cross-section for providing feedback that extends modulation bandwidth. The segmentation is achieved through selective oxidation patterns that define different aperture sizes and shapes, allowing each resonator to perform its specific function independently while working together as a unified system.
2Stability of the object's composition
If the oxide aperture size is reduced to support stable single-mode oscillation, then single-mode operation is maintained, but reliability deteriorates at high current densities
Solution Approach 1:
The patent segments the current confinement function between two structures: the oxide aperture for optical mode confinement and the p-type electrode for current injection. This segmentation allows the oxide aperture to be optimized for single-mode oscillation with appropriate size, while the p-type electrode provides robust current confinement and heat dissipation, ensuring reliability at high current densities. The p-type electrode extends beyond the oxide aperture, providing additional current confinement capability.
Solution Approach 2:
The patent introduces a p-type electrode as an intermediary structure between the oxide aperture and the external circuit. This p-type electrode serves as a mediator that provides both electrical current confinement and thermal management functions. It allows the oxide aperture to maintain its optimal size for single-mode operation while the p-type electrode handles the high current density requirements, thus resolving the contradiction between mode stability and device reliability.
3Device complexity
If a conventional VCSEL structure is used without optically discontinuous portions, then the structure is simple, but modulation bandwidth is limited
Solution Approach 1:
The patent introduces optically discontinuous portions (reflective layers with different optical properties) as intermediary elements within the resonator structure. These discontinuous portions create the external resonator cavity and enable light feedback without requiring complete structural redesign. The discontinuous portions are strategically placed to provide the necessary optical feedback while maintaining overall structural simplicity and compatibility with standard VCSEL fabrication processes.
Solution Approach 2:
The patent creates a dynamic feedback system by introducing the external resonator with optically discontinuous portions. This allows the laser to exhibit dynamic behavior where light feedback from the external resonator extends the modulation bandwidth. The system transitions from a static single-resonator structure to a dynamic coupled-resonator system that can respond to high-frequency modulation signals through the feedback mechanism.
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 extends modulation bandwidth, supports stable single-mode operation even with large oxide apertures, and improves noise characteristics, enabling high-output and reliable performance.
Implementation Method 1
a top Distributed Bragg Reflector (DBR)
Implementation Method 2
an optically discontinuous portion formed in the top DBR, wherein the optically discontinuous portion is arranged apart from the oxide aperture in a transverse direction
Implementation Method 3
a Vertical-Cavity Surface Emitting Laser (VCSEL) structure having a top Distributed Bragg Reflector (DBR)
Data Source
AI summary
A surface emitting laser has a Vertical-Cavity Surface emitting laser (VCSEL) structure. The VCSEL structure includes an aperture provided by a current confinement structure. An optically discontinuous portion is formed in a top Distributed Bragg Reflector (DBR) of the VCSEL structure such that it is arranged in a region with a gap between it and the aperture.