VCSEL Tunnel Junction Mesa Etching for Mode and Current Confinement
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Solution Overview
Problem
Conventional vertical-cavity surface-emitting lasers (VCSELs) face challenges in accurately confining current density and optical field, making them unsuitable for high-speed and long-reach optical fiber transmission due to optical mode dispersion and low output power.
Innovation Solution
The introduction of a tunnel junction with a p-type material and an n-type material, where the n-type material is etched to form a mesa region with a sloped outer edge and openings, creating a change in refractive index that enhances optical and current confinement by increasing the overlap of current density and optical field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional VCSEL structure is used, then device simplicity is maintained, but optical and current confinement is insufficient leading to mode dispersion and low output power
Solution Approach 1:
The tunnel junction is segmented into a p-type material region and an n-type material region with different cross-sectional areas. The n-type region has a smaller area than the p-type region, creating distinct functional zones that improve current confinement while maintaining structural manageability
Solution Approach 2:
The patent applies local quality by creating a refractive index gradient within the tunnel junction structure. The change in refractive index from the p-type to n-type material regions provides localized optical confinement exactly where needed at the quantum well interface, without requiring complex structures throughout the entire device
2Manufacturing precision
If tunnel junction with refractive index change is implemented, then optical confinement is improved, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes parameter changes by varying the refractive index through material composition changes in the tunnel junction. The p-type and n-type materials have different refractive indices, creating an optical aperture through material property modification rather than complex geometric structuring, which simplifies manufacturing while achieving precise optical confinement
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 improves the optical power and reliability of VCSELs by enhancing current and optical field confinement, enabling high-speed transmission and reducing modal dispersion.
Implementation Method 1
The p-type material and the n-type material may be configured to provide a change in refractive index from the maximum outer dimension over a distance toward the optical axis, and the change in the refractive index may form an optical aperture of the laser
Implementation Method 2
The quantum well may be configured to emit light and define a quantum well plane
Data Source
AI summary
Some embodiments of the present invention are directed to a tunnel junction for a vertical-cavity surface-emitting laser (VCSEL) that controls optical and current confinement within the VCSEL. The tunnel junction may define an electrical current injection area and an optical aperture for the VCSEL and may include a heavily p++ doped p-type material and a heavily n++ doped n-type material disposed on the p-type material. At least a portion of the outer edges of the n-type material are etched such that the n-type material has a cross-sectional area that is less than a cross-sectional area of the p-type material. By removing a portion of n-type material near the outer edge of the tunnel junction, a sloped effective refractive index is formed, and an effective area of the tunnel junction is changed, which increases the overlap of the current density and the optical field of the VCSEL.