Multi-Layer Oxide Aperture VCSEL for Side-Mode Suppression
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Solution Overview
Problem
High-speed and high-volume data communication demands require optics-based solutions with lasers that effectively suppress side-modes and maintain longitudinal confinement, but existing oxide apertures in VCSELs face challenges in balancing spectral width and high-speed performance due to oxidation effects, leading to high electrical resistance and sensitivity to mode filter diameter and drive current.
Innovation Solution
A multi-layer oxide aperture in a mode-filtered vertical-cavity surface-emitting laser (VCSEL) with epitaxial layers of varying aluminum fractions, where the third layer is oxidized to form a thin oxide aperture, maintaining strong longitudinal confinement and increasing side-mode suppression ratio, while preventing oxidation of adjacent layers to minimize distortion and maintain high-speed performance across a range of currents and mode-filter diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional oxide aperture is used in VCSEL, then side-mode suppression is achieved, but electrical resistance increases and high-speed performance deteriorates
Solution Approach 1:
The oxide aperture is divided into multiple segments along the optical axis, with each segment having different aluminum fractions. This segmentation allows selective oxidation of specific layers while preserving others, achieving side-mode suppression through the oxidized portions while maintaining low electrical resistance through the unoxidized portions.
Solution Approach 2:
Different portions of the mirror layer are assigned different aluminum fractions to create local quality variations. The first portion has high aluminum fraction for strong longitudinal confinement, the second portion has low aluminum fraction for low electrical resistance, and the third portion has high aluminum fraction for side-mode suppression when oxidized.
2Reliability
If oxide aperture thickness is increased to improve side-mode suppression, then spectral width is reduced, but sensitivity to mode filter diameter and drive current increases
Solution Approach 1:
The solution moves from controlling side-mode suppression through a single thickness parameter to controlling it through the aluminum fraction composition parameter. By varying the aluminum fraction in different portions, the oxide aperture achieves side-mode suppression while maintaining low sensitivity to mode filter diameter and drive current variations.
3Reliability
If aluminum fraction is increased to enhance longitudinal confinement, then optical field confinement is improved, but oxidation resistance decreases leading to aperture distortion
Solution Approach 1:
The mirror layer is segmented into multiple portions with different aluminum fractions positioned at different locations along the optical axis. The first portion with high aluminum fraction provides longitudinal confinement, while the second portion with low aluminum fraction positioned between the first and third portions protects against oxidation-induced distortion.
Solution Approach 2:
The second portion with low aluminum fraction acts as an intermediary layer between the first and third portions. This intermediate layer with low aluminum fraction serves as a buffer that prevents oxidation from propagating and causing distortion in the high aluminum fraction regions, thereby maintaining structural stability.
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 solution enhances side-mode suppression ratio and maintains high longitudinal confinement, allowing for flexible operation with various drive currents and mode-filter diameters, preserving high bandwidth and reducing electrical resistance, thus addressing the trade-offs in existing VCSEL designs.
Implementation Method 1
The aluminum in the third portion may be oxidized to form an oxide aperture
Implementation Method 2
The oxide aperture may be configured to increase a side-mode suppression ratio of the laser, and the first portion of the mirror layer may be configured to provide high longitudinal confinement of an optical field of the light
Data Source
AI summary
Some embodiments of the present invention are directed to a mode-filtered VCSEL having a multi-layer oxide aperture for high-bandwidth and side-mode suppression. The oxide aperture may include multiple layers having different aluminum fractions configured to increase an SMSR of the VCSEL while maintaining longitudinal confinement. The oxide aperture may be formed from a mirror layer of the VCSEL proximate an active region. The mirror layer may include first epitaxial layers closest to the active region having a first aluminum fraction selected to longitudinally confine the optical field of the VCSEL. The mirror layer may include second epitaxial layers having a second aluminum fraction low enough to prevent substantial oxidation of the second epitaxial layers. Additionally, the mirror layer may include third epitaxial layers having a third aluminum fraction greater than the first and second aluminum fractions. The third epitaxial layers may be oxidized to form the oxide aperture.