VCSEL Optical Confinement Reducing Region
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Solution Overview
Problem
Vertical cavity surface emitting laser devices exhibit a negative droop characteristic, leading to poor image quality due to changes in optical output during the rise time of the optical waveform, and the optical thickness of low refractive index layers in semiconductor multilayer reflectors increases absorption, affecting slope efficiency and threshold current.
Innovation Solution
The introduction of an optical confinement reducing region in the lower semiconductor DBR and an absorption loss reducing layer, along with a selective oxidation layer, to reduce optical confinement and absorption loss, thereby suppressing the negative droop characteristic and enhancing single fundamental transverse-mode output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the optical thickness of low refractive index layers is increased to reduce absorption loss, then absorption loss is reduced, but the threshold current increases and slope efficiency decreases
Solution Approach 1:
The patent changes the optical thickness parameter of the low refractive index layers from the conventional λ/4 to 3λ/4. This parameter change reduces absorption loss by positioning the electric field nodes differently within the layer structure, while the overall device design compensates for the resulting increase in threshold current through optimized active layer and reflector configurations.
Solution Approach 2:
The patent applies local quality by creating distinct functional regions within the DBR structure. The lower semiconductor DBR contains layers with optical thickness of 3λ/4 specifically positioned to reduce absorption loss in high-field regions, while other layers maintain conventional thickness. This localized optimization allows absorption reduction without uniformly increasing threshold current across the entire device.
2Stability of the object's composition
If oxide confinement is strengthened to improve transverse mode confinement, then mode stability is improved, but higher-order mode oscillation is suppressed and single fundamental mode operation becomes difficult
Solution Approach 1:
The patent modifies the oxide confinement parameters by reducing the oxide thickness and/or increasing the distance between the oxide layer and the active layer. This parameter change weakens the transverse mode confinement strength, allowing the fundamental mode to oscillate without excessive confinement that would suppress higher-order modes entirely, thereby enabling stable single-mode operation.
Solution Approach 2:
The patent applies partial oxidation rather than complete or excessive oxidation. By providing oxide layers with controlled, reduced thickness or positioning them at optimized distances from the active layer, the patent achieves sufficient mode confinement for stability while avoiding excessive confinement that would prevent single-mode operation. This partial action approach balances both requirements.
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 effectively suppresses the negative droop characteristic, improves image quality by stabilizing the optical output during the rise time, and increases the single fundamental transverse-mode output while maintaining high luminous efficiency and temperature characteristics.
Implementation Method 1
oxide-confined vertical cavity surface emitting laser devices have an advantage of having favorable transverse mode confinement provided by an oxide
Implementation Method 2
A commonly used current confinement structure is formed through selective oxidation of an AlAs (aluminum arsenide) layer
Implementation Method 3
vertical cavity surface emitting laser device which emits light orthogonally in relation to a substrate
Data Source
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AI summary
A disclosed vertical cavity surface emitting laser device emits light orthogonally in relation to a substrate and includes a resonator structure including an active layer; and semiconductor multilayer reflectors disposed in such a manner as to sandwich the resonator structure between them and including a confinement structure which confines an injected current and transverse modes of oscillation light at the same time. The confinement structure has an oxidized region which surrounds a current passage region. The oxidized region is formed by oxidizing a part of a selective oxidation layer which includes aluminum and includes at least an oxide. The selective oxidation layer is at least 25 nm in thickness. The semiconductor multilayer reflectors include an optical confinement reducing section which reduces optical confinement in a transverse direction. The optical confinement reducing section is disposed on the substrate side in relation to the resonator structure.