VCSEL Extended Cavity Structure for Low-Divergence LiDAR Beams
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Solution Overview
Problem
Conventional VCSELs have a divergence angle of 20-30 degrees, which limits the detection range, resolution, and signal-to-noise ratio in new application scenes, such as three-dimensional sensors and laser radar, and lengthening the cavity to reduce divergence angle leads to issues like multiple longitudinal modes and decreased temperature stability.
Innovation Solution
A VCSEL design with a small divergence angle is achieved by incorporating an extended cavity layer with a resonant cavity between the Bragg reflection layers, increasing optical field intensity and reducing the difference in effective refractive indexes, thereby suppressing higher-order modes and achieving single longitudinal mode lasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the cavity length is increased to reduce the divergence angle, then the divergence angle is reduced, but multiple longitudinal modes are generated and temperature stability decreases
Solution Approach 1:
The cavity is segmented into a distributed Bragg reflector (DBR) structure with multiple alternating high-refractive-index and low-refractive-index layers. This segmentation creates a photonic bandgap that provides wavelength-selective feedback, enabling single longitudinal mode operation while maintaining a longer effective cavity length for reduced divergence angle.
Solution Approach 2:
The refractive index parameters of the DBR layers are optimized to create a photonic bandgap centered at the lasing wavelength. By changing the thickness and refractive index of alternating layers, the structure provides strong wavelength selectivity that suppresses multiple longitudinal modes while maintaining temperature stability through the photonic bandgap effect.
2Shape
If the cavity length is increased to reduce the divergence angle, then the divergence angle is reduced, but the detection range and resolution are limited
Solution Approach 1:
The cavity is segmented into a distributed Bragg reflector (DBR) structure with multiple alternating high-refractive-index and low-refractive-index layers. This segmentation creates a photonic bandgap that provides wavelength-selective feedback, enabling single longitudinal mode operation while maintaining a longer effective cavity length for reduced divergence angle.
Solution Approach 2:
The refractive index parameters of the DBR layers are optimized to create a photonic bandgap centered at the lasing wavelength. By changing the thickness and refractive index of alternating layers, the structure provides strong wavelength selectivity that suppresses multiple longitudinal modes while maintaining temperature stability through the photonic bandgap effect.
3Shape
If the divergence angle is reduced for new application scenes, then the beam quality is improved, but the signal-to-noise ratio is reduced
Solution Approach 1:
The cavity is segmented into a distributed Bragg reflector (DBR) structure with multiple alternating high-refractive-index and low-refractive-index layers. This segmentation creates a photonic bandgap that provides wavelength-selective feedback, enabling single longitudinal mode operation while maintaining a longer effective cavity length for reduced divergence angle.
Solution Approach 2:
The refractive index parameters of the DBR layers are optimized to create a photonic bandgap centered at the lasing wavelength. By changing the thickness and refractive index of alternating layers, the structure provides strong wavelength selectivity that suppresses multiple longitudinal modes while maintaining temperature stability through the photonic bandgap effect.
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 design significantly reduces the divergence angle to less than 20 degrees, avoiding multi-wavelength output and maintaining temperature stability, enhancing the efficiency and recognition of three-dimensional sensors and laser radar systems.
Implementation Method 1
An extended cavity layer is disposed at least between the lower Bragg reflection layer and the active layer or between the upper Bragg reflection layer and the active layer, the extended cavity layer includes at least one resonant cavity inside, and the at least one resonant cavity is configured to increase the optical field intensity in the extended cavity layer
Implementation Method 2
a lower Bragg reflection layer, an active layer and an upper Bragg reflection layer
Data Source
AI summary
A VCSEL includes a lower Bragg reflection layer, an active layer and an upper Bragg reflection layer. The active layer is located on a side of the lower Bragg reflection layer. The upper Bragg reflection layer is located on a side of the active layer away from the lower Bragg reflection layer. A current limiting layer is disposed inside or outside the active layer, and the current limiting layer has an opening for defining a light-emitting region. An extended cavity layer is disposed at least between the lower Bragg reflection layer and the active layer or between the upper Bragg reflection layer and the active layer, the extended cavity layer includes at least one resonant cavity inside, and the at least one resonant cavity is configured to increase the optical field intensity in the extended cavity layer.