Hybrid VCSEL Mirror for Single-Mode Narrow Beam Divergence
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-contrast distributed Bragg reflectors in VCSELs lead to multiple longitudinal modes, causing unstable operation and undesirable beam characteristics such as broad spectral width and high beam divergence.
Innovation Solution
A hybrid mirror is introduced, combining a narrow bandwidth mirror with a high-reflectivity mirror within the laser cavity, along with phase-matching layers for constructive interference, to suppress unwanted modes and achieve a single-mode operation with reduced beam divergence and spectral width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high-contrast distributed Bragg reflector is used to achieve high reflectivity, then the reflectivity is improved, but the spectral width broadens and multiple longitudinal modes are generated
Solution Approach 1:
The distributed Bragg reflector is segmented into multiple alternating layers of high and low refractive index materials. This segmentation creates constructive interference at specific wavelengths while providing broad reflectivity, resolving the contradiction between high reflectivity and narrow spectral width by designing the layer structure to achieve both properties simultaneously
Solution Approach 2:
The optical parameters of the DBR layers (refractive index, layer thickness) are precisely controlled to achieve the desired reflectivity and spectral characteristics. By adjusting these parameters, the reflector provides high reflectivity at the target wavelength while maintaining a controlled spectral width that prevents excessive mode proliferation
2Use of energy by moving object
If a high-contrast distributed Bragg reflector is used to achieve high reflectivity, then the reflectivity is improved, but multiple longitudinal modes are generated causing unstable operation
Solution Approach 1:
An extended length mirror is introduced as an intermediary element between the high-contrast DBR and the active region. This extended mirror acts as a mode-selective filter that suppresses unwanted longitudinal modes while allowing the desired mode to lase, thereby maintaining operational stability while preserving the high reflectivity benefits of the DBR
Solution Approach 2:
The optical cavity is designed with dynamic mode selection capabilities through the extended length mirror, which preferentially supports certain longitudinal modes while suppressing others. This dynamic mode control ensures stable single-mode or few-mode operation despite the broad reflectivity band of the high-contrast DBR
3Quantity of substance
If multiple longitudinal modes are allowed to lase, then the beam spectral width increases, but the beam divergence remains high
Solution Approach 1:
The extended length mirror extracts or filters out the unwanted higher-order longitudinal modes from the lasing spectrum, allowing only the fundamental mode or selected modes to contribute to the output beam. This extraction of unwanted modes reduces the effective spectral width of the lasing emission and consequently reduces beam divergence
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 hybrid mirror effectively filters out higher-order transverse and longitudinal modes, resulting in a narrow beam divergence and uniform beam intensity, suitable for applications like LIDAR and high-bandwidth communications.
Implementation Method 1
distributed Bragg reflectors (DBR) (e.g., quarter-wave-thick layers of alternating high and low refractive indexes)
Implementation Method 2
The hybrid mirror and the high reflection mirror are operable to suppress one or more longitudinal and/or transverse modes
Data Source
AI summary
Narrow beam divergence semiconductor sources are operable to generate a beam having a substantially narrow beam divergence, an emission wavelength, and a substantially uniform beam intensity. The presence of an extended length mirror can help suppress one or more longitudinal and/or transverse modes such that the beam divergence and/or the spectral width of emission is substantially reduced.