Multi-Wavelength VCSEL Array Using Etched Optical Layer Features
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Solution Overview
Problem
The fabrication of a VCSEL array capable of emitting multiple wavelengths is challenging due to the complexity of existing methods, which often require precise control of growth rates and alignment, limiting the density and practicality of such arrays in large-scale production.
Innovation Solution
A method involving the formation of dimensioned features on the optical layer of a VCSEL, which are etched and then overgrown to create variations in refractive index and thickness, allowing for multiple wavelengths to be generated without the need for complex growth rate tuning or alignment, enabling flexible control of output wavelengths in a single etching step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If graded thickness layers are used to create multiple wavelengths, then wavelength variety is improved, but manufacturing precision and fabrication complexity worsen
Solution Approach 1:
The patent changes the parameter of cavity thickness by introducing dimensioned features (such as trenches or ridges) with specific depths and widths into the optical layer. These features create local variations in cavity thickness that determine different laser wavelengths for different emitters in the array, eliminating the need for complex graded thickness growth
Solution Approach 2:
The optical layer is segmented into regions with different dimensioned features, where each feature pattern corresponds to a specific wavelength. This segmentation allows independent control of wavelength for each emitter group while using standard fabrication processes
2Adaptability or versatility
If growth rate tuning is used to achieve multiple wavelengths, then wavelength control is improved, but device complexity and alignment requirements worsen
Solution Approach 1:
The dimensioned features are formed in the optical layer before the final epitaxial growth is completed. This preliminary action allows the cavity structure to be pre-configured with wavelength-determining features, simplifying subsequent fabrication steps and eliminating the need for complex growth rate tuning
Solution Approach 2:
The patent replaces the mechanical/control system of growth rate tuning with a geometric system of dimensioned features. Instead of dynamically controlling growth rates during epitaxy, the wavelength is determined by the static geometric dimensions of the features, which can be fabricated using standard lithography and etching processes
3Ease of manufacture
If standard VCSEL fabrication processes are used, then ease of manufacture is improved, but wavelength variety and control worsen
Solution Approach 1:
The dimensioned features serve multiple functions: they define the cavity structure, determine the laser wavelength, and can also serve as current confinement regions. This multi-functionality allows standard VCSEL fabrication processes to produce wavelength-tunable devices without requiring separate wavelength-control steps
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 approach simplifies the fabrication process, allows for dense VCSEL arrays with defined wavelengths, and enables standard VCSEL fabrication processes to be used, overcoming the limitations of previous methods by reducing the complexity of wavelength control and emitter spacing.
Implementation Method 1
Each of the DBRs consist of layers having alternating high and low refractive indices, and each layer has a thickness of a quarter of the laser wavelength in the material
Implementation Method 2
The optical layer has an active region and variations in refractive index and thickness
Data Source
AI summary
A vertical cavity surface emitting laser (VCSEL) array is fabricated to produce multiple wavelengths. A first distributed Bragg reflector (DBR) is formed on a substrate, and an optical layer having an active region is formed on the first DBR. The optical layer has a variation in optical characteristic configured to generate multiple wavelengths. To do this, a first portion of the layer is formed on the first DBR. Different dimensioned features (profiles, wells, trenches, gratings, etc.) are then formed on a surface of the first portion. Subsequently, a second portion of the layer is formed by filling in the dimensioned features on the first portion's surface. Finally, a second DBR is formed on the second portion of the layer. The variation in optical characteristic can include variation in refractive index, physical thickness, or both. The assembly can be processed as usual to produce a VCSEL array having multiple emitters.