Bottom-Emitting VCSEL Reflective End for High Reflectivity
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Solution Overview
Problem
Existing bottom emitting VCSELs face challenges in achieving high reflectivity without increasing the thickness or mirror periods of the second mirror stack, which limits their optical efficiency.
Innovation Solution
Incorporating a phase matching layer and a first metal layer with individually selected thicknesses between the active region and the second mirror stack, allowing for improved reflectivity without altering the thickness or number of mirror periods, and using a metal stack with different layers to enhance reflection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness or mirror periods of the second mirror stack are increased to improve reflectivity, then the reflectivity is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the optical parameters of the existing mirror stack by introducing a phase matching layer with specific thickness (λ/4 or λ/2) and modifying the refractive index distribution. This allows the same physical structure to achieve higher reflectivity through parameter optimization rather than structural expansion
Solution Approach 2:
The patent creates a composite optical structure by combining the phase matching layer with the existing mirror stack. The phase matching layer acts as an intermediary optical element that enhances the overall reflectivity when combined with the mirror stack, achieving superior performance without increasing the number of mirror periods
2Reliability
If the thickness of the second mirror stack is increased to improve reflectivity, then the reflectivity is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the thickness parameter of the phase matching layer to specific values (λ/4 or λ/2) that provide enhanced reflectivity with tolerance to manufacturing variations. These specific thickness values create constructive interference patterns that are robust to small dimensional variations, reducing the precision requirements compared to increasing mirror stack thickness
3Reliability
If additional mirror periods are added to improve reflectivity, then the reflectivity is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent achieves improved reflectivity by optimizing the thickness parameter of the phase matching layer rather than adding more mirror periods. This approach maintains the same fabrication process complexity while achieving the desired optical performance through parameter optimization
Solution Approach 2:
The phase matching layer acts as an intermediary optical element between the active region and the mirror stack. This intermediate layer enhances the overall reflectivity by creating favorable phase conditions for light reflection, avoiding the need to modify the existing mirror stack structure
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 achieves a reflectivity of at least a predetermined threshold, optimizing reflectivity and slope efficiency for the VCSEL without increasing the structural complexity, thereby enhancing the device's performance.
Implementation Method 1
a reflective end configured to reflect the laser light toward the substrate
Implementation Method 2
a phase matching layer with a phase matching layer thickness... the phase matching layer thickness and first metal layer thickness have a combined thickness for the reflective end to have a reflectivity of at least a predetermined reflectivity threshold
Data Source
AI summary
A VCSEL can include: a substrate that passes light therethrough; a phase matching layer over a top mirror stack; a first metal layer over the phase matching layer; and an end metal region over the first metal layer. The phase matching layer and first metal layer have a cooperative thickness to provide reflectivity of at least a predetermined reflectivity threshold for the emission wavelength. A method of making a VCSEL can include: providing a substrate; forming a first mirror stack above the substrate; forming an active region above the first mirror stack; and forming a reflective end above the active region, the reflective end having a phase matching layer and a first metal layer. The phase matching layer and first metal layer have a combined thickness for the reflective end to have a reflectivity of at least a predetermined reflectivity threshold for an emission wavelength of the VCSEL.