Bottom Emitting VCSEL High Contrast Grating Mirror
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Solution Overview
Problem
Current bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) face challenges in improving reflectivity and manufacturing quality while reducing complexity and costs, particularly in the top mirror portion of the VCSEL structure.
Innovation Solution
The VCSEL structure incorporates a high contrast grating mirror or a dielectric-enhanced metal mirror, replacing a significant portion of the p-doped distributed Bragg reflector (pDBR) layers, and includes additional layers for hermetic and optical sealing, allowing for flip-chip bonding to an organic substrate, thereby enhancing reflectivity and reducing the number of semiconductor layers needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pDBR designs are used in bottom-emitting VCSELs, then sufficient reflectivity can be achieved, but the number of semiconductor layers increases manufacturing complexity and costs
Solution Approach 1:
The patent changes the optical parameters of the mirror structure by introducing high contrast gratings with specific geometric parameters (depth, width, period) and dielectric layers with optimized thicknesses. These parameter changes enable achieving the required reflectivity with fewer semiconductor layers compared to conventional pDBR designs, thereby reducing manufacturing complexity while maintaining reflectivity performance
Solution Approach 2:
The patent employs composite mirror structures combining semiconductor high contrast gratings with dielectric materials (such as silicon dioxide, silicon nitride, or silicon oxynitride). This composite approach leverages the high refractive index contrast of the grating structure and the optical properties of dielectric layers to achieve enhanced reflectivity with reduced layer count, resolving the contradiction between reflectivity requirements and manufacturing complexity
2Ease of manufacture
If the number of semiconductor layers is reduced to simplify manufacturing, then manufacturing complexity and costs decrease, but reflectivity may be compromised
Solution Approach 1:
By optimizing the geometric parameters of the high contrast grating (depth between 0.5-2.0 micrometers, width and period ratios) and dielectric layer thicknesses, the patent achieves high reflectivity (>90%) with a reduced number of semiconductor layers. This parameter optimization ensures that manufacturing is simplified while reflectivity requirements are met or exceeded
Solution Approach 2:
The patent substitutes traditional mechanical/structural approaches (stacking many semiconductor layers to achieve reflectivity) with optical approaches (using high contrast grating patterns and dielectric enhancements). This substitution reduces the number of semiconductor layers needed while maintaining or improving reflectivity, thereby easing manufacturing complexity without compromising optical performance
3Manufacturing precision
If conventional mirror structures are used, then manufacturing processes are well-established, but manufacturing quality and reflectivity performance can be improved
Solution Approach 1:
The patent introduces precisely controlled geometric parameters in the high contrast grating structure (depth, width, period, duty cycle) and dielectric layer thicknesses. These parameter changes enable superior manufacturing quality and reflectivity performance by creating optimized optical paths and interference patterns, while the added structural complexity is offset by the precision and controllability of the fabrication processes
Solution Approach 2:
The high contrast grating structure can be fabricated using standard lithographic and etching processes that are well-established in the semiconductor industry. By copying proven fabrication techniques and optimizing their parameters, the patent achieves high manufacturing quality without requiring entirely new manufacturing approaches, thereby improving performance while managing complexity
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 results in improved reflectivity, reduced manufacturing complexity and costs, and enhanced manufacturing quality by reducing the number of semiconductor layers required for reflectivity, while maintaining or exceeding the reflectivity characteristics of conventional pDBR designs.
Implementation Method 1
an n-doped distributed Bragg reflector (nDBR)... a p-doped distributed Bragg reflector (pDBR)
Implementation Method 2
the active region may be pumped (e.g., electrically or optically) with a pumping energy to produce photons, some of which resonate and build up to form coherent light
Implementation Method 3
The VCSEL structure includes an active region disposed in the laser cavity... at least one of a high contrast grating mirror and a dielectric-enhanced metal mirror
Data Source
Figure 1
Figure 2
AI summary
A bottom-emitting vertical-cavity surface-emitting laser (VCSEL) structure includes a first substrate permitting the passage of light therethrough, an n-doped distributed Bragg reflector (nDBR), a p-doped distributed Bragg reflector (pDBR), one or more active layers, at least one of a high contrast grating mirror and a dielectric-enhanced metal mirror, and a plurality of layers, where the VCSEL structure is configured to be flip chipped to a second substrate. The pDBR and the nDBR define a laser cavity extending vertically therebetween and containing the one or more active layers. The at least one of a high contrast grating mirror and a dielectric-enhanced metal mirror may be disposed over the pDBR. The plurality of layers may be disposed over the at least one of the high contrast grating mirror and the dielectric-enhanced metal mirror to optically and hermetically seal the laser cavity.