VCSEL High-Contrast Grating Passivation for Reliable Air-Gap Optics
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Solution Overview
Problem
Existing vertical-cavity surface-emitting lasers (VCSELs) face challenges in achieving optimal performance and reliability due to limitations in their design, particularly with the use of high-contrast grating (HCG) structures, where the passivation layer thickness and air gaps between grating elements affect the device's efficiency and reliability.
Innovation Solution
A VCSEL design is proposed with a thicker passivation layer on the top surfaces of grating elements compared to the sidewalls and air gaps between them, enhancing the reliability and performance by optimizing the thickness ratio and deposition processes to balance power and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the passivation layer thickness is increased on the top surfaces of grating elements, then the reliability and protection of the HCG structure is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies local quality by varying the passivation layer thickness across different locations of the grating structure. The top surfaces of grating elements receive a thicker passivation layer for enhanced protection, while the air gaps between elements maintain a thinner layer. This spatially differentiated approach optimizes reliability at critical locations without uniformly increasing device complexity throughout the entire structure.
2Reliability
If the passivation layer thickness is increased on the top surfaces of grating elements, then the protection of the HCG structure is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent implements local quality by depositing the passivation layer with spatially varying thickness characteristics. The deposition process is configured to naturally form thicker regions on top surfaces and thinner regions in air gaps through geometric shadowing and surface orientation effects. This approach achieves differentiated protection levels without requiring complex multi-step deposition or precise manual control at each location, thereby managing manufacturing precision requirements.
3Power
If the air gaps between grating elements are maintained, then the optical performance is improved, but the reliability and protection of the structure deteriorates
Solution Approach 1:
The patent resolves this contradiction by applying local quality to the passivation layer distribution. The air gaps between grating elements maintain their essential optical function while receiving a thinner passivation layer coating, whereas the top surfaces of grating elements receive thicker protection. This localized differentiation allows the structure to simultaneously achieve adequate optical performance through air gap maintenance and sufficient reliability through enhanced protection at critical exposed surfaces.
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 design improves the reliability and maintains performance by ensuring the passivation layer effectively protects the HCG structure, enhancing the VCSEL's operational stability and efficiency.
Implementation Method 1
The passivation layer over the HCG in the HCG VCSEL device may be necessary to protect the underlying structure
Implementation Method 2
The oxide layer is disposed on the active layer
Data Source
AI summary
A vertical-cavity surface-emitting laser includes a substrate. A first mirror is disposed on the substrate. An active layer is disposed on the first mirror. An oxide layer is disposed on the active layer. An aperture is disposed on the active layer. The aperture is surrounded by the oxide layer. A second mirror is disposed on the aperture and the oxide layer. A high-contrast grating is disposed on the second mirror. The high-contrast grating includes a first grating element and a second grating element, and the first grating element and the second grating element are spaced apart from each other with an air gap therebetween. A passivation layer is disposed on the high-contrast grating. A first thickness of the passivation layer on a top surface of the first grating element is greater than a second thickness of the passivation layer on a first sidewall of the first grating element.