Coupled-Cavity VCSEL Modulation Bandwidth via External Resonance
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Solution Overview
Problem
Vertical cavity surface emitting lasers (VCSELs) are limited in modulation bandwidth due to their size, with current approaches requiring complex fabrication and combination of multiple devices to enhance bandwidth, whereas the technology aims to increase bandwidth without redesigning the VCSEL structure or increasing its size.
Innovation Solution
The technology introduces an external cavity coupled to the internal lasing cavity of a single VCSEL, where the external cavity is tuned to resonate near the VCSEL's wavelength, increasing the overall modulation bandwidth through photon-photon resonance without the need for additional VCSELs or increased device size, using a shared mirror and feedback loops for optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the size of the VCSEL is increased to enhance modulation bandwidth, then the modulation bandwidth is improved, but the device complexity and fabrication difficulty increase
Solution Approach 1:
The patent embeds an external cavity within the existing VCSEL structure, creating a nested configuration where the external cavity is coupled to the internal lasing cavity. This allows the bandwidth enhancement functionality to be integrated without significantly increasing the overall device footprint or fabrication complexity, as the external cavity utilizes the existing VCSEL cavity as part of its structure
Solution Approach 2:
The patent extends the optical path by adding an external cavity that operates in a different spatial dimension or configuration compared to the internal lasing cavity. This dimensional extension allows the modulation bandwidth to be enhanced without proportionally increasing the physical size of the VCSEL core structure
2Speed
If multiple VCSELs are combined to increase modulation bandwidth, then the bandwidth is improved, but the fabrication complexity and device integration difficulty increase
Solution Approach 1:
The patent divides the optical cavity into two functional segments: the internal lasing cavity for light generation and the external cavity for bandwidth enhancement. This segmentation allows each part to be optimized independently while maintaining a relatively simple fabrication process compared to combining multiple complete VCSEL devices
Solution Approach 2:
The patent merges the external cavity with the internal lasing cavity to form a coupled-cavity system. This combination achieves the bandwidth enhancement of multiple devices while maintaining a single integrated structure that is easier to fabricate than multiple separate VCSELs
3Speed
If the VCSEL structure is redesigned to enhance bandwidth, then the modulation bandwidth is improved, but the device complexity and design requirements increase
Solution Approach 1:
The patent introduces dynamic coupling between the internal and external cavities, where the coupling strength can be adjusted by modifying the separation distance or optical coupling conditions. This dynamic aspect allows bandwidth tuning without requiring complete structural redesign of the VCSEL
Solution Approach 2:
The patent achieves bandwidth enhancement by changing key parameters such as the external cavity length, mirror reflectivities, and coupling conditions, rather than fundamentally redesigning the VCSEL structure. These parameter adjustments allow bandwidth optimization while maintaining the core VCSEL architecture
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 effectively enhances the modulation bandwidth of VCSELs beyond the intrinsic limit of 20-25 GHz, achieving higher performance without increasing power consumption or device complexity, applicable to both top- and bottom-emitting VCSELs.
Implementation Method 1
The external cavity and a lasing cavity of the single VSCSEL create a coupled cavity for the VCSEL, where the external cavity and the lasing cavity share a mirror. The external cavity is tuned to come close to a resonance wavelength of the VCSEL structure, enabling coupling between the resonance of the internal lasing cavity of the VCSEL structure and the external cavity.
Data Source
AI summary
Coupled-cavity vertical cavity surface emitting lasers (VCSELs) are provided by the present disclosure. The coupled-cavity VCSEL can comprise a VCSEL having a first mirror, a gain medium disposed above the first mirror, and a second mirror disposed above the gain medium, wherein a first cavity is formed by the first mirror and the second mirror. A second cavity is optically coupled to the VCSEL and configured to reflect light emitted from the VCSEL back into the first cavity of the VCSEL. In some embodiments, the second cavity can be an external cavity optically coupled to the VCSEL through a coupling component. In some embodiments, the second cavity can be integrated with the VCSEL to form a monolithic coupled-cavity VCSEL. A feedback circuit can control operation of the coupled-cavity VCSEL so the output comprises a target high frequency signal.