VCSEL Lateral Feedback Cavity Modulation Speed
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Solution Overview
Problem
Existing VCSEL technologies face limitations in modulation speed due to restricted three dB bandwidth and resonance peak, often being constrained by relaxation oscillation frequency and lacking effective feedback biasing mechanisms.
Innovation Solution
A coupled cavity VCSEL design incorporating a bottom and top DBR mirror with a vertical optical cavity and a lateral feedback optical cavity, where an oxide layer defines an aperture and an isolation implant electrically isolates these cavities, allowing for feedback biasing to adjust the optical signal, thereby enhancing modulation response, three dB bandwidth, and resonance peak.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional VCSEL design is used, then the structure is simple, but the modulation speed is limited due to restricted three dB bandwidth and resonance peak
Solution Approach 1:
The VCSEL cavity is segmented into two distinct cavities: a vertical optical cavity for light emission and a lateral feedback optical cavity for feedback biasing. This segmentation allows independent optimization of each cavity's function, enabling enhanced modulation speed through the lateral cavity while maintaining the primary lasing function in the vertical cavity.
Solution Approach 2:
An oxide layer is introduced as an intermediary element that defines an aperture and provides electrical isolation between the vertical and lateral cavities. This intermediary structure enables optical coupling between cavities while preventing electrical interference, allowing the feedback mechanism to operate without compromising the main lasing cavity's performance.
2Productivity
If feedback biasing is added to adjust optical signal, then modulation response and three dB bandwidth are enhanced, but device complexity increases
Solution Approach 1:
The patent merges the feedback mechanism directly into the laser cavity structure by forming a lateral feedback optical cavity within the same VCSEL device. This integration allows the feedback biasing to be implemented without requiring external components, enhancing modulation response while keeping the overall device structure compact and unified.
Solution Approach 2:
Instead of adding feedback along the vertical axis of the VCSEL, the patent introduces a lateral feedback cavity in the horizontal dimension. This dimensional transition allows feedback injection into the vertical cavity from the side, enabling independent control of feedback strength through lateral cavity design parameters without interfering with the vertical lasing mode.
3Reliability
If isolation implant is used to electrically isolate cavities, then optical signal stability is improved, but manufacturing complexity increases
Solution Approach 1:
The oxide layer performs multiple functions simultaneously: it defines the aperture for optical confinement, provides electrical isolation between the vertical and lateral cavities, and enables optical coupling between the two cavities. This self-service approach consolidates multiple required functions into a single structure, improving reliability without proportionally increasing manufacturing complexity.
Solution Approach 2:
The isolation implant serves multiple purposes: it provides electrical isolation between different cavity regions, creates aperture structures for optical confinement, and enables independent biasing of the lateral feedback cavity. This multi-functionality reduces the need for separate components for each function, balancing reliability improvement with manufacturing feasibility.
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 increases modulation speed by optimizing the three dB bandwidth and resonance peak, reducing limitations imposed by relaxation oscillation frequency and improving optical signal transmission efficiency.
Implementation Method 1
a bottom distributed Bragg reflector (DBR) mirror. The coupled cavity VCSEL may also include a top DBR mirror formed above the bottom DBR mirror
Implementation Method 2
a vertical optical cavity located within a portion of the bottom DBR mirror and a portion of the top DBR mirror. The vertical optical cavity may be configured to emit an optical signal
Implementation Method 3
The lateral feedback optical cavity may be configured to receive a feedback bias signal to bias the lateral feedback optical cavity to adjust the optical signal
Implementation Method 4
an active region formed between the bottom DBR mirror and the top DBR mirror
Implementation Method 5
The active region may include an oxide layer that defines an oxide aperture
Implementation Method 6
an isolation implant. The isolation implant may be configured to electrically isolate the vertical optical cavity from the lateral feedback optical cavity
Data Source
AI summary
A VCSEL may include a bottom DBR mirror and a top DBR mirror above the bottom DBR mirror. The VCSEL may include a vertical optical cavity located within a portion of the bottom and top DBR mirrors. The vertical optical cavity may be configured to emit an optical signal. The VCSEL may include a lateral feedback optical cavity located within a different portion of the bottom and the top DBR mirrors configured to receive a feedback bias signal configured to bias the lateral feedback optical cavity to adjust the optical signal. The VCSEL may include an active region formed between the bottom and the top DBR mirrors that may include an oxide layer defining an oxide aperture. The VCSEL may include an isolation implant configured to electrically isolate the vertical optical cavity from the feedback optical cavity and to create a first and a second aperture within the oxide aperture.