Small-Mode-Volume VCSEL With Nested DBR Layers
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Solution Overview
Problem
Conventional vertical-cavity, surface-emitting lasers (VCSELs) face challenges in reducing series electrical resistance and achieving high modulation bandwidth, low power dissipation, and thermal stability while maintaining stable output amplitude and low frequency drift.
Innovation Solution
The integration of an active structure within either a distributed Bragg reflector (DBR) or a grating reflector structure in VCSELs, along with a spacer layer, reduces the total thickness and series electrical resistance, enabling high bandwidth and thermal stability through novel carrier injection schemes and geometrical arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the total thickness of VCSEL is reduced, then series electrical resistance decreases and bandwidth increases, but thermal stability and output amplitude stability become more difficult to maintain
Solution Approach 1:
The active structure is nested within the distributed Bragg reflector (DBR) layers, specifically positioned within the high-index alternating layers. This nesting arrangement reduces the overall cavity thickness and series electrical resistance while maintaining the optical feedback mechanism through the DBR's distributed reflection, thereby achieving high bandwidth without sacrificing thermal stability
Solution Approach 2:
The DBR structure acts as an intermediary between the active region and the external environment, providing optical confinement and feedback while the reduced cavity thickness minimizes electrical resistance. The DBR's periodic structure mediates the trade-off by maintaining optical performance with reduced physical dimensions
2Loss of energy
If the total thickness of VCSEL is reduced, then series electrical resistance decreases, but power dissipation and frequency drift control become more challenging
Solution Approach 1:
By nesting the active structure within the DBR layers, the patent achieves minimal cavity thickness which reduces series electrical resistance and power dissipation. The DBR's distributed Bragg reflection provides sufficient optical feedback to maintain frequency stability despite the reduced thickness
Solution Approach 2:
The patent optimizes the DBR layer parameters (refractive index contrast, layer thickness, number of periods) to maintain frequency stability while minimizing the overall device thickness. By carefully controlling these parameters, the system achieves low series resistance without compromising frequency drift control
3Ease of manufacture
If conventional VCSEL structure is used, then fabrication is straightforward, but series electrical resistance is high and bandwidth is limited
Solution Approach 1:
The patent merges the active structure with the DBR layers, eliminating the need for separate cavity formation steps. This integration maintains wafer-level batch fabrication compatibility while achieving reduced thickness and lower series electrical resistance, thereby increasing modulation bandwidth without complicating the manufacturing process
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 VCSELs with high bandwidth, low power dissipation, high thermal stability, stable output amplitude, and reduced frequency drift, making them suitable for data-communication applications.
Implementation Method 1
two reflecting structures at least one of which is a grating reflector structure. In one or more examples of the present invention, the small-mode-volume VCSEL includes a distributed Bragg reflector being the other of the two reflecting structures
Implementation Method 2
an active structure to emit light upon injection of carriers
Data Source
AI summary
A small-mode-volume, vertical-cavity, surface-emitting laser (VCSEL). The VCSEL includes an active structure to emit light upon injection of carriers, and two reflecting structures at least one of which is a grating reflector structure. The active structure is disposed within at least one of the reflecting structures. The reflecting structures are configured as a vertical-cavity resonator of small mode-volume. An optical-bus transmitter including a plurality of small-mode-volume VCSELs, and a system including at least one optical bus and at least one optical-bus transmitter in a digital-information processor, or a data-processing center, are also provided.