Dielectric Current Confinement Ridge Waveguide Laser Bandwidth
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Solution Overview
Problem
Direct modulated lasers (DMLs) face challenges in scaling to achieve production bandwidths greater than 35 GHz for 100 Gbps per lambda transmission due to limitations in frequency response, which are affected by relaxation oscillation frequency, damping, and resistance, leading to issues like current spreading, optical scattering loss, and high threshold current density.
Innovation Solution
A DML with a dielectric current confinement ridge waveguide structure is developed, featuring a mesa structure with an increased width of 1.3 to 2.5 microns, formed using selective area regrowth via metalorganic chemical vapor deposition (MOCVD), which reduces current spreading and electrical resistance, and enhances optical confinement and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the active region volume is decreased to increase frequency response, then the bandwidth is improved, but the cleaving yield deteriorates
Solution Approach 1:
The patent transitions from reducing active region volume (3D approach) to reducing active region width (1D approach). By maintaining length and thickness while narrowing the width to 1.5±0.2 microns, the invention achieves frequency response improvement without compromising cleving yield, as the length remains sufficient for reliable cleaving.
Solution Approach 2:
The patent applies local quality by creating a narrow ridge waveguide structure with precise width control (1.5±0.2 microns) in the active region, while maintaining standard dimensions in other areas. This localized dimensional control achieves the desired frequency response without globally reducing the device dimensions that would affect cleving yield.
2Speed
If the mesa width is reduced to decrease active region volume, then the frequency response is improved, but the electrical resistance increases
Solution Approach 1:
The patent optimizes the mesa width parameter to a specific range (1.3 to 2.5 microns, preferably 1.5±0.2 microns) that balances frequency response and electrical resistance. This precise parameter control allows the device to achieve high bandwidth while maintaining acceptable resistance levels through optimized current confinement.
Solution Approach 2:
The narrow ridge waveguide structure creates localized current confinement in the active region, concentrating the current flow through the optimized width path. This local quality enhancement improves frequency response while the overall device structure maintains sufficient current pathways to manage electrical resistance.
3Speed
If the active region width is reduced to increase optical confinement, then the frequency response is improved, but the current spreading increases
Solution Approach 1:
The patent implements local quality through the narrow ridge waveguide structure (1.5±0.2 microns width) that provides both optical confinement and current confinement in the same localized region. This dual confinement approach ensures that current is guided through the narrow active region without excessive spreading, while still achieving the optical confinement needed for high frequency response.
Solution Approach 2:
The ridge waveguide structure combines semiconductor materials with precisely controlled dimensions to create a composite structure that simultaneously provides optical confinement and current confinement. The layered semiconductor structure with the narrow ridge geometry works together to achieve both optical and electrical performance goals.
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
The dielectric current confinement ridge waveguide structure minimizes current spreading, reduces electrical resistance, and increases optical confinement, thereby improving the frequency response and efficiency of the DML, addressing the limitations of existing DML configurations.
Implementation Method 1
reduces current spreading and electrical resistance
Implementation Method 2
increases optical confinement
Implementation Method 3
formed using selective area regrowth via metalorganic chemical vapor deposition (MOCVD)
Implementation Method 4
enhances optical confinement and thermal conductivity
Data Source
AI summary
An aspect of the present disclosure includes a direct modulated laser (DML) with a dielectric current confinement ridge waveguide (RWG) structure. The DML comprises a substrate, one or more layers of material disposed on the substrate to provide a multi quantum well (MQW), first and second insulation/dielectric structures disposed on opposite sides of the MQW, and one or more layers of material disposed on the MQW to provide a mesa structure for receiving a driving current. The mesa structure is preferably disposed between the first and second insulation structures to provide a dielectric current confinement (RWG) structure. The mesa structure further preferably includes an overall width that is greater than the overall width than the active region of the DML that provides the MQW.