Suspended Directly Modulated Laser for High-Bandwidth Confinement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The speed of directly modulated lasers (DMLs) is limited by the optical confinement factor to volume ratio, which restricts the interaction between gain and light, and existing configurations face challenges with thermal dissipation and reliability.
Innovation Solution
A DML structure with a waveguide spaced apart from a substrate by an air gap, using thin claddings and supports with high thermal conductivity to achieve strong optical confinement and improved thermal dissipation, while avoiding strain-related reliability issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If normal ridge or buried hetero structures are used, then the device structure is simple and easy to manufacture, but the optical confinement factor to volume ratio is limited by index contrast
Solution Approach 1:
The patent changes the refractive index parameter by introducing an air gap (n=1.0) between the waveguide and substrate, creating a high-contrast index environment that enhances optical confinement. This parameter change allows the optical confinement factor to exceed 100%, directly improving the modulation bandwidth and relaxation oscillation frequency while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
Solution Approach 2:
The patent adds a vertical dimension to the waveguide structure by suspending it above the substrate using an air gap, transforming it from a planar heterostructure to a three-dimensional suspended configuration. This dimensional change enables superior optical confinement in the vertical direction while maintaining lateral confinement, achieving enhanced light-gain interaction without compromising manufacturing ease.
2Speed
If thin claddings are used to enhance optical confinement, then the optical confinement factor increases, but thermal dissipation becomes challenging
Solution Approach 1:
The patent introduces supports as intermediary elements that couple the suspended waveguide to the substrate. These supports serve dual functions: they maintain the air gap for optical confinement while providing thermal conduction pathways from the thin claddings to the substrate, enabling effective heat dissipation despite the reduced cladding thickness.
Solution Approach 2:
The patent segments the thermal management function from the optical confinement function by using separate components: the air gap provides optical confinement while the supports provide thermal conduction. This segmentation allows thin claddings to achieve high optical confinement factor without compromising thermal dissipation, as heat can conduct through the supports to the substrate.
3Temperature
If the waveguide is suspended by supports, then thermal dissipation is improved, but the device complexity increases
Solution Approach 1:
The patent optimizes the support dimensions and spacing parameters to achieve effective thermal management with minimal structural complexity. By carefully selecting support thickness, width, and separation distance, the design achieves good thermal dissipation while maintaining a relatively simple suspended waveguide structure that can be fabricated using modified standard processes.
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 enhances the relaxation oscillation frequency and modulation bandwidth, enabling data rates of 200 Gb/s or higher and a 3-dB bandwidth of 150 GHz or more, while maintaining reliability.
Implementation Method 1
the ratio is limited by an index contrast between a semiconductor core multiple quantum well (MQW) material and surrounding cladding
Implementation Method 2
supports with high thermal conductivity to achieve strong optical confinement and improved thermal dissipation
Implementation Method 3
a distributed Bragg reflector (DBR) section
Data Source
AI summary
A laser includes a substrate, first and second claddings, a gain medium, and multiple supports. The first cladding is spaced apart from the substrate by an air gap. A thickness of the first cladding in a vertical direction is in a range from 0.05-0.15 micrometers. The gain medium is disposed on the first cladding opposite the air gap. The second cladding is disposed on the gain medium opposite the first cladding. A thickness of the second cladding in the vertical direction is in a range from 0.05-0.15 micrometers. The supports are coupled to each of the substrate, the first cladding, the gain medium, and the second cladding to retain the first cladding, the gain medium, and the second cladding spaced apart from the substrate.