Two-Kappa DBR Laser for High-Speed Modulation
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Solution Overview
Problem
Conventional DBR lasers face challenges in achieving simultaneous good side-mode suppression ratio (SMSR) and high-speed operation, particularly in high-temperature environments, due to their uniform grating design.
Innovation Solution
The two-kappa DBR laser design incorporates a Fabry-Perot cavity with a high reflection mirror, a first DBR section, and a second DBR section, each with different kappa values, positioned to align the lasing mode with the long wavelength edge of the DBR reflection peak, enhancing longitudinal confinement and bandwidth through the detuned-loading effect and photon-photon resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform grating design is used in conventional DBR lasers, then the device structure is simple and easy to manufacture, but the side-mode suppression ratio (SMSR) and high-speed operation performance cannot be achieved simultaneously, especially in high-temperature environments
Solution Approach 1:
The DBR grating is divided into two distinct sections: a first DBR section with a first kappa value (κ1) and a second DBR section with a second kappa value (κ2), where κ2 < κ1. This segmentation allows each section to perform different functions - the first section provides strong reflection for high SMSR, while the second section enables high-speed modulation through reduced reactive photon penetration, resolving the contradiction between SMSR and high-speed performance.
Solution Approach 2:
Different kappa values are assigned to different spatial locations within the DBR structure. The first DBR section near the active region has a higher kappa value for strong confinement and high SMSR, while the second DBR section farther away has a lower kappa value to reduce reactive photon penetration and enable high-speed operation. This local differentiation resolves the performance trade-off.
2Reliability
If the lasing mode is aligned with the peak of the DBR reflection peak, then the SMSR is maximized, but the bandwidth and modulation speed are limited
Solution Approach 1:
The laser operates in a dynamic regime where the lasing mode is positioned at the long wavelength edge of the DBR reflection peak rather than at the peak center. This dynamic positioning exploits the slope of the reflection edge to achieve both high SMSR through the detuned-loading effect and high modulation bandwidth through reduced reactive photon effects, resolving the contradiction between SMSR and bandwidth.
3Reliability
If a single DBR section with high kappa is used, then the SMSR is improved, but the penetration depth of reactive photons increases, limiting the modulation speed
Solution Approach 1:
The DBR structure is segmented into two sections with different kappa values. The first DBR section has high kappa for strong reflection and high SMSR, while the second DBR section has low kappa to minimize reactive photon penetration depth. This segmentation allows the system to achieve both high SMSR and high modulation speed by distributing different functions to different sections.
Solution Approach 2:
The kappa parameter is changed across the DBR structure - the first section uses a high kappa value (κ1) for strong confinement, while the second section uses a lower kappa value (κ2) for reduced reactive photon effects. This parameter variation resolves the contradiction between SMSR and modulation speed by optimizing each section for its specific function.
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 improves the speed and bandwidth of the DBR laser, achieving high SMSR and shallow penetration of reactive photons, thereby enabling high-speed modulation and improved temperature performance.
Implementation Method 1
The first DBR section includes a first DBR grating with a length L1 in a range from 10 micrometers to 30 micrometers and a first kappa κ1. κ1L1 is in a range from 0.5 to 1.0.
Implementation Method 2
The second DBR section includes a second DBR grating with a second kappa κ2 that is less than the first kappa κ1 of the first DBR section.
Implementation Method 3
a Fabry-Perot (FP) cavity that includes a high reflection (HR) mirror, a first DBR section, and an active section. The active section is positioned between the HR mirror and the first DBR section.
Data Source
AI summary
A two-kappa DBR laser includes an active section, a HR mirror, a first DBR section, and a second DBR section. The HR mirror is coupled to a rear of the active section. The first DBR section is coupled to a front of the active section, the first DBR section having a first DBR grating with a first kappa κ1. The second DBR section is coupled to a front of the first DBR section such that the first DBR section is positioned between the active section and the second DBR section. The second DBR section has a second DBR grating with a second kappa κ2 less than the first kappa κ1. The two-kappa DBR laser is configured to operate in a lasing mode and has a DBR reflection profile that includes a DBR reflection peak. The lasing mode is aligned to a long wavelength edge of the DBR reflection peak.