Cascaded Hybrid DFB Laser Array for Tunable Multi-Wavelength Output
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Solution Overview
Problem
Current silicon photonic WDM laser sources are expensive and lack flexibility, with commercially available DFB lasers providing only single wavelength outputs, making it difficult to implement multi-wavelength DFB laser arrays due to phase errors and grating period precision issues, and existing alternatives like quantum-dot-based comb lasers lack sufficient power and flexibility for tunable wavelength switching.
Innovation Solution
A cascaded array of hybrid distributed feedback (DFB) lasers is formed by locating III-V gain material over a silicon waveguide with phase-shifted sampled Bragg gratings, allowing for both comb and tunable wavelength operations, with redundancy provided by silicon optical switches to ensure reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional DFB laser arrays are used to provide multi-wavelength output, then wavelength diversity is improved, but manufacturing precision deteriorates due to face-induced phase errors and grating period precision issues
Solution Approach 1:
The patent divides the laser array into independently controllable DFB laser sections, each with its own Bragg grating. This segmentation allows each section to be optimized and controlled separately, reducing the impact of manufacturing errors on the overall system while maintaining multi-wavelength capability.
Solution Approach 2:
The patent implements dynamic wavelength tuning by allowing individual DFB laser sections to be selectively activated or deactivated. This dynamic control enables the system to adapt to different wavelength requirements without being constrained by fixed manufacturing tolerances, as the operational wavelength can be changed by switching between sections.
2Adaptability or versatility
If quantum-dot-based comb lasers are used to achieve tunable wavelengths, then wavelength flexibility is improved, but power output deteriorates
Solution Approach 1:
The patent uses composite material structures combining quantum-dot gain media with distributed feedback Bragg gratings. This composite approach leverages the wavelength flexibility of quantum dots while the Bragg grating structure provides the necessary feedback and mode selection to achieve sufficient power output at the desired wavelengths.
Solution Approach 2:
The patent replaces traditional mechanical tuning mechanisms with optical feedback through Bragg gratings. The grating structure provides wavelength selection through optical interference rather than mechanical adjustment, enabling flexible wavelength tuning while maintaining high power output through efficient optical feedback.
3Ease of manufacture
If a cascaded array of hybrid DFB lasers is implemented, then manufacturing cost is reduced, but device complexity increases
Solution Approach 1:
The patent merges multiple DFB laser sections into a single cascaded array structure that can be fabricated using standard semiconductor processes. By combining the sections in a unified device architecture, the patent reduces overall manufacturing cost while managing complexity through systematic design of the cascaded structure.
Solution Approach 2:
The patent designs the cascaded DFB laser array to serve multiple functions: it can operate as a multi-wavelength source, a tunable laser, or a comb source depending on which sections are activated. This multi-functionality reduces the need for separate devices for different applications, thereby reducing overall manufacturing cost despite the increased complexity of individual device structure.
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 approach enables a low-cost, tunable multi-wavelength laser source with accurate channel spacing and fast wavelength tuning, overcoming the limitations of existing technologies by using phase-shifted sampled Bragg gratings and hybrid III-V/Si integration, facilitating efficient and scalable optical interconnects.
Implementation Method 1
a section of III-V gain material includes an active region that generates light
Implementation Method 2
This Bragg grating has a resonance frequency within a gain bandwidth of the section of III-V material and is transparent to frequencies that differ from the resonance frequency
Data Source
AI summary
The disclosed embodiments provide a laser source comprising a silicon waveguide formed in a silicon layer, and a cascaded array of hybrid distributed feedback (DFB) lasers formed by locating sections of III-V gain material over the silicon waveguide. Each DFB laser in the cascaded array comprises a section of III-V gain material located over the silicon waveguide, wherein the section of III-V gain material includes an active region that generates light, and a Bragg grating located between the III-V gain material and the silicon waveguide. This Bragg grating has a resonance frequency within a gain bandwidth of the section of III-V material and is transparent to frequencies that differ from the resonance frequency. Moreover, each DFB laser has a hybrid mode that resides partially in the III-V gain material and partially in silicon.