Sampled-Grating DFB Laser Assembly for Short-Cavity Wavelength Tuning
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Solution Overview
Problem
Current broadband tunable lasers, such as external cavity tunable lasers and Vernier effect based DBR lasers, cannot be directly modulated at high-speed due to their long cavities, and multiple wavelength DFB or DBR laser arrays require complex fabrication and low yield.
Innovation Solution
A distributed feedback semiconductor laser assembly with a short cavity is developed, featuring a grating layer with sampled gratings and independent electrode sections for high-speed direct modulation, allowing for wavelength tuning through the Vernier effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external cavity tunable lasers or Vernier effect based DBR lasers are used to achieve broadband wavelength tuning, then wavelength tuning range is improved, but cavity length increases causing inability for high-speed direct modulation
Solution Approach 1:
The patent transitions from a conventional lateral grating structure to a vertical grating structure, changing the spatial dimension of the grating orientation. This vertical configuration allows the grating to be stacked above the active region, significantly reducing the lateral cavity length while maintaining the wavelength tuning capability through the Vernier effect, thereby enabling high-speed direct modulation.
Solution Approach 2:
The patent implements a nested structure where the grating layer is positioned vertically above the active region layer, with the ridge waveguide confining both optically and electrically. This nested arrangement integrates the tuning function within the lasing cavity, reducing the overall device footprint and cavity length while preserving broadband tuning capability.
2Speed
If multiple wavelength DFB or DBR laser arrays are used to achieve broadband tuning with direct modulation, then high-speed modulation is improved, but fabrication complexity increases and yield decreases
Solution Approach 1:
The patent divides the grating layer into multiple discrete grating sections with different grating periods, each corresponding to a specific wavelength channel. These segmented gratings are electrically independent and can be individually controlled, enabling wavelength selection and broadband tuning within a single laser structure, avoiding the need for complex multi-laser array fabrication.
Solution Approach 2:
The patent creates a universal laser structure that can operate at multiple wavelengths through the vertical grating configuration. The single laser cavity with multiple grating sections can be tuned across a broad spectrum, making it a multi-functional device that replaces multiple specialized lasers, thereby simplifying fabrication and improving yield while maintaining high-speed modulation capability.
3Adaptability or versatility
If multiple wavelength DFB or DBR laser arrays are used with beam combiners or wavelength division multiplexers, then broadband output is improved, but device complexity and component requirements increase
Solution Approach 1:
The patent merges the wavelength tuning function and the light emission function into a single integrated laser structure. The vertical grating sections are directly integrated with the active region and ridge waveguide, eliminating the need for separate beam combiners or wavelength division multiplexers. This consolidation achieves broadband output capability while reducing overall device complexity.
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 laser assembly achieves high-speed direct modulation with a reduced cavity length, enabling continuous tuning over a broad wavelength range while maintaining high modulation bandwidth.
Implementation Method 1
a grating layer integrated between the spacer layer and the ridge, the grating layer including a plurality of sampled gratings along the longitudinal direction
Implementation Method 2
an active region layer disposed on a second side surface of the substrate... a second electrode layer electrically coupled to the first electrode layer, the second electrode layer including independent electrode sections
Implementation Method 3
a spacer layer disposed on the active region layer... the spacer layer is a p-type doped spacer layer extending between the active region layer and the grating layer
Data Source
AI summary
A distributed feedback (DFB) semiconductor laser assembly is disclosed. The DFB laser assembly includes a substrate extending along a longitudinal direction, a first electrode layer disposed on a first side surface thereof, an active region layer disposed on a second side surface thereof opposite the first side surface, and a spacer layer disposed on the active region layer. A ridge extends away from the active region layer and along the longitudinal direction. The DFB laser assembly also includes a grating layer integrated between the active region layer and the ridge, the grating layer including a plurality of sampled gratings along the longitudinal direction, and a second electrode layer electrically coupled to the first electrode layer, the second electrode layer comprising independent electrode sections disposed on the top ridge surface and each ridge side surface.