GaN Coupled Waveguide Lasers With N-Cladding DFB Gratings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fabrication of GaN-based DFB lasers is challenging due to difficulties in electrical activation of buried p-type layers, sensitivity of p-type GaN to point defects, and high p-type contact resistance, leading to increased forward voltage and optical losses, especially when etching DFB gratings into p-type layers.
Innovation Solution
The method involves transferring gallium and nitrogen-containing epitaxial layers from their original substrate to a carrier wafer, inverting the epitaxial stack to expose n-type cladding layers, and etching DFB gratings into the n-cladding region, which reduces the impact on conductivity and resistance, and using dielectric layers for optical coupling to provide efficient optical elements at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DFB gratings are etched into p-type GaN layers, then optical feedback is achieved for narrow lasing spectrum, but p-type GaN becomes resistive and contact resistance increases
Solution Approach 1:
The patent inverts the conventional approach by etching DFB gratings into n-type cladding layers instead of p-type contact layers. This inversion allows the grating structure to be formed in a layer that is less sensitive to point defects and does not compromise the electrical contact performance, thereby achieving narrow lasing spectrum without increasing contact resistance
Solution Approach 2:
The patent extracts the DFB grating function from the p-type contact layer and relocates it to the n-type cladding layer. This separation allows the p-type contact layer to maintain its electrical function while the n-type layer provides the optical feedback mechanism through the etched grating structure
2Measurement precision
If large fraction of p-type contact layer is removed to form grating, then optical feedback is improved, but forward voltage increases
Solution Approach 1:
Instead of removing material from the p-type contact layer to create the grating, the patent inverts the approach by forming the grating in the n-type cladding layer. This preserves the integrity and low resistance of the p-type contact layer, thereby maintaining lower forward voltage operation while still achieving the desired optical feedback
3Measurement precision
If regrown DFB gratings are used, then optical index contrast is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the grating formation process from the complex regrowth sequence and integrates it into the standard etching workflow. By forming gratings in the n-type cladding layer through conventional etching techniques, the need for additional regrowth steps is eliminated, reducing manufacturing complexity while maintaining sufficient optical index contrast
Solution Approach 2:
Instead of using regrowth to create contrasting index layers, the patent uses the existing n-type cladding layer structure and modifies it through etching. This approach copies the successful simple etching process from p-type layer fabrication and adapts it for grating formation, avoiding the complexity of regrowth 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 approach enables the production of high-performance laser diodes with reduced optical losses and lower forward voltage, while also offering a cost-effective method for manufacturing devices suitable for various applications including lighting, communication, and sensing systems.
Implementation Method 1
transferring gallium and nitrogen-containing epitaxial layers from their original substrate to a carrier wafer
Implementation Method 2
etching DFB gratings into the n-cladding region
Implementation Method 3
using dielectric layers for optical coupling to provide efficient optical elements
Data Source
AI summary
The present disclosure provides optical devices and methods for forming the optical devices. In some embodiments, the optical devices include active and passive regions. The active regions may include gallium and nitrogen containing epitaxial material, and the passive regions may include waveguide structures. The active and passive regions may be arranged on a carrier wafer in an end-to-end configuration. In other embodiments, the optical devices include laser devices or gain regions and dielectric waveguides. The laser devices or gain regions may include gallium and nitrogen containing epitaxial material.