Dielectric Laterally Coupled DFB Grating for Deterministic Coupling
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Solution Overview
Problem
Traditional DFB laser manufacturing methods face challenges in adjusting wavelength and interval, introducing defects, and achieving precise control over grating coupling coefficient due to etching complexities and material limitations, leading to reduced performance and increased defects.
Innovation Solution
A DFB laser manufacturing method using a dielectric laterally coupled grating with a deterministic grating coupling coefficient, involving photolithography, dry etching, and deposition of insulating and high refractive index films to create a waveguide structure with precise geometry and grating design, enabling accurate control of grating coupling coefficient and minimizing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional epitaxial regrowth method is used to manufacture DFB laser, then the grating can be prepared near the active region, but the wavelength and interval cannot be adjusted freely and defects are introduced reducing performance
Solution Approach 1:
The patent extracts the grating structure from the traditional epitaxial regrowth process and implements it as a separate laterally coupled grating fabricated alongside the ridge waveguide. This separation allows independent optimization of the grating parameters for wavelength adjustment while avoiding defects introduced by regrowth processes, thus resolving the contradiction between adaptability and reliability
Solution Approach 2:
The patent introduces a laterally coupled grating as an intermediary structure that provides feedback to the laser mode without requiring direct integration with the active region through epitaxial regrowth. This intermediary approach enables wavelength tuning while maintaining laser performance by avoiding the harmful effects of regrowth-induced defects
2Ease of manufacture
If one-step reactive ion etching is used to fabricate LC gratings, then the grating can be formed during waveguide etching, but etching depth control is difficult due to footing and RIE-lag effects
Solution Approach 1:
The patent segments the grating fabrication process into multiple steps with different etching conditions. By dividing the single etching process into multiple stages, each with optimized parameters, the method achieves both ease of manufacture and precise etching depth control, overcoming the footing and RIE-lag effects that plague one-step etching
Solution Approach 2:
The patent applies preliminary actions by pre-defining the grating geometry and etching parameters before the actual etching process. This includes preparing the ridge waveguide with specific dimensions and using protective layers to prevent over-etching, thereby ensuring precise depth control while maintaining manufacturing simplicity
3Ease of manufacture
If metal grating is used for LC grating preparation, then the grating can be formed by vaporizing and peeling metal, but the peeling process is challenging for fine gratings and metal absorbs light increasing threshold
Solution Approach 1:
The patent replaces the metal grating with a dielectric or semiconductor material grating that can be fabricated using standard semiconductor processing techniques. This substitution eliminates the light absorption problem of metal gratings, reducing the laser threshold and increasing output power, while maintaining ease of manufacture through conventional fabrication processes
Solution Approach 2:
The patent employs composite material structures for the grating, combining materials with appropriate optical and mechanical properties. This allows the grating to be formed without metal peeling processes while minimizing light absorption, thus improving laser performance without sacrificing manufacturing ease
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 method enhances flexibility and accuracy in DFB laser design, reduces defects, and allows for high repeatability and multi-wavelength capabilities, improving the performance and cost-effectiveness of semiconductor laser manufacturing.
Implementation Method 1
performing photolithography on an epitaxial substrate of the laser without an etch-stop layer to obtain a photoresist pattern with a waveguide morphology
Implementation Method 2
performing dry etching and removing the photoresist to obtain a substrate of a waveguide structure
Data Source
AI summary
The present invention discloses DFB laser manufacturing method based on dielectric laterally coupled grating with deterministic grating coupling coefficient, comprising: S1: performing photolithography on an epitaxial substrate of the laser without an etch-stop layer to obtain a photoresist pattern with a waveguide morphology in a predetermined geometric configuration, and then performing dry etching and removing the photoresist to obtain a substrate of a waveguide structure in the predetermined geometric configuration; S2: depositing a layer of an insulating film with a low refractive index on the substrate; S3: depositing a dielectric film with a high refractive index on the insulating film; S4: performing photolithography on the dielectric film to prepare a photoresist pattern as a laterally coupled grating morphology; S5: performing etching and removing the photoresist for the dielectric film on the photoresist pattern to prepare a dielectric laterally coupled grating for the laser, and to further prepare a DFB laser.