Tunable Semiconductor Laser with Grounded Passive Section
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Solution Overview
Problem
Monolithically integrated semiconductor lasers with tunable distributed Bragg reflectors face challenges in achieving narrow linewidths due to the requirement for short laser cavities, which results in significant linewidths dominated by photon population and round trip time, affecting side mode suppression and transmission stability.
Innovation Solution
Incorporating a grounded passive section with no grating and electrical tracking on the optical waveguide, and using a common earth electrode to reduce electrical interference and linewidth/phase noise, while maintaining tunable reflection spectra through distributed Bragg reflector sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If narrow electrical isolation regions are provided between control electrodes to reduce electrical interference, then electrical isolation is improved, but the laser cavity length cannot be sufficiently extended to reduce linewidth
Solution Approach 1:
The introduction of a dedicated passive section creates a distinct segment专门 for electrical isolation, separating this function from the narrow isolation regions between electrodes. This allows the passive section to provide extensive electrical isolation (effectively increasing the isolation region length) without compromising the optical cavity design, as the passive section does not contain gratings and thus does not disrupt the optical mode.
Solution Approach 2:
The passive section serves as an intermediary structure that provides comprehensive electrical isolation between control electrodes while remaining optically transparent. It acts as a buffer zone that electrically isolates adjacent functional sections without introducing optical losses or disrupting the resonant cavity, thereby enabling both good electrical isolation and appropriate optical cavity length.
2Adaptability or versatility
If lengthy tunable distributed Bragg reflector sections are provided to achieve wide wavelength tuning, then wavelength tunability is improved, but laser cavity length increases resulting in more closely spaced longitudinal modes
Solution Approach 1:
The DBR sections are segmented into multiple sub-sections with different grating periods, allowing independent control of different wavelength ranges. This segmentation enables wide overall wavelength tuning by switching between different DBR sub-sections while keeping each individual section relatively short, thus maintaining adequate longitudinal mode spacing.
Solution Approach 2:
The DBR sections are made dynamically tunable through electrical control of the grating refractive index, allowing the reflection spectrum to be shifted across wide wavelength ranges. This dynamic tuning capability provides wide wavelength coverage without requiring physically lengthy static gratings, as the same physical structure can be electronically reconfigured to different wavelengths.
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 solution effectively reduces linewidth/phase noise and enhances side mode suppression, enabling stable transmission on a single longitudinal mode with improved discrimination between dominant and side modes.
Implementation Method 1
The DBRs are provided by gratings within the optical waveguide of the laser, and are tuned to control the lasing wavelength of the laser cavity
Implementation Method 2
lasers that are widely wavelength tunable have found favour with network providers
Data Source
AI summary
A monolithically integrated, tunable semiconductor laser with an optical waveguide, comprising a laser chip having epitaxial layers on a substrate and having first and second reflectors bounding an optical gain section and a passive section, wherein at least one of the reflectors is a distributed Bragg reflector section comprising a grating and configured to have a tunable reflection spectrum, wherein the laser is provided with a common earth electrode, wherein control electrodes are provided on the optical waveguide in at least the optical gain section and the at least one distributed Bragg reflector section, wherein the passive section is provided with an electrode or electrical tracking on the optical waveguide, the passive section is configured not to be drivable by an electrical control signal, and no grating is present within the passive section.