Tunable Laser Linewidth Narrowing via Dual-Mirror Optical Feedback
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Solution Overview
Problem
Current methods for narrowing the linewidth of tunable lasers, such as thermal tuning, are costly and complex, and existing optical feedback approaches are not cost-effective for achieving the necessary linewidth for high-speed coherent communications.
Innovation Solution
Injecting optical feedback into both cavity mirrors of a tunable laser, removing the optical isolator, and using reflection elements to generate feedback, which reduces the laser linewidth from 2 MHz to 5 kHz, enabling next-generation high-speed communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal tuning is used to narrow the laser linewidth, then the laser wavelength can be tuned by heating the optical waveguide, but the cost becomes prohibitive
Solution Approach 1:
The patent applies optical feedback by injecting a portion of the laser output back into the laser cavity through both cavity mirrors. This feedback mechanism stabilizes the laser mode and narrows the linewidth without requiring expensive thermal tuning components, thereby resolving the contradiction between achieving narrow linewidth and maintaining cost-effectiveness
Solution Approach 2:
The patent introduces an optical feedback path as an intermediary mechanism between the laser output and the laser cavity. This intermediary feedback path enables linewidth narrowing through optical interference effects rather than direct thermal manipulation, avoiding the need for costly thermal tuning hardware
2Manufacturing precision
If conventional optical feedback approaches are used, then some linewidth reduction is achieved, but the complexity and cost increase
Solution Approach 1:
The patent merges the feedback injection paths by directing feedback into both cavity mirrors simultaneously through a unified feedback mechanism. This combining approach achieves effective linewidth narrowing while avoiding the complexity of multiple independent feedback systems, resolving the contradiction between linewidth reduction and system simplicity
Solution Approach 2:
The patent makes the feedback mechanism universal by having it act on both cavity mirrors simultaneously, allowing a single feedback path to serve multiple functions in stabilizing the laser mode. This multi-functional approach reduces overall system complexity while achieving the desired linewidth narrowing
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 significantly reduces the laser linewidth, achieving a factor of 200 reduction in linewidth, supporting higher order modulation formats and reducing manufacturing costs by eliminating the need for optical isolators.
Implementation Method 1
injecting an optical feedback into the first and second cavity mirrors simultaneously
Implementation Method 2
The term 'a single mode laser' used herein shall mean that the light is emitted in one longitudinal cavity mode at a single frequency
Data Source
AI summary
A method or apparatus for narrowing the linewidth of a single mode laser is provided. The linewidth of a single mode laser is narrowed by injecting an optical feedback simultaneously into the first laser cavity mirror and the second laser cavity mirror of the single mode laser.