Mode-Locked Laser Multi-Comb Generation via Intracavity Etalon
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Solution Overview
Problem
Existing methods for generating optical frequency combs with wider tooth spacing, such as using Fabry-Perot cavities, face challenges like reduced average power, cavity dispersion leading to unequal spacing, and complex stabilization requirements, limiting their accuracy and practicality for applications like atomic measurements and astronomy.
Innovation Solution
Inserting an intracavity Fabry-Perot etalon into a mode-locked laser cavity, allowing for control of tickmarks through etalon spacing, tilt angle, and gain adjustments, enabling flexible and accurate generation of high-frequency combs without requiring ultra-short laser cavities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a Fabry-Perot cavity is used to increase tooth spacing, then the spacing between frequency comb lines is increased, but the average power is reduced
Solution Approach 1:
The patent divides the frequency comb generation into two independent combs: a master comb from the mode-locked laser and a slave comb from the Fabry-Perot cavity. Each comb operates independently with its own characteristics, allowing the master comb to maintain high power while the slave comb provides the desired wide spacing. The two combs are then combined to achieve the final frequency comb with both wide spacing and high power.
Solution Approach 2:
The patent introduces a beam combiner as an intermediary device to merge the output of the master mode-locked laser and the slave Fabry-Perot cavity. This intermediary component allows the two independent frequency combs to coexist and combine their advantages: the master comb's high power and the slave comb's wide spacing, without direct interference between them.
2Length of moving object
If a Fabry-Perot cavity is used to increase tooth spacing, then the spacing between frequency comb lines is increased, but the spacing becomes unequal due to cavity dispersion
Solution Approach 1:
The patent segments the frequency comb function between two independent systems: the master mode-locked laser maintains equal spacing through its inherent mode-locking mechanism, while the slave Fabry-Perot cavity provides the spacing multiplication. By keeping these functions separate rather than relying on a single cavity, the equal spacing property is preserved from the master comb while achieving wide spacing through the combination.
Solution Approach 2:
The patent changes the operational parameters of the Fabry-Perot cavity by operating it in a regime where it acts as a pulse picker rather than a traditional resonant cavity. By controlling the cavity length and mirror reflectivity parameters, the system achieves integer multiplication of the repetition rate while maintaining the equal spacing characteristic from the master laser's mode structure.
3Length of moving object
If a Fabry-Perot cavity is used to increase tooth spacing, then the spacing between frequency comb lines is increased, but complex stabilization methods are required
Solution Approach 1:
The patent separates the stabilization requirements into two independent systems: the master mode-locked laser can be stabilized using standard techniques, and the slave Fabry-Perot cavity operates as a simple pulse picker with fixed parameters. This segmentation eliminates the need for complex coupled stabilization that would be required if a single cavity tried to perform both functions simultaneously.
Solution Approach 2:
The beam combiner acts as an intermediary that simplifies the overall system by allowing independent stabilization of the master and slave combs. Rather than requiring the Fabry-Perot cavity to be precisely stabilized to maintain both spacing and power, the intermediary combination approach allows each component to be optimized and stabilized independently, reducing overall system complexity.
4Productivity
If a low reflectivity interface is inserted inside a mode-locked laser cavity to multiplex repetition rate, then the repetition rate is multiplied, but the alignment is extremely critical and position must be exact
Solution Approach 1:
The patent extracts the repetition rate multiplication function from the main mode-locked laser cavity by using a separate slave Fabry-Perot cavity. Instead of inserting a critical low reflectivity interface into the master cavity, the multiplication function is taken out and performed independently in the slave cavity, which then feeds its output into the master comb through the beam combiner. This extraction eliminates the alignment sensitivity from the main laser system.
Solution Approach 2:
The beam combiner serves as an intermediary that allows the slave cavity's multiplied repetition rate to be integrated with the master laser without requiring precise alignment between them. The intermediary combines the two beams in a way that is tolerant of alignment variations, eliminating the need for the extremely critical alignment that would be required if the low reflectivity interface were inserted directly into the mode-locked laser cavity.
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 allows for the generation of high-frequency combs with enhanced accuracy and flexibility, achieving wider spacing and maintaining absolute precision, while avoiding the limitations of passive cavities and complex stabilization methods.
Implementation Method 1
Inserting an intracavity Fabry-Perot etalon into a mode-locked laser cavity
Implementation Method 2
A mode-locked laser produces a stream of identical pulses, which can have a duration of only several femtoseconds
Data Source
AI summary
Apparatus, systems, and methods of generating multi combs can be used in a variety of applications. In various embodiments, an etalon can be disposed in the laser cavity of a mode-locked laser to adjust frequency combs. Additional apparatus, systems, and methods are disclosed.