Mode-Locked Laser Nested Cavities Phase Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current mode-locked lasers face challenges in generating ultra-low phase noise optical and RF outputs, requiring separate CW lasers, high finesse etalons, and f-2f interferometers, which lead to large RF spurs and limitations in filtering, stability, and scalability.
Innovation Solution
A mode-locked laser with nested resonant cavities and a three-bandwidth Pound-Drever-Hall frequency stabilizer assembly, featuring optical fiber-based and periodic frequency filter cavities, allows independent control of center frequency and repetition rate, reducing phase noise through optical frequency division and eliminating the need for separate CW lasers and f-2f interferometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional mode-locked lasers use separate CW lasers, high finesse etalons, and f-2f interferometers for frequency stabilization, then frequency stability is improved, but device complexity increases and RF spurs are generated
Solution Approach 1:
The patent combines the frequency stabilization function directly into the mode-locked laser cavity by integrating a frequency-selective element (such as a Fabry-Perot etalon or ring resonator) within the laser cavity itself. This merging eliminates the need for separate CW lasers, external etalons, and f-2f interferometers, thereby reducing device complexity while maintaining frequency stability through the integrated frequency-selective mechanism
Solution Approach 2:
The frequency-selective element is nested within the mode-locked laser cavity structure, creating a hierarchical integration where the frequency stabilization component is embedded inside the main laser system. This nesting allows the frequency control function to be contained within the existing cavity architecture, reducing the need for external components and minimizing RF spur generation
2Ease of operation
If conventional mode-locked lasers use RF filtering to control repetition rate, then repetition rate control is achieved, but phase noise increases and filtering capabilities are limited
Solution Approach 1:
The patent replaces the conventional RF filtering approach (electrical/mechanical system) with an optical frequency-selective mechanism integrated into the laser cavity. The frequency-selective element directly controls the repetition rate through optical feedback, eliminating the need for external RF filtering and associated phase noise issues. This substitution provides cleaner phase noise characteristics while maintaining ease of repetition rate control
Solution Approach 2:
The integrated frequency-selective element provides inherent optical feedback within the laser cavity that automatically stabilizes the repetition rate. This feedback mechanism operates at the optical frequency level, providing more precise control with lower phase noise compared to external RF filtering. The feedback loop is embedded in the cavity design, allowing real-time adjustment and stabilization of the repetition rate
3Adaptability or versatility
If mode-locked lasers use nested cavity architecture with frequency-selective elements, then independent control of center frequency and repetition rate is achieved, but device complexity increases
Solution Approach 1:
The frequency-selective element integrated in the nested cavity architecture serves multiple functions simultaneously: it controls the center frequency of the optical output, stabilizes the repetition rate, and provides frequency comb line spacing control. This multi-functionality allows independent control of center frequency and repetition rate while avoiding the need for separate control mechanisms, thereby reducing overall device complexity despite the enhanced adaptability
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 achieves ultra-low phase noise RF outputs with reduced spurs, enhanced stability, and scalability, enabling a compact, portable, and efficient frequency comb source with independent control of center frequency and repetition rate.
Implementation Method 1
a three bandwidth Pound-Drever-Hall (PDH) frequency stabilizer assembly that includes at least three different optical bandpass filters
Implementation Method 2
Pound-Drever-Hall frequency stabilizer assembly
Implementation Method 3
nested resonant cavities including at least one optical fiber-based cavity and at least one periodic frequency filter cavity
Implementation Method 4
reducing phase noise through optical frequency division
Implementation Method 5
at least one periodic frequency filter cavity; FSRfilter/FSRfiber is an integer equal to or greater than 2
Implementation Method 6
optical fiber-based cavity characterized by a free spectral range, FSRfiber
Data Source
AI summary
A mode-locked laser (MLL) that produces ultra-low phase noise optical and RF outputs, includes two nested resonant optical cavities including an optical fiber-based cavity and an etalon, and a three bandwidth Pound-Drever-Hall (PDH) frequency stabilizer assembly incorporating three different optical bandpass filters. The optical fiber-based cavity is characterized by a free spectral range, FSRfiber, and the etalon is characterized by a free spectral range, FSRfilter, wherein FSRfilter/FSRfiber is an integer equal to or greater than 2. A method of generating ultra-low phase noise optical and RF outputs is disclosed. Optical and RF outputs have a phase noise that is less than −100 dBc/Hz at 1 Hz and less than −150 dBc at 10 KHz.