Dual Laser Phase-Locking for High Spectral Purity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for generating radio frequency (RF), millimeter-wave (mmW), and Terahertz (THz) signals using optical mixing of two lasers suffer from limited frequency and phase stability, resulting in inadequate spectral purity due to the instability of individual lasers, particularly when using DFB lasers, which makes it difficult to narrow the line-width below 1 MHz.
Innovation Solution
The implementation of a phase-locking mechanism using second-order nonlinear optical phenomena, specifically the Pockels effect, to electro-optically modulate and seed laser beams, ensuring mutual coherence and stability even when operating at different wavelengths, thereby improving the line-width and phase stability of the generated signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two independent lasers are used for optical mixing, then high frequency signals can be generated, but the line-width cannot be reduced below 1 MHz due to laser instability
Solution Approach 1:
The patent implements a feedback mechanism where the optical mixing signal is fed back to control the laser frequencies. The photodetector detects the mixing signal, and the resulting electrical signal is used to adjust the laser frequencies via current modulation, creating a closed-loop system that stabilizes the output frequency and reduces line-width.
Solution Approach 2:
The patent merges the functions of frequency generation and frequency stabilization into a single system. By combining the optical mixing process with feedback control using the same laser sources, the system achieves both high frequency generation capability and improved spectral purity without requiring separate stabilization systems.
2Reliability
If laser seeding is used to produce coherent beams, then phase stability improves, but frequency separation cannot be achieved because seeding produces beams of the same wavelength
Solution Approach 1:
The patent employs dynamic frequency tuning of the laser sources while maintaining phase coherence through feedback control. The laser frequencies are continuously adjusted to achieve the desired frequency separation for the mixing signal, while the feedback loop maintains the phase relationship between the beams, enabling both frequency versatility and phase stability.
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 significantly narrower line-width and superior phase stability for the generated signals, enabling the production of high spectral-purity RF, mmW, and THz signals without the need for an external seed signal, with the ability to tune frequencies over a wide range and distribute signals through optical fibers.
Implementation Method 1
The mixing may be performed with a nonlinear device such as a high-speed photodetector (PD)
Implementation Method 2
a scheme is applied based on a second order nonlinear phenomena, i.e., the linear electro-optic effect or Pockels effect
Data Source
AI summary
Signal generating systems and methods are described. One signal generation system includes first and second lasers configured to generate first and second laser beams having respective frequencies wherein a difference in the respective frequencies corresponds to an output frequency, a photodetector configured to produce a signal at the output frequency, and first and second electro-optic modulators configured to respectively electro-optically modulate the first and second laser beams using the signal to produce respective first and second modulated optical signals, each of the first and second modulated optical signals having a respective sideband corresponding to the frequency of the other one of the first and second laser beams. The first laser is seeded with the respective sideband of the second modulated optical signal and the second laser is seeded with the respective sideband of the first modulated optical signal to phase-lock the first and second laser beams to each other.