Dual-frequency optical source phase noise reduction
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Solution Overview
Problem
Current methods for generating dual optical-frequency signals and microwave sources face challenges in achieving enhanced difference-frequency stability and reduced phase noise, particularly due to reliance on sophisticated and costly devices like mode-locked frequency combs and absolute frequency references that are prone to technical noise.
Innovation Solution
The approach employs dual pump lasers to generate stimulated Brillouin oscillations at distinct wavelengths within a common resonator, utilizing a dual-frequency optical source with a Brillouin shift frequency and free spectral range that is an integer submultiple of the Brillouin shift frequency, enabling phase modulation and optical frequency division to achieve stable microwave signals without the need for mode-locked lasers, thus reducing phase noise and increasing frequency separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mode-locked frequency combs and absolute frequency references are used to generate dual optical-frequency signals, then frequency stability can be achieved, but device complexity and cost increase significantly
Solution Approach 1:
The patent extracts the essential function of frequency stabilization from complex mode-locked frequency comb systems by using a simplified dual-laser approach with a common optical resonator. Only the critical frequency reference function is retained while removing unnecessary complexity of full frequency comb generation systems.
Solution Approach 2:
The invention replaces expensive, complex absolute frequency references and mode-locked lasers with simpler, more cost-effective continuous-wave laser sources. The system uses commercially available lasers with stabilized frequencies rather than requiring sophisticated frequency comb generation equipment.
2Adaptability or versatility
If mode-locked frequency combs are used for microwave signal generation, then frequency coverage can be extended, but phase noise increases
Solution Approach 1:
The patent merges two separate laser frequency stabilization systems into a single common optical resonator system. By having both lasers reference the same resonator modes, the system achieves wide frequency coverage while the common reference suppresses phase noise through correlated fluctuations cancellation.
Solution Approach 2:
The common optical resonator acts as an intermediary that mediates between the two laser sources. It provides a shared frequency reference that enables both lasers to be stabilized simultaneously, achieving extended frequency coverage while maintaining low phase noise through the intermediary's stabilizing influence.
3Length of stationary object
If dual pump lasers are used to generate stimulated Brillouin oscillations, then frequency separation can be increased, but device complexity increases
Solution Approach 1:
The single optical resonator serves multiple functions: it provides frequency reference for both pump lasers, enables stimulated Brillouin scattering for frequency conversion, and establishes the frequency separation through its mode structure. This multi-functionality achieves large frequency separation without requiring multiple specialized devices.
Solution Approach 2:
The system exploits changes in the Brillouin shift parameter and resonator mode spacing to achieve large frequency separation. By tuning the pump laser frequencies to different resonator modes and utilizing the Brillouin scattering process, the system generates widely separated output frequencies from a single resonator structure.
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 method achieves significant phase noise reduction in microwave signals by increasing the division ratio, allowing for larger frequency separations and more robust reference stability, while using simpler and less costly optical components, thereby improving the stability and efficiency of microwave-frequency signal generation.
Implementation Method 1
first and second optical output signals of the dual-frequency optical reference source at respective first and second output frequencies v1=v pump1-vB and v2=v pump2-vB comprise stimulated Brillouin laser output generated by simultaneous optical pumping of the optical resonator
Data Source
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AI summary
A dual-frequency optical source comprises: (a) first and second pump laser sources arranged to generate optical pump power at respective first and second pump laser frequencies v pump1 and v pump2 ; and (b) an optical resonator characterized by a Brillouin shift frequency v B and a free spectral range that is substantially equal to an integer submultiple of the Brillouin shift frequency. Each one of the first and second pump laser sources is frequency-locked to a corresponding resonant optical mode of the optical resonator. First and second optical output signals of the dual-frequency optical reference source at respective first and second output frequencies v 1 =v pump1 -v B and v 2 =v pump2 -v B comprise stimulated Brillouin laser output generated by simultaneous optical pumping of the optical resonator by the first and second pump laser sources, respectively. An output difference frequency v 2-v 1 is greater than about 300 GHz.