Whispering-Gallery Dual-Frequency Comb Coupling With Polarized Modes
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Solution Overview
Problem
Current frequency comb technologies are limited in their ability to generate dual-frequency combs with stable repetition rates, which hinders applications such as two-way time transfer, coherent anti-Stokes Raman spectro-imaging, and highly sensitive range-finding, as they struggle to efficiently couple and phase-match radially-polarized and axially-polarized modes for effective spectroscopic analysis.
Innovation Solution
A whispering-gallery-mode resonator system is employed, utilizing x-cut lithium niobate and a toroidal loop-gap microwave resonator to support axially-polarized and radially-polarized modes with different free spectral ranges, where microwave fields couple light to create frequency combs by exploiting the nonlinearity and phase-matching properties of the resonator, allowing for the generation of dual-frequency combs with improved coupling and reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional frequency comb technologies are used, then basic frequency measurement is achieved, but the ability to generate dual-frequency combs with stable repetition rates is limited
Solution Approach 1:
The patent segments the optical modes into two distinct polarization groups (radially-polarized and axially-polarized modes) within the whispering-gallery-mode resonator. Each polarization group generates a separate frequency comb with its own repetition rate, enabling dual-frequency comb operation. The microring resonator is effectively divided into two independent mode families that can be independently controlled and phase-matched to different microwave frequencies.
2Measurement precision
If radially-polarized and axially-polarized modes are coupled without phase-matching, then mode coupling occurs, but effective spectroscopic analysis cannot be performed
Solution Approach 1:
The patent changes the microwave frequency parameter to match the free spectral range (FSR) of each polarization mode family. By tuning the microwave frequency to equal the FSR for radially-polarized modes and separately for axially-polarized modes, the system achieves phase-matching conditions that enable effective coupling and spectroscopic analysis. This parameter adjustment resolves the phase-matching requirement by aligning the microwave drive frequency with the resonator's modal structure.
3Adaptability or versatility
If a single frequency comb is generated, then simple frequency measurement is achieved, but applications requiring dual combs (two-way time transfer, coherent anti-Stokes Raman spectro-imaging, range-finding) cannot be implemented
Solution Approach 1:
The whispering-gallery-mode resonator is designed to simultaneously support multiple functions: generating two distinct frequency combs with different repetition rates, maintaining stable operation, and enabling various applications including two-way time transfer, coherent anti-Stokes Raman spectro-imaging, and range-finding. The single resonator structure performs the work of multiple separate comb generators while maintaining reliability through its inherent modal 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
The system effectively generates dual-frequency combs with reduced phase noise, enabling precise spectroscopic analysis and range-finding capabilities by orthogonally polarized mode separation and efficient coupling, enhancing the stability and accuracy of frequency measurements.
Implementation Method 1
Light in a radially-polarized mode mixes with a first microwave field to populate other radially-polarized spatial modes, and light in an axially-polarized mode mixes with a second microwave field to populate other axially-polarized spatial modes
Implementation Method 2
microwave fields couple light to create frequency combs by exploiting the nonlinearity and phase-matching properties of the resonator
Data Source
AI summary
Techniques dual-frequency comb sources are disclosed. In the illustrative embodiment, a whispering-gallery-mode resonator supports a family of radially-polarized modes and a family of axially-polarized modes. A laser excites one radially-polarized mode and one axial-polarized mode. A microwave field is applied at a free spectral range for each family of modes, coupling the radially-polarized and axially-polarized mode excited by the laser with other modes in the family, creating a dual-frequency comb in the resonator.