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Updated: Sep 11, 2025
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Microwave Photonics Systems Based on Whispering-gallery-mode Resonators
Published on: August 5, 2013
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Monitoring phase-matching of third harmonic generations in microbubble whispering gallery mode resonators by a
Optics Express
|August 13, 2025
Summary
Researchers precisely monitored third harmonic generation (THG) phase-matching in microbubble resonators (MBRs) using a novel opto-thermal method. This technique precisely determined the phase-matching wavelength, enabling efficient THG with low laser power.
Area of Science:
- Photonics and Optical Engineering
- Nonlinear Optics
- Materials Science
Background:
- High Q whispering gallery mode (WGM) optical resonators offer high nonlinear frequency conversion efficiency at low laser intensities.
- Third harmonic generation (THG) in WGM resonators necessitates precise phase-matching, typically achieved through careful dispersion engineering.
- Input laser power-induced thermal dispersion is often employed to fine-tune phase matching, but mode identification can be challenging in dense spectra like those in microbubble resonators (MBRs).
Purpose of the Study:
- To develop and apply a novel dynamic opto-thermal disruption method for monitoring temperature-dependent THG phase-matching conditions in MBRs.
- To precisely determine the modal phase-matching wavelength and characterize the THG conversion bandwidth.
- To achieve efficient THG with low pump power in high Q MBRs.
Main Methods:
- Utilized a novel dynamic opto-thermal disruption method to interrupt and monitor the thermal drift of fundamental resonance.
- Step-by-step monitoring of the temperature-dependent THG phase-matching condition in MBRs.
- Characterized the THG conversion bandwidth and efficiency at a specific wavelength.
Main Results:
- Precisely determined the modal phase-matching wavelength, finding it to be 22.6 pm offset from the cold cavity resonance.
- Measured a THG conversion bandwidth of 670 MHz at 517.7 nm.
- Achieved a peak THG conversion efficiency of 2.6×10-9 with a low pump power of 1.5 mW in a high Q (2.9×107) MBR.
Conclusions:
- The dynamic opto-thermal disruption method effectively enables precise monitoring of THG phase-matching in MBRs, even with dense resonant spectra.
- The study demonstrates efficient THG in MBRs with potential for bandwidth expansion through combined dispersion control methods.
- This work provides a valuable technique for characterizing and optimizing nonlinear frequency conversion in micro-resonators.
