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Method for measuring the nonlinear index n2 in optical microresonators
Optics Letters
|July 31, 2026
Summary
This study introduces a straightforward method to measure the nonlinear refractive index (n2) in photonic devices. The technique compares resonant frequency shifts in microresonators, offering a definitive approach for integrated photonics.
Area of Science:
- Photonics
- Nonlinear Optics
- Materials Science
Background:
- The nonlinear refractive index (n2) is crucial for third-order nonlinear optical processes.
- Existing n2 measurement techniques are often complex or incompatible with fabricated photonic devices.
Purpose of the Study:
- To present a simple and definitive method for measuring n2 in integrated microresonators.
- To enable accurate characterization of nonlinear optical properties in on-chip photonic devices.
Main Methods:
- Comparing optically induced resonant frequency shifts of two modes within the same mode family in microresonators.
- Utilizing silicon nitride microring resonators with varying Si/N stoichiometries.
Main Results:
- Successfully determined the nonlinear refractive index (n2) using the proposed method.
- The experimental results for the third-order nonlinear susceptibility (χ(3)) and the linear susceptibility (χ(1)) align with Miller's rule.
Conclusions:
- The presented method offers a simple, definitive, and device-compatible approach for n2 characterization.
- This technique is valuable for the development and optimization of integrated photonic devices reliant on nonlinear optical effects.
