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Optical Switching of χ^{(2)} in Diamond Photonics
Sigurd Flågan1, Joe Itoi1, Prasoon K Shandilya1
1University of Calgary, Institute for Quantum Science and Technology, Calgary, Alberta T2N 1N4, Canada.
Physical Review Letters
|December 19, 2025
Summary
Researchers demonstrated optical switching of diamond
Area of Science:
- Nonlinear optics
- Quantum photonics
- Materials science
Background:
- Diamond possesses unique physical properties, making it suitable for nonlinear and quantum photonic technologies.
- Achieving a nonzero second-order nonlinear susceptibility (χ(2)) in diamond requires breaking its inherent symmetry.
- Defects, such as nitrogen-vacancy centers, influence diamond's optical properties.
Purpose of the Study:
- To demonstrate second-harmonic generation (SHG) in diamond using a nanoscale cavity.
- To investigate the dependence of diamond's effective χ(2) on the electronic configuration of defects.
- To show optical control over diamond's χ(2) for nonlinear photonic applications.
Main Methods:
- Fabrication of a nanoscale cavity to confine light within the diamond crystal.
- Measurement of second-harmonic generation (SHG) in diamond.
- Utilizing green illumination to induce photoionization and modify defect charge states, thereby altering χ(2).
Main Results:
- Successfully demonstrated SHG in diamond within a nanoscale cavity.
- Established a strong dependence of the effective χ(2) magnitude on defect electronic configurations, specifically nitrogen-vacancy centers.
- Observed photoionization-induced modification of χ(2), leading to SHG quenching upon green light exposure.
- Demonstrated optical switching of the device's χ(2) by toggling green illumination.
Conclusions:
- The effective second-order nonlinear susceptibility (χ(2)) in diamond is tunable via defect engineering.
- Photoionization of defects provides a mechanism for optical control of χ(2).
- This work enables optical switching of nonlinear properties in diamond, paving the way for advanced second-order nonlinear photonic devices.
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