Optical Switching of $\ddot{I}{‡}^{(2)}$ in Diamond Photonics

Abstract

Diamond's unique physical properties make it a versatile material for a wide range of nonlinear and quantum photonic technologies. However, unlocking diamond's full potential as a nonlinear photonic material with non-zero second-order susceptibility $\ddot{I}{‡}^{(2)}\ne 0$ requires symmetry breaking. In this work, we use a nanoscale cavity to demonstrate second-harmonic generation (SHG) in diamond, and demonstrate, for the first time, that the magnitude of the diamond's effective $\ddot{I}{‡}^{(2)}$ strongly depends on the electronic configuration of defects in the diamond crystal, such as nitrogen-vacancy centres. The modification of $\ddot{I}{‡}^{(2)}$ arises from photoionisation from the negative to neutral charge-state, and is manifested by quenching of SHG upon green illumination. Toggling the green illumination allows for optical switching of the device's $\ddot{I}{‡}^{(2)}$. Optical control of $\ddot{I}{‡}^{(2)}$ by defect engineering opens the door for second-order nonlinear processes in diamond.

8 pages, 4 figures