Plasmon-enhanced ultrafast time-resolved spectroscopy of NV-containing diamond

We investigated ultrafast nonlinear optical effects in nitrogen-vacancy (NV)-containing diamond which is in contact with a gold-coated blazed diffraction grating using a pump-probe reflectivity technique. The reflectivity change caused by optical Kerr effect and two-photon absorption was enhanced several times because of the electric field enhancement induced by the propagating surface plasmon (PSP). Furthermore, by performing measurements with varying the incident angle of the pump beam and numerical simulations of the electric field using the Finite Difference Time Domain method, signal enhancement due to the PSP was confirmed both experimentally and theoretically. This study paves the way for applications based on enhanced nonlinear optical effects in diamond.