Stark Shift Control of Single Optical Centers in Diamond

Lifetime-limited optical excitation lines of single nitrogen-vacancy (NV) defect centers in diamond have been observed at liquid helium temperature. They display unprecedented spectral stability over many seconds and excitation cycles. Spectral tuning of the spin-selective optical resonances was performed via the application of an external electric field (i.e., the Stark shift). A rich variety of Stark shifts were observed including linear as well as quadratic components. The ability to tune the excitation lines of single NV centers has potential applications in quantum information processing.

Figure 1

Energy level scheme of the NV center in diamond. The optically excited ${}^{3}E$ state is doubly degenerated. The inset shows the fluorescence intensity of a single defect as a function of an applied electric field. Points are measured values, and the solid curve is a guide to the eye.

Figure 2

Fluorescence excitation zero phonon line of single NV defect centers at $T=1.8\mathrm{K}$. (a),(b) Excitation line for a single defect in a diamond nanocrystal (type Ib). Spectra (a) and (b) have been recorded with and without deshelving 488 nm laser, respectively. (c) Excitation line in type IIa crystal. The excitation power was 5 nW, far below the saturation value of about 100 nW. The line shown in the inset is fitted with a Lorentzian profile and has a lifetime-limited homogeneous width of 13 MHz.

Figure 3

Spectral trails of different single defects found in the same laser spot. Excitation spectra have been recorded with stepwise changing of the applied field from 0 to $0.32\mathrm{MV}{\mathrm{m}}^{-1}$. Some excitation lines are observed only for a specific range of field values.

Figure 4

Examples for the Stark shift of three different defect centers. The local electric field was calculated from the externally applied bias using the Lorentz local field correction (for details see text). (a) Linear Stark effect with $\Delta \mu =1.3\mathrm{D}$. (b) Mostly quadratic Stark effect with $\Delta \mu =-37\mathrm{mD}$ and $\Delta \alpha =-3.5\times {10}^4{\AA }^3$. (c) Linear and quadratic Stark dependences, with $\Delta \mu =1.1\mathrm{D}$ and $\Delta \alpha =-5.4\times {10}^4{\AA }^3$.