Two-laser spectral hole burning in a colour centre in diamond

Abstract Using two high-resolution lasers a short lived (∼1 ms) hole burning spectrum has been observed in the 637 nm zero-phonon transition associated with the nitrogen-vacancy centre in diamond. Amongst the prominent antiholes the ones at ±2.88 GHz coincide in frequency with that obtained in EPR for a spin-doublet-singlet splitting of a metastable 3 A state. In this work it is claimed that 3 A is the ground state and this is supported by the observation of temperature-dependent magnetic circular dichroism signals. Details in the hole burning spectrum are then interpreted in terms of a strain split 3 A→ 3 E transition.