Optical detection of magnetic resonance in nitrogen vacancy centre ensembles in bulk diamond using an off-resonant probe laser beam

Nitrogen vacancy (NV) centres are a type of defect in diamond that exhibit a number of interesting properties. NV centres can be optically excited around 450-650 nm and emit fluorescence at around 550-800 nm [1]. The optical excitation also spin polarises the negatively charged NV centres, permitting optical detection of magnetic resonance [2]. This allows nanotesla scale sensitive magnetometry to be performed with nanometre scale spatial resolution [3]. Generally, fluorescence based detection is used in magnetometric applications where photons are emitted in all directions thus making collection difficult. By utilising stimulated emission, the photons could be predominantly channelled into a single mode, thus greatly simplifying collection. This is especially important as the magnetometric sensitivity is proportional to the number of collected photons [3].