All-optical dc nanotesla magnetometry using silicon vacancy fine structure in isotopically purified silicon carbide

Abstract

We uncover the fine structure of a silicon vacancy in isotopically purified silicon carbide (4H-28SiC) and reveal not yet considered terms in the spin Hamiltonian, originated from the trigonal pyramidal symmetry of this spin-3=2 color center. These terms give rise to additional spin transitions, which would be otherwise forbidden, and lead to a level anticrossing in an external magnetic field.We observe a sharp variation of the photoluminescence intensity in the vicinity of this level anticrossing, which can be used for a purely alloptical sensing of the magnetic field. We achieve dc magnetic field sensitivity better than 100 nT√Hz within a volume of 3 × 10-7mm3 at room temperature and demonstrate that this contactless method is robust at high temperatures up to at least 500 K. As our approach does not require application of radiofrequency fields, it is scalable to much larger volumes. For an optimized light-trapping waveguide of 3 mm3, the projection noise limit is below 100 √Hz.