Electromagnetically induced transparency in a diamond spin ensemble enables all-optical electromagnetic field sensing
V. M. Acosta, K. Jensen, C. Santori, D. Budker, and R. G. Beausoleil
Accepted
We use electromagnetically-induced transparency (EIT) to probe the narrow electron-spin resonance of nitrogen-vacancy centers in diamond. Working with a multi-pass diamond chip at temperatures $6\mbox{-}30~{\rm K}$, the zero-phonon absorption line ($637~{\rm nm}$) exhibits an optical depth of $6$ and inhomogenous linewidth of ${\sim}30~{\rm GHz}$ full-width-at-half-maximum (FWHM). Simultaneous optical excitation at two frequencies separated by the ground-state zero-field splitting ($2.88~{\rm GHz}$), reveals EIT resonances with a contrast exceeding $6\%$ and FWHM down to $0.4~{\rm MHz}$. The resonances provide an all-optical probe of external electric and magnetic fields with a projected photon-shot-noise-limited sensitivity of $0.2~{\rm V/cm/\sqrt{Hz}}$ and $0.1~{\rm nT/\sqrt{Hz}}$, respectively. Operation of a prototype diamond-EIT magnetometer measures a noise floor of ${\lesssim}1~{\rm nT/\sqrt{Hz}}$ for frequencies above $10~{\rm Hz}$ and Allan deviation of $1.3{\pm}1.1~{\rm nT}$ for $100~{\rm s}$ intervals. The results demonstrate the potential of diamond-EIT devices for applications ranging from quantum-optical memory to precision measurement and tests of fundamental physics.