Mechanical Tunability of an Ultranarrow Spectral Feature of a Rare-Earth-Doped Crystal via Uniaxial Stress

Rare-earth-doped crystals have numerous applications ranging from frequency metrology to quantum information processing. To fully benefit from their exceptional coherence properties, the effect of mechanical strain on the energy levels of the dopants---whether it is a resource or perturbation---needs to be considered. We demonstrate that by applying uniaxial stress to a rare-earth-doped crystal containing a spectral hole, we can shift the hole by a controlled amount that is larger than the width of the hole. We deduce the sensitivity of $\mathrm{Eu}$${}^{3+}$ ions in an $\mathrm{Y}$${}_{2}$$\mathrm{Si}\mathrm{O}$${}_{5}$ matrix as a function of the crystal site and the crystalline axis along which the stress is applied.