Determining strain components in a diamond waveguide from zero-field optically detected magnetic resonance spectra of negatively charged nitrogen-vacancy-center ensembles

Laser-written optical waveguides in diamonds are a key technology to enhance coupling between defect centers and light, boosting applications in nanoscale sensing and quantum information processing. However, laser writing of photonic structures produces strain in the diamond lattice, modifying the properties of defect centers in poorly understood ways. This study demonstrates that optically detected magnetic resonance spectroscopy provides sufficient information to fully characterize the spatial distribution of strain in such a device, even without a constant magnetic field. The work yields an accessible tool that could be very useful for advancing diamond-based quantum technologies.