The tight spatial confinement of coherent light–matter interactions is a key prerequisite for scaling quantum technologies — for instance, to increase the storage density of optical quantum memories or to precisely address individual quantum emitters — but also shows promise for classical high-resolution microscopy. Normally, the achievable spatial resolution is limited by diffraction of the driving light fields.

In this work, we experimentally demonstrate two novel coherent approaches to overcoming the diffraction limit in a rare-earth ion-doped crystal. Using STIRAP and double STIRAP, optical excitations could be spatially confined down to 260 nm — well below the laser wavelength of 606 nm and close to the single-ion regime. Through tripod STIRAP, the coherence properties of the processes were improved and 2D excitation patterns with up to 41 individual excitation spots were prepared. As an alternative approach, novel broadband composite pulse sequences, which require only a single laser beam compared to other techniques, were developed and implemented. These achieved a reduction of the excitation width by 11% relative to conventional excitation with a single laser pulse. A systematic comparison of the techniques — including high-resolution methods such as STED, RESOLFT, and EIT — shows that STIRAP and composite pulses converge significantly faster toward smaller excitation regions.