The researchers of the Department report that plasmonic properties of a scanning tunneling microscope (STM) junction can be manipulated by nanofabrication of Au tips using focused ion beam (FIB) milling. An exemplary Fabry–Pérot like resonator of surface plasmons is demonstrated by producing a single groove on a smoothed tip shaft. STM-induced luminescence spectra of these tips exhibit spectral modulation originating from the interference between localized and propagating surface plasmon modes. In addition, the researchers show that the quality factor of the plasmonic Fabry–Pérot interference can be improved by optimizing the overall tip shape. This approach paves the way for near-field imaging and spectroscopy with a high degree of accuracy.