Coherent Excitation-Selective Spectroscopy of Multipole Resonances

Abstract

Thin films are central to modern technologies ranging from semiconductors to metamaterials. The authors observe that by placing a subwavelength thin film at the node of an electromagnetic standing wave, it is possible to separate electric from magnetic dipole terms, or dipole from quadrupole terms, in the absorption spectrum. The technique is twice as sensitive as conventional measurements, functions at very low laser power, and reveals resonances that are invisible to existing spectroscopies. This approach could see application in analytical chemistry, condensed matter physics, nanotechnology, and forensic science.