The Multi-Photon Induced Fano Effect

The ordinary Fano effect occurs in many-electron atoms and requires an auto-ionizing state.With such a state, photo-ionization may proceed via pathways that interfere, and the characteristicasymmetric resonance structures appear in the continuum. Here we demonstrate that Fano structure15may also be induced without need of auto-ionization, by dressing the continuum with an ordinarybound state in any atom by a coupling laser. Using multi-photon processes gives complete, ultra-fastcontrol over the interference. We show that a line-shape indexqnear unity (maximum asymmetry)may be produced in hydrogenic silicon donors with a relatively a weak beam. Since the Fanolineshape has both constructive and destructive interference, the laser control opens the possibility20of state-selective detection with enhancement on one side of resonance and invisibility on the other.We discuss a variety of atomic and molecular spectroscopies, and in the case of silicon donors weprovide a calculation for a qubit readout application