title: Quantum coherence in an optical modulator.
abstract: Semiconductor quantum well electroabsorption modulators are widely used to modulate near-infrared (NIR) radiation at frequencies below 0.1 terahertz (THz). Here, the NIR absorption of undoped quantum wells was modulated by strong electric fields with frequencies between 1.5 and 3.9 THz. The THz field coupled two excited states (excitons) of the quantum wells, as manifested by a new THz frequency- and power-dependent NIR absorption line. Nonperturbative theory and experiment indicate that the THz field generated a coherent quantum superposition of an absorbing and a nonabsorbing exciton. This quantum coherence may yield new applications for quantum well modulators in optical communications.
authors.affiliation: Physics Department and Institute for Quantum and Complex Dynamics (iQCD), Broida Hall Building 572, Room 3410, University of California, Santa Barbara, CA 93106, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Carter
authors.forename: V
authors.initials: V
authors.lastname: Birkedal
authors.forename: C S
authors.initials: CS
authors.lastname: Wang
authors.forename: L A
authors.initials: LA
authors.lastname: Coldren
authors.forename: A V
authors.initials: AV
authors.lastname: Maslov
authors.forename: D S
authors.initials: DS
authors.lastname: Citrin
authors.forename: M S
authors.initials: MS
authors.lastname: Sherwin