Friday, 5 October 2018 from 15:00 to 16:00 (Europe/Rome)
University of Rome, Sapienza
Aula Cortini Dipartimento di Fisica – Edificio E Fermi
Alexander V. Poshakinskiy
Ioffe Institute, St. Petersburg, Russia
In semiconductor quantum wells, photoelastic interaction is increased by several orders of magnitude at the exciton resonance frequency, making them promising for optomechanics . Under resonant laser pump, the exciton-mediated stimulated Raman scattering leads to controllable sound amplification or attenuation, akin to the optomechanical heating and cooling effects. At higher pump intensities, acoustic lasing can be realized . In case of simultaneously strong exciton–light and exciton–sound coupling, the eigen modes of the system are phonoritons, i.e., a hybrid of phonons, photons, and excitons. An additional degree of freedom that corresponds to the mode type can be regarded as an artificial “energy” dimension. Finite wave vector of the pump laser induces a synthetic magnetic field in the virtual “coordinate–energy” space, making the transport of light and sound non-reciprocal .
In particular, the sound transmission coefficient through an array of quantum wells under laser pump is strongly asymmetric. The system can amplify phonons transmitted from top to bottom of the structure while attenuating those transmitted from bottom to top, enabling construction of an acoustic diode. In planar microcavities with embedded quantum wells, where interacting light, sound, and excitons are simultaneously confined, the lateral transport non-reciprocity is induced when the system is excited by a beam that carries angular momentum, e.g., a Bessel beam of non-zero order. The system can be used to build a nanoscale acoustic circulator, a device that rotates the direction of sound propagation by a certain angle clockwise.
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 A.V. Poshakinskiy, A.N. Poddubny, and A. Fainstein, Phys. Rev. Lett. 117, 224302 (2016).
 A.V. Poshakinskiy and A.N. Poddubny, Phys. Rev. Lett. 118, 156801 (2017).