# Dresden 2017 – wissenschaftliches Programm

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# DF: Fachverband Dielektrische Festkörper

## DF 9: Poster Session

### DF 9.4: Poster

### Dienstag, 21. März 2017, 14:00–16:00, P1C

**A field-theoretical approach to light propagation and lasing in disordered photonic media** — •Zhong Yuan Lai, Oleg Zaitsev, and Johann Kroha — Physikalisches Institut, Universität Bonn, Germany

Random lasing is a phenomena which has continuously received attention since its
experimental discovery in 2000. We study the propagation of light in
an optically active, nonlinear and dielectrically disordered medium using a
functional integral formalism, which enables the derivation of an effective
low-energy
action, known as the Keldysh nonlinear sigma model [1]. In addition, we were
able to calculate explicit
transport quantities in the form of counting statistics [2] which we
could show, in the case of nonactive media, to be quantitatively the same as
previous diagrammatical calculations. Finally we study random lasing by
including the full matter-light interacting picture and integrating out the
matter fields, thus exposing the nonlinear nature of
effective photonic interactions in our theory. By obtaining the full interacting
saddlepoint of the nonlinear sigma model and systematically taking into account
fluctuations around the saddlepoint we obtain the diffusive modes. In this
manner we are able to obtain the photonic density correlation function with a
correlation length which we intepret as the average lasing spot size, and the
single-particle Green’s function which yields information about the average
laser linewidth.

[1] Lai, Z. Y. and Zaitsev, O., Phys. Rev. A **85**, 043838 (2012).

[2] Lai, Z. Y. and Zaitsev, O., Phys. Rev. A **88**, 023861 (2013)