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Exploring random-lasing in structured optofluidic channel and randomly perforated GaAs membranes

Shivakiran Bhaktha

à 11h en salle C. Brot

Random lasing arises in mirrorless scattering active media when the multiple scattering process provides enough gain to overcome the losses. This field has gained popularity in recent years due to its unique properties and ease of fabrication. In this seminar I would like to present the experimental initiatives taken by our group in the past two years of my post-doctoral tenure, in trying to understand random lasing behaviour in various disordered systems. Firstly, the design of an innovative structured PDMS microfluidic channel that we filled with an ethanolic dye solution will be presented. We observed random laser emission attributed to the inherent randomness in this structure. The origin of random lasing, its dependency on pump laser parameters, and the effects of partial pumping will be discussed in the talk. Secondly, we demonstrate experimentally for the first time random lasing in the diffusive regime on a semiconductor membrane with a fully-random collection of holes. These results are obtained on patterns of subwavelength holes in a 2D Al0.2Ga0.8As membrane with embedded GaAs quantum wells suspended on a low index AlGaAs substrate. Laser operation has been achieved under pulsed optical pumping. Several random patterns were tested and both single-mode and multimode emissions were observed. Furthermore, recent results on studies of light transport within the perforated membranes as a function of wavelength will also be discussed.