Different Regimes of Ultrashort Pulse Propagation in Disordered Layered Media with Resonant Loss and Gain

Abstract

Different optical nanostructures containing both loss and gain components attract ever-increasing attention as novel advanced materials and building blocks for a variety of nanophotonic and plasmonic applications. Unique tunable optical signatures of the so-called active metamaterials support their utilization for sensing, imaging, and signal processing on micro-and nanoscales. However, this tunability requires flexible control over the metamaterial parameters, which could be provided by involving a set of nonlinear interactions. In this paper, a method of governing ultrashort pulses is proposed by varying the level of a population difference disorder in a random active metamaterial. This enables us to deliver three different interaction regimes: self-induced transparency (low disorder), localization regime (moderate disorder), and light amplification (strong disorder) corresponding to strongly different light pulse speeds. Since this control could be realized via rather plain tools, like simple pump tuning, the proposed disordered medium opens a room of opportunities for designing a peculiar active component for a whole set of highly demanded optical applications.

Controlling wave-front shape and propagation time with tunable disordered non-Hermitian multilayers

“…[20] or with the adaptive-pumping approach [58]. Note that the quadratic model of disorder (5) give essentially the same results as the linear one [52], but is more convenient for symmetric representation of gain and loss. The similar linear model was experimentally realized recently in the context of random lasing [59].…”

“…We use here the two-valued quadratic model of disorder described in Ref. [52]. In fact, we have the multilayer structure with the initial population difference in the jth layer of the medium corresponding to the distance ( j − 1)δ L < z ≤ jδ L given by w…”

“…The fronts are the monochromatic waveforms having finite switching time, the loss and gain are due to resonant media and not merely a phenomenological imaginary part of permittivity, and the disorder can be controlled with external pump and change in time due to gain depletion and loss saturation. We have previously reported the study of short pulse propagation and localization in such media [52] with the possibility to slow down or even stop the pulse. Here, we deal with the opposite case of continuous radiation with the emphasis on the transient process of steady-state establishment for the light intensities large enough to saturate the medium and give substantial transmission.…”