All-optical control of the speed of light by molecular-aggregates nanofilms

Molecular aggregates were established as promising nanomaterials supporting very interesting optical phenomena in the past decade [1]. Among the all-optical devices, there has been a great interest in the optical engineering of the speed of light. So far, coherent population oscillations (CPO) is one of the most exploited mechanisms to obtain slow light since it deals with two-level systems and is insensitive to dephasing processes, which makes room temperature operation feasible [2].
In this work [3] we propose a new optical CPO-based device considering nanofilms of linear aggregates of dye molecules, so-called J-aggregates. We consider J-aggregates as modeled by an ensemble of inhomogeneously broadened two-level systems at low temperatures as in previous works [4]. The response of an ultrathin ?lm of oriented linear J-aggregates to a strong pump ?eld, and two sidebands slightly detuned with respect to the strong field is studied. Moreover, numerical integration of the equations allows us to analyze the slow-light performance of this device with pulsed input signals at Ghz-bandwidths.
We show that the cooperative behavior of these molecular assemblies leads to large fractional delays and low distortions of the input pulses, even for such short length scales. We also show how the already predicted optical bistability on J-aggregates [5], could be used to provide a fast all-optical switch between two well differentiated time delays and pulse distortions, while keeping the same background intensity.

References
[1] Jasper Knoester, Int. J. Photoenergy 2006, 61364 (2006).
[2]  Matthew S. Bigelow, Nick N. Lepeshkin, and Robert W.
Boyd, Phys. Rev. Lett. 90, 113903 (2003).
[3] E. Cabrera-Granado, E. Diaz and Oscar G. Calderon,
Phys. Rev. Lett. 107, 013901 (2011).
[4] V. A. Malyshev, H. Glaeske, and K. H. Fisher, "Intrinsic optical
bistablility of an ultrathin film consisting of oriented linear
aggregates, " J. Chem. Phys. 113, 1170 (2000).