The efficient manipulation of graphene's saturable absorption in resonant structures potentially allows for the demonstration of advanced all-optical components for modulation, switching and routing applications. The key idea towards this objective is that a strong pump wave reduces the losses experienced by a weak probe signal as it interacts with graphene. This is a recently demonstrated phenomenon in graphene, referred to also as cross saturable absorption (X-SA), in analogy to cross-phase modulation in multichannel systems dominated by Kerr nonlinearity. X-SA is an almost instantaneous nonlinear effect limited by the electron recombination time in graphene, in most cases in the sub-picosecond time scale. Thus, X-SA in graphene is an important candidate for the realization of advanced functionalities with low-power requirements and ultra-fast response.

A possible implementation of such an all-optical nonlinear element is shown in Fig. 1. A graphene monolayer uniformly covers a silica-cladded silicon disk traveling-wave resonator in an add-drop filter configuration. The operating principle of such a device lies in the selective fulfillment of the critical-coupling condition to efficiently route a low-intensity input signal either to the through or to the drop port. This is achieved by manipulating graphene losses using a second stimulus (the strong pump wave), introduced on demand (modulation/switching actions), or following a predefined pattern (routing). This functionality is demonstrated in Fig. 2, where an input pulse is efficiently routed between the through and the drop ports in the absence (presence) of a strong control pulse.


[J.1] Christopoulos T., Ataloglou V. G., and Kriezis Em. E., "All-optical nanophotonic resonant element for switching and routing applications exploiting graphene saturable absorption", Journal of Applied Physics127 (22), 223102, (2020). [pdf]

[J.8] Nousios G., Christopoulos T., Tsilipakos O., and Kriezis Em. E., "Dynamic Routing through Saturable Absorption in Graphene Photonic Resonators: Impact of Carrier Diffusion and Finite Relaxation Time", Journal of Applied Physics, 131 (5), 053104, (2022). [pdf]

Silicon Disk Covered with Graphene in an Add-Drop Configuration 

Fig. 1: Silicon-based add-drop filter for modulation, switching, and routing applications, induced by cross saturable absorption on the overlaying graphene monolayer.
(Click on image to enlarge)


Silicon Disk Covered with Graphene in an Add-Drop Configuration 

Fig. 2: Typical routing scheme: An input pulse is routed between the through and the drop ports in the absence/presence of a strong control pulse.
(Click on image to enlarge)



Powered by Joomla!. Valid XHTML and CSS.