Abstract
We review our recent studies on all-optical switching and memory operations based on thermo-optic and carrier-plasma nonlinearities both induced by two-photon absorption in silicon photonic crystal nanocavities. Owing to high-Q and small volume of these photonic crystal cavities, we have demonstrated that the switching power can be largely reduced. In addition, we demonstrate that the switching time is also reduced in nanocavity devices because of their short diffusion time. These features are important for all-optical nonlinear processing in silicon photonics technologies, since silicon is not an efficient optical nonlinear material. We discuss the effect of the carrier diffusion process in our devices, and demonstrate improvement in terms of the response speed by employing ion-implantation process. Finally, we show that coupled bistable devices lead to all-optical logic, such as flip-flop operation. These results indicate that a nanocavity-based photonic crystal platform on a silicon chip may be a promising candidate for future on-chip all-optical information processing in a largely integrated fashion.
Highlights
It used to be a great challenge to tightly confine light in a wavelength-scale volume, which had limited the capability of photonics technologies in various aspects
In this article, we focus on application to alloptical switching and memory operations based on optical nonlinear interaction
We investigate all-optical switching and memory action in silicon photonic crystal nanocavity devices
Summary
It used to be a great challenge to tightly confine light in a wavelength-scale volume, which had limited the capability of photonics technologies in various aspects. This particular cavity shows a theoretical Q of over 108 and an experimental Q of 1.3 million with a mode volume of 1.5(λ/n)3 [4, 7]. For this, we investigate alloptical operations based on carrier-induced nonlinearity and examine the features of photonic crystal nanocavities for such applications. As has been studied in various forms, all-optical switches can be realized using optical resonators, where a control optical pulse induces a resonance shift via optical nonlinear effects For such a resonator-based switch, there is a twofold enhancement in terms of the switching power if a small cavity with a high-Q is employed. We demonstrate bistable memory action employing basically the same nanocavity devices and present an example of design for on-chip all-optical logic circuits consisting of two bistable nanocavities
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