All-Optical Switching of Localized Surface Plasmon Resonance with Phase Change Material for Intelligent Computing Applications

Toshiharu Saiki Department of Electronics and Electrical Engineering, Keio University, Yokohama, Kanagawa, Japan Takashi Hira Department of Electronics and Electrical Engineering, Keio University, Yokohama, Kanagawa, Japan Kenta Kuwamura Department of Electronics and Electrical Engineering, Keio University, Yokohama, Kanagawa, Japan Yuya Kihara Department of Electronics and Electrical Engineering, Keio University, Yokohama, Kanagawa, Japan Tasuku Yawatari Department of Electronics and Electrical Engineering, Keio University, Yokohama, Kanagawa, Japan Shohei Kanazawa Department of Electronics and Electrical Engineering, Keio University, Yokohama, Kanagawa, Japan Yusuke Hirukawa Department of Electronics and Electrical Engineering, Keio University, Yokohama, Kanagawa, Japan

Control of localized surface plasmon resonance (LSPR) excited on metal nanostructures has drawn attention for applications in dynamic switching of plasmonic devices. As a reversible active media for LSPR control, chalcogenide phase-change materials (PCMs) such as GeSbTe (GST) are promising for high-contrast robust plasmonic switching. We demonstrated the LSPR switching of individual Au nanospheres on a GST thin film by alternating irradiation by a femtosecond pulse laser for amorphization and a continuous wave laser for crystallization [1]. The metal-dielectric-metal nanosandwich structure is an effective approach for enhancing LSPR switching contrast. The LSPR peaks of the hybridized modes, particularly the magnetic dipole mode, shift dramatically with the refractive index of the dielectric material. Recently we obtained a large peak shift for the magnetic dipole mode in a single Au nanorod (NR)/GST/Au film sandwich structure [2].

Owing to the plasticity and the threshold behavior during both amorphization and crystallization of PCMs, PCM-based LSPR switching elements possess a dual functionality of memory and processing. Integration of LSPR switching elements so that they interact with each other will allow us to build non-von-Neumann computing devices. As a specific demonstration, we discuss the implementation of a cellular automata (CA) algorithm into interacting LSPR switching elements. In the model we propose, PCM cells, which can be in one of two states (amorphous and crystalline), interact with each other by being linked by a AuNR, whose LSPR peak wavelength is determined by the phase of PCM cells on the both sides. The CA program proceeds by irradiating with a light pulse train. The local rule set is defined by the temperature rise in the PCM cells induced by the LSPR of the AuNR, which is subject to the intensity and wavelength of the irradiating pulse

Figure 1: One-dimensional CA model of GeSbTe nanopads .

[1] T. Hira et al., Appl. Phys. Lett. 103, 241101 (2013).

[2] T. Hira et al., Appl. Phys. Lett., in press.

saiki@elec.keio.ac.jp