On-chip all-optical switch, possessing the unique ability of switching signal light propagating in any incident waveguide channel into any required output waveguide channel, is one of the core components of all-optical networks, and ultrahigh-speed and ultrawide-band information processing chips. For practical chip-integration applications, several significant indexes, i.e. on-chip trigger, ultrafast response, ultralow energy consumption, high switching efficiency between different waveguide channels, and wideband (or multiple-wavelength) operation, are stringently required. The basic realization mechanism of all-optical switching is based on the third-order nonlinear optical Kerr effect, i.e. the control-light induced refractive index changes. owing to relatively small third-order optical nonlinearity of conventional semiconductors and organic polymers, it is very difficult to realize a large-scale integration of on-chip-triggered all-optical switch only appealing to traditional silicon photonics or organic photonics alone. On the other hand, owing to serious ohmic losses of metal and accordingly severe propagation losses of surface plasmon polaritons (SPPs) in the near-infrared range, it is infeasible to construct a large-scale integrated plasmonic waveguide channel arrays for the all-optical switch application.

Gong’s group proposed a new compound enhancement of nonlinearity method, and a novel plasmonic-photonic hybrid nanostructure by combining the advantages of plasmonics and photonics. They obtained a multicomponent nanocomposite material nano-Au:(IR140:PDTP-DFBT) having very large third-order nonlinear optical susceptibility and ultrafast response of several picoseconds order simultaneously. On-chip plasmoni-induced transparency was achieved in the plasmonic-photonic hybrid nanocavity, which provides four operating wavelengths for the all-optical switch. Low-loss SiN slot waveguides were used as access waveguides to construct a chip-integrated 2×2all-optical switch device, switching units of which was triggered by control waveguides in the upper layer in the term of evanescent field. The control light threshold power of the all-optical switch was reduced by four orders, the control light intensity reduced to 450 kW/cm2，and an ultrafast response time of 63 ps was maintained. Therefore, an ultrafast, ultralow-power, on-chip-triggered all-optical switch with multiple operating wavelengths was realized in integrated photonic circuits directly. This work was published in Advanced Optical Materials（Zhen Chai, Yu Zhu, Xiaoyong Hu, Xiaoyu Yang, Zibo Gong, Feifan Wang, Hong Yang, Qihuang Gong, “On-chip optical switch based on plasmon-photon hybrid nanostructure-coated multicomponent nanocomposite”, Advanced Optical Materials Vol.4, No. 8, 1159-1166 (2016)），and was selected as the cover article of the journal.

This work was highly evaluated by the journal of Advanced Optical Materials: “This paves a way to overcome the intrinsic material limitations for the realization of very-large-scale integrated photonic circuits and chips, and additionally provides a lab-on-chip platform for fundamental research of nonlinear optics and quantum optics”. This work was also highly evaluated by the Materials Views China of WILEY publishing group.

The work was supported by the National Basic Research Program of China, State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, and Collaborative Innovation Center of Extreme Optics.