Photonic crystal all-optical switching is a very important mesoscopic photonic device, having great potential applications in fields of optical computing, optical interconnection networks, and ultrahigh-speed information processing systems. Low threshold pump power, ultrafast response time, and high switching efficiency are the crux of the practical applications of photonic crystal all-optical switching. Owing to the relatively small nonlinear optical coefficients of conventional materials in the optical communication range, the threshold pump power is very high, often in the order of GW/cm2. This has restricted the practical applications of photonic crystal all-optical switching.

Gong’s group proposed a new mechanism to construct photonic materials. They combine nonlinearity enhancement associated with Bragg resonance and strong quantum confinement effect to achieve a large nonlinear susceptibility. They fabricated an Au/LiNbO3 composite material based on this mechanism. The prototype device of photonic crystal all-optical switching is realized in the optical communication range. The threshold pump power is reduced by three orders of magnitude, the threshold pump intensity reduced from GW/cm2 order to 9 MW/cm2. An ultrafast response time of 24.2 ps is reached by use of the fast relaxation dynamics of nonequilibrium electrons in gold. A high switching efficiency of 80% is also reached. They also fabricated multi-component nanocomposite material, and realized low-power and ultrafast photonic crystal all-optical switching based on defect modes coupling.

These works can improve the process of practical applications of mesoscopic photonic devices including all-optical switching. This also provides a new approach for the study of nonlinear photonic materials.

The work was supported by the Creative Research Group Project of the National Natural Science Foundation of China, and the National Basic Research Program of China.