Ultrasmall high efficency all-optical switch with single silicon nanoparticle

In this study, we found giant photothermal nonlinearity with 𝑛2 = 10-1𝜇𝑚2/𝑚𝑊 in ~100𝑛𝑚 silicon nanoblocks, based on Mie-resonance enhanced absorption and efficient temperature increase via thermal insulation. Through a continuouswave pump-probe setup, we demonstrated an ultrasmall high-contrast all-optical switch with 90% modulation depth. Due to the 0.001𝜇𝑚3 small geometrical size, thermal dissipation is as fast as nanosecond, leading to modulation speed at GHz, which is much faster than other thermal optic switches. The large and fast all-optical switching could open the possibility toward high-density integrated photonic nanocircuits based entirely on silicon.