Pushing the limit of high-Q mode of a single dielectric nanocavity

High index dielectric nanostructure supports different types of resonant modes. However, it is very challenging to achieve high-Q factor in a single subwavelength nanoresonator due non-hermtian property the open system. Here, we present universal approach finding out series modes nonspherical nanocavity by exploring quasi-bound state continuum. Unlike conventional method relying on heavy computation (ie, frequency scanning FDTD), our built upon leaky mode engineering, through which many can be easily achieved constructing avoid-crossing (or crossing) eigenvalue for pair The Q-factor up 2.3*10^4 square nanowire (NW) (n=4), 64 times larger than highest (Q=360) reported so far nanodisk. Such attributed suppressed radiation corresponding eigenchannels and simultaneously quenched electric(magnetic) at momentum space. As proof concept, experimentally demonstrate emergence (Q=380) scattering spectrum silicon nanowire.