Analysis of modes in a free-standing nanowire cavity by FDTD simulation

The mode frequency and the quality factor of nanowire cavities are calculated for the intensity spectrum obtained by the finite-difference time-domain (FDTD) technique and the Padé approximation.In the free-standing nanowire cavity with the dielectric constant ε=6.0 and the length of 5 μm,the quality factors of 130,159,and 151 are obtained for modes with frequency around 798 THz,at the cavity radius of 60 nm,75 nm,and 90 nm,respectively.The obtained field distribution of the fundamental transverse mode shows that the mode field is confined very well by the nanowire cavity even when the radius of nanowire is much smaller than the mode wavelength.