The optical properties of the silicon naniwires (SiNWs) fabricated by a method of metal-assisted
electroless etching have been investigated. The optical parameters of both SiNWs and the Si wafer,
including dielectric function (ε (ω) ) and the effective refractive index ( N(ω) ), could be obtained from
the light-absorption theory and Kramers-Kronig relation. From the comparation of calculated
characteristics, we can observe that the refractive index of the SiNWs is reduced to 1.26 while that of
Si wafer is changing from 2.4 to 6.2 in the range of 1.5-4eV, and the imaginary part of complex
dielectric constant of Si NWs is about two orders of magnitude lower than that of Si wafer. There are
two peak positions in the curve of Si wafer, while just one broad peak position in that of Si NWs.
These differences could be considered as the reasons for the special characteristic of the Si NWs.