Static refractive index engineering of a singlewalled carbon nanotube through co-doping: A theoretical study

This paper presents a theoretical study of pristine single walled carbon nanotube (SWCNT) and SWCNT co- doped with combinations of Aluminum (Al), Phosphorous (P) and Nitrogen (N) along with their dielectric function spectra and calculated refractive indices. Dielectric function spectra of a pristine SWCNT and the SWCNT co-doped with Aluminum (Al) & Phosphorus (P) and another one co-doped with Al, P and Nitrogen (N) have been calculated using density functional theory implemented through the Cambridge sequential total energy package (CASTEP). The spectra show the variation of real and imaginary part of the dielectric function with frequency of the incident light. Polarized and unpolarized light as well as light through polycrystalline media has been considered. The value of static refractive index has been calculated using these curves. A substantial increase in the value of the static refractive index is observed when a pristine SWCNT is co-doped with Al and P but if in addition N atom is also introduced, a reduction in the value of static refractive index is observed though it does not fall lower than that of the pristine SWCNT. Thus, we propose that co-doping with atoms of different combinations of elements can be used as a novel and effective tool to manipulate the dielectric function and refractive index of SWCNTs and can pave the way to effective designing of various sensitive optical devices using SWCNTs for a variety of technological applications.