title: Effect of intrinsic surface roughness on the efficiency of intermodal phase matching in silica optical nanofibers.
abstract: We investigate the effect of intrinsic surface roughness associated to frozen thermal oscillations from the fiber fabrication process on the efficiency of third-harmonic generation via intermodal phase matching in silica nanofibers. Already a periodic wave with roughness of 0.2 nm reduces the efficiency by roughly 50% in a 1-mm optical nanofiber, with the divergence growing quadratically with distance. The surface wave period does not exhibit a large impact on the efficiency, due to averaging effects. However, both the location of the surface waves with respect to the phase matching radius as well as the surface wave amplitude have substantial effect on the efficiency, with the former presenting the possibility of transferring the power back to the pump wavelength. Simulations with a realistic superposition of random surface waves indicate that the conversion efficiency increases only for a few mm of propagation and reaches a maximum of less than 1%.
authors.forename: Muhammad I M Abdul
authors.initials: MI
authors.lastname: Khudus
authors.forename: Timothy
authors.initials: T
authors.lastname: Lee
authors.forename: Peter
authors.initials: P
authors.lastname: Horak
authors.forename: Gilberto
authors.initials: G
authors.lastname: Brambilla