Silicon and silicon nitride cylindrical microresonators made of optical fibers with sputter deposition

A cylindrical microresonator based on standard silica optical fibers is a promising platform for nonlinear devices such as low-repetition rate frequency comb generators. Though, enlarged mode volumes lead to higher pump powers and third-order nonlinearity level together with the stricter requirements on low propagation losses in order to achieve effective four-wave nonlinear interactions. We consider sputter deposition of thin films with higher nonlinear refractive index made of silicon and silicon nitride layers to enhance the nonlinearity within the microcavity. We inspect the variations of the cylinder radius that arise during the deposition and determine the quality factors achievable.