Nonlinear optical response of silica and hyybrid silica/silicon disc micro resonators

Micro resonators of different topologies are of interest due to their potential applications as components in future generations of optoelectronic circuits [1]. The high quality factors in combination with small mode volume allow resonators to collect high intensities at rather moderate levels of coupled light [2]. Raman scattering [3], parametric effects [4], and thermal nonlinearity [5] have been investigated both experimentally and theoretically. The thermal nonlinearity has lowest threshold and causes bistable behavior [6]. In this work a bistable operation of silica micro disc resonators and hybrid ones made of silica/silicon has been investigated experimentally. It has been found, that in a hybrid silica/silicon micro resonators a bistability effect has an opposite sign in comparison with a silica disc micro resonator. The bistable behavior of silica micro resonators [6] caused by a thermal nonlinearity exhibits transmission spectrum shift into a longer wavelength region. This corresponds to a positive numerical refractive index temperature derivative for silica. In our experiments a new type of disc micro resonators - hybrid silica/silicon ones - has been produced (see Fig. 1). It is clearly seen, that under a silica layer there is a layer of silicon, which has higher refractive index and thus the eigen mode of such structure tends to be concentrated inside the silicon layer.