Forward stimulated Brillouin scattering (FSBS) is an acousto-optic interaction between co-propagating pump and Stokes fields through an acoustic wave. It can be enhanced greatly with the combination of electrostrictive force and radiation pressure in nanowire waveguides and hybrid waveguides. Hybrid phononic-photonic waveguides,which are studied for optical mode conversion and control of coherent information, are favorable to realize FSBS with flexible tunability of acoustic and optical modes. The compound-material device comprises two kinds of material and provides independent control of the optical and acoustic dispersion relationships. This separate control over the optical and acoustic modes improves the structural tunability.
In this paper, we present the generation of forward stimulated Brillouin scattering (FSBS) inhybrid phononic-photonic waveguides. To confine theoptical and acoustic waves simultaneously, a hybrid waveguide is designed by embedding the silicon line defect in the silicon nitride phononic crystal slab. Bytaking into account three kinds hybrid waveguide, the appropriate structural parameters are obtained to enhance the acousto-optic interaction.We fabricate the honeycomb hybrid waveguide with a CMOS compatible technology. The forward Brillouin frequency shift is measured up to 2.425 GHz and the acoustic Q-factor of the corresponding acoustic mode is 1100. The influences of pump power, acoustic loss, nonlinear optical loss andlatticeconstanton the acousto-optic interaction in FSBS are analyzed and discussed.The proposed approach has important potential applications in on-chip all-optical signal processing.
The paper is published on Optical Express (Vol. 24, Issue 12, 2016.doi: 10.1364/OE.24.013051). This work is supported by the National Natural Science Foundation of China under Grant No. 61377074.
Fig. 1 (a) Measured RF spectrum of MLM-EDFL before being injected into the hybrid waveguide. (b) Measured RF spectrum of MLM-EDFL after propagating through the hybrid waveguide without the pump. (c) Measured RF spectrum of the hybrid waveguide with the pump. (d) Zoomed-in RF spectrum at 2.42 GHz. The dot is the experimental value and the solid curve is the fitted.
