SUNRISE · Silicon Brillouin-assisted Optoelectronic Oscillator Based on Subwavelength Membranes

Silicon-based technologies offer tantalizing prospects for low-cost mass production of high-performance optoelectronic circuits by leveraging the maturity of complementary-metal-oxide semiconductor facilities. However, the processing and generation of high-quality radiofrequency signals using optoelectronic oscillators is still hampered by the spectral response of Si filters, which are unable to provide a rejection band on the order of MHz. Stimulated Brillouin scattering (SBS) has been at the core of recent stunning demonstrations of key on-chip functionalities for microwave photonics, exhibiting several properties that are ideally suited to overcome the limitation of Si photonic filters. SBS interactions can be orders of magnitude stronger in suspended Si waveguides compared to conventional optical fibers, but approaches demonstrated so far are mainly limited by trade-off between phonon lifetime and photon-phonon overlap.This project will address a completely new route to overcome the trade-off between long phonon lifetimes and large photon-phonon overlap in conventional Si optomechanical waveguides. The original idea is to exploit the unique degrees of freedom released by subwavelength Si nanostructuration to achieve flexible control of the shape and dispersion of optical and mechanical modes in order to maximize optomechanical coupling and Brillouin gain. This approach will be used to demonstrate a Si optoelectronic oscillator that exploits the intrinsic narrow linewidth of the Brillouin effect to achieve three orders of magnitude phase-noise reduction compared to the state of the art. The SUNRISE technology will open a whole new research domain in integrated optomechanics with great opportunities for fundamental and applied research. The unique expertise combination of the experienced researcher, the host institution and the two teams hosting secondments offers all the ingredients to significantly contribute to the next generation of microwave photonic systems