Combining acoustic waves and optomechanical resonators could lead to a new generation of ultra-stable optomechanical oscillators with high-spectral purity and low phase noise signals directly at the frequency of interest. Moreover, this approach would allow an easy on-chip integration at μm scale, where the lack of good quality and miniaturized source is a severe issue. The resonator part of such a system will be made of a 1D photonic crystal nanobeam suspended over a silicon waveguide, sustaining optical modes around 1.55 μm and mechanical modes around a few GHz. On the other hand, Interdigital transducers (IDT) will provide acoustic waves in the GHz allowing a full mechanical control of the oscillating structure. In addition, phononic waveguides can be designed to engineer the acoustic velocity of the mechanical propagating modes in order to achieve the desired delay for a correct stabilization of the oscillations. The proposed system can be then exploited for potential on-board applications such as navigation and telecommunication systems, metrology or sensing. Design, simulation, fabrication and experimental results of resonant mechanical excitation in the GHz will be discussed, with particular emphasis on the time-domain studies of the propagating acoustic waves, where a specific time-gating technique is needed in order to properly extrapolate the delay information.
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