In the last five years, the group has developed an intense activity on optomechanics, the overlapping field of research between phononics and photonics. We demonstrated the potential of a new type of nanobeams to explore the coupling between the electromagnetic field in the 100s of THz frequency range and the mechanical vibrations in the GHz range. In this new type of nanostructures, we make profit of optical nonlinearities of the material used to fabricate these structures, silicon. The interaction between these optical nonlinearities and the optomechanical coupling in the MHz frequency range reveals a rich dynamical phase-space that can be used to control the complex dynamics of the structure, with expected impact in phononic circuits and secure data transmission. These promising results encourage us to face our current challenges. Our goals for the near future are basically to explore fabrication alternatives in order to push these complex dynamics to higher frequencies (GHz) and to analyse the robustness of these structure again fabrication imperfections. In addition, we are exploring other types of planar geometries to integrate more complex optomechanical architectures.

Cavity optomechanics is a relatively new field that has developed at an extremely rapid pace during the last decade, generating several breakthrough works every year. In our group we are mostly interested in room temperature operation of cavity optomechanic devices.  Among the great variety of optomechanical cavities, we are focusing our research on Si-based optomechanical crystals (OMC), which are probably one of the most interesting proposals in terms of technological implementation and optomechanic performances.

​

The ongoing research can be roughly summarized in three:

• High-frequency phonon sources. Those will certainly be one of the building-blocks required by a phononic-based information technology. We have recently demonstrated a novel pumping mechanism, based on the triggering of a self-pulsing limit-cycle within an OMC, that enables reaching the lasing regime with much lower requirements for the optical  and mechanical modes involved than those needed by the standard methods, i.e., dynamical back-action or phononic-molecule lasers. This ability to efficiently achieve self-sustained oscillation with no need for feedback electronics makes our OMC compelling for on-chip applications such as microwave clocks, in which CW light is fuelling the oscillation. Moreover, the dynamics of the non-linear system composed by the self-pulsing and the mechanical oscillators is incredibly rich, leading to more complex features, namely hysteresis, period doubling and chaos.

 

• High resolution thermal maps. Optomechanical crystals can display highly localized mechanical modes whose eigenfrequencies are sensible to the local environment. A pump and probe technique using two infrared tunable lasers has been implemented to locally heat (pump) and test the local temperature (probe) by quantifying the mechanical eigenfrequencies displacement.
   

• Disordered optomechanical crystals. Our structures are based on unitary cells displaying full-bandgaps both in the optical and in the mechanical dispersion bands. This feature enables the comparison of highly localized modes (optical and mechanical) close to the band edges when geometrical disorder is introduced on the optomechanical cystal (Anderson localization). Enhanced optomechanical coupling rates are expected in comparison with standard optomechanical crystal cavities.