Conversion between surface acoustic waves and guided modes of a quasi-periodic structured nanobeam

The generation of acoustic waves in structured nanobeams containing optomechanic cavities is a topic of current interest. In this paper, we theoretically study the efficient conversion of surface acoustic waves (SAW) generated on a substrate by an RF electric signal into the acoustic waves of a nanobeam. First, we demonstrate the possibility of converting the SAW generated on a silicon substrate with a thin piezoelectric AlN layer into the guided mechanical modes of a straight nanobeam with a maximum efficiency of −22.6 dB. This can be achieved by using a set of inter-digitated transducers with radial fingers, which provide SAW focusing towards the nanobeam entrance. We analyse the nature of the modes created inside the nanobeam and the conversion efficiency of the SAW into the different modes. Then, we study the interaction of these waves with a one-dimensional phononic crystal nanobeam containing a cavity. The latter is constituted by an array of holes and stubs and has been proven in our recent works to be very efficient for optomechanic applications. We calculate the transmission properties of the cavity modes and discuss the efficiency of generating the cavity modes from the initial SAW.

[1]  Oskar Painter,et al.  Optical transduction and routing of microwave phonons in cavity-optomechanical circuits , 2016, Nature Photonics.

[2]  Martin Maldovan,et al.  Sound and heat revolutions in phononics , 2013, Nature.

[3]  Oskar Painter,et al.  Two-dimensional phononic-photonic band gap optomechanical crystal cavity. , 2014, Physical review letters.

[4]  Kartik Srinivasan,et al.  Coherent coupling between radiofrequency, optical and acoustic waves in piezo-optomechanical circuits , 2015, Nature Photonics.

[5]  Y. Pennec,et al.  Band gaps and cavity modes in dual phononic and photonic strip waveguides , 2011, AIP Advances.

[6]  B. Djafari-Rouhani,et al.  A one-dimensional optomechanical crystal with a complete phononic band gap , 2014, Nature Communications.

[7]  K. Hashimoto.  Surface Acoustic Wave Devices in Telecommunications , 2000 .

[8]  Optical modulation of coherent phonon emission in optomechanical cavities , 2018, APL Photonics.

[9]  Ken-ya Hashimoto,et al.  Surface Acoustic Wave Devices in Telecommunications: Modelling and Simulation , 2000 .

[10]  A. Vainsencher,et al.  Bi-directional conversion between microwave and optical frequencies in a piezoelectric optomechanical device , 2016 .

[11]  B. Djafari-Rouhani,et al.  Optomechanic interaction in a corrugated phoxonic nanobeam cavity , 2014 .

[12]  J. Vasseur,et al.  Simultaneous existence of phononic and photonic band gaps in periodic crystal slabs. , 2010, Optics express.

[13]  D. Bouwmeester,et al.  Dynamic modulation of photonic crystal nanocavities using gigahertz acoustic phonons , 2011, 1205.1346.

[14]  K. Vahala,et al.  Optomechanical crystals , 2009, Nature.