Stimulated optomechanical excitation of surface acoustic waves in a microdevice

Abstract

stimulated Brillouin interaction between sound and light, known to be the strongest optical nonlinearity common to all amorphous and crystalline dielectrics, has been widely studied in fibres and bulk materials but rarely in optical microresonators. The possibility of experimentally extending this principle to excite mechanical resonances in photonic microsystems, for sensing and frequency reference applications, has remained largely unexplored. The challenge lies in the fact that microresonators inherently have large free spectral range, whereas the phase-matching considerations for the Brillouin process require optical modes of nearby frequencies but with different wave vectors. Here we rely on high-order transverse optical modes to relax this limitation and report the experimental excitation of mechanical resonances ranging from 49 to 1,400 mHz by using forward Brillouin scattering. These natural mechanical resonances are excited in ~100 µm silica microspheres, and are of a surface-acoustic whispering-gallery type.

Brillouin cavity optomechanics with microfluidic devices

“…in [9][10][11][12][13][21][22][23] . Specifically for the capillary geometry that we use here, it is indicated 24 that a wide variety of acoustic WGMs exist in the shell-type geometry.…”

“…As described in Fig. 2, the 'Brillouin' optomechanical process 13 allows for excitation and measurement of these acoustic WGM oscillations by coupling continuous-in-time light at an optical resonance, while interrogating the optomechanical oscillation at the fibre output of the system (see Methods). No modulation of the pump laser is needed.…”

“…1d,e) while supporting a considerable overlap between the optical and mechanical modes. The acoustic modes are optically excited by means of forward 10,12,13 and backward 9,11 SBS, that is, F-SBS and B-SBS, respectively.…”

“…Subsequently, the platforms for Brillouin scattering were extended from bulk materials and fibres, to droplets 6 , nanospheres 7 , photonic-crystal fibres 8 and crystalline resonators 9,10 . The recent demonstration of Brillouin scattering in microspheres 11 was followed by the Brillouin cooling 12 and excitation 10,13 of their vibrational modes as well; which indicates that Brillouin effects can serve as a general mechanism for actuating (and interrogating) vibration in various types of micromechanical resonators. In separate research on optofluidic devices 14,15 , the motion of liquids has been used to control light, but light has rarely been used to actuate a fluid 16 .…”

Cavity optomechanics on a microfluidic resonator with water and viscous liquids

“…5,6 Just like we use more than one sense (e.g., eyes and ears) to detect hazards, optomechanics might suggest a bridge between the seemingly parallel optical and mechanical detection fields. The recent availability of liquid containing bubble shaped resonators, 7,8 in combination with optomechanical vibrations at .GHz rate, [9][10][11][12] might pave the way for ultrasound investigations on analytes in liquids. Nevertheless, cavity optomechanics on non-solid phases of material was never before demonstrated.…”