Temporal Behavior of Radiation-Pressure-Induced Vibrations of an Optical Microcavity Phonon Mode

Abstract

We analyze experimentally and theoretically mechanical oscillation within an optical cavity stimulated by the pressure of circulating optical radiation. The resulting radio frequency cavity vibrations (phonon mode) cause modulation of the incident, continuous-wave (cw) input pump beam. Furthermore, with increasing cw pump power, an evolution from sinusoidal modulation to random oscillations is observed in the pump power coupled from the resonator. The temporal evolution with pump power is studied, and agreement was found with theory. In addition to applications in quantum optomechanics, the present work suggests that radiation-pressure-induced effects can establish a practical limit for the miniaturization of optical silica microcavities. DOI: 10.1103/PhysRevLett.94.223902 PACS numbers: 42.79.Jq, 42.55.Sa Optical cavities with walls pushed by radiation pressure (RP) have similar properties to cavities containing a Kerr medium [1] including hysteretic wavelength response caused by RP [2]. In particular, both RP and the Kerr effect induce a coupling between optical path length and light intensity, one through cavity strain and the other through the index of refraction. It is therefore not surprising that RP has been proposed as an alternative path for observation of quantum effects such as squeezing [1] and creation of EPR entangled pairs of photons [3]. Moreover, the nature of RP to act on a macroscopic object suggests that RP is a promising mechanism for entangling macroscopic mechanical oscillators [4], creating a Schrödinger cat state of a macroscopic mirror [5], teleportation of a macroscopic mechanical resonator state [6] and more.We present here a microscale device consisting only of an ultra-high-Q (UHQ) toroid cavity and a cw pump wave. The pressure of circulating radiation induces a mechanical flex of the cavity structure; this motion, in return, takes the optical cavity out of resonance with the cw pump wave, thereby lowering RP. Upon restoration of the mechanical flex, the process resumes, leading to a periodic motion of the cavity as well as the circulating power. It should be emphasized that this oscillation is regenerative, exhibiting classic threshold behavior and requiring no external temporal modulation of the pump wave. Recently, transmission oscillations were reported, which were shown to occur exactly at the mechanical eigenfrequencies of the cavity structure [7]. Here, we explore and explain both experimentally and theoretically the system's temporal behavior. In particular, it is shown that the output intensity of the system evolves from sinusoidal to a train of decaying peaks and finally to random oscillations as input cw pump power increases.It is also shown here that when the size of a silica cavity is small, oscillations can occur well before other nonlinear effects as well as before lasing due to the intentional doping of rare earths into the microcavities. Namely, we demonstrate that these regenerative vibrations can occur at pump powers lower than for Kerr parametric oscillation [...

Optomechanics

“…This will be the subject of the present section. These effects have already been observed in experiments Carmon et al, 2005;Kippenberg et al, 2005;Metzger et al, 2008).…”

Brillouin cavity optomechanics with microfluidic devices

“…3b), the inner surface experiences 16% displacement relative to the outer surface. [28][29][30][31] , as opposed to the travelling-wave vibrations in Fig. 3b-f.…”

Cavity optomechanics on a microfluidic resonator with water and viscous liquids

“…The inflating radiation pressure on the device walls is enhanced by the multiple optical recirculations and excites the vibrational breathe mode of the bubble in a self-sustained process. 14 Vibration, in return, modulates the circulating light in a manner that can be observed by a photodetector. We optically measure mechanical vibrations by coupling part of the resonator light that was circulating in the vibrating cavity through the other side of fibre to a photodetector (Figure 1e).…”

“…In this manner, when both mechanical and optical quality factors, Q m and Q O , of microdevices are sufficiently leveraged, their optical and mechanical modes can be parametrically coupled, allowing the optical excitation of vibrations. 14 In spherical shapes 9 such as our bubble, excitation of mechanical breathe modes, at 100 MHz rates, is expected via the centrifugal pressure applied by a circulating optical whispering-gallery mode. It is interesting that we could also observe some 1 GHz and 11 GHz modes in the same microfluidic device that were excited via a different mechanism as explained in Refs.…”