The theoretical work of V.B. Braginsky predicted that radiation pressure can couple the mechanical, mirror-eigenmodes of a Fabry-Pérot resonator to it's optical modes, leading to a parametric oscillation instability. This regime is characterized by regenerative mechanical oscillation of the mechanical mirror eigenmodes. We have recently observed the excitation of mechanical modes in an ultra-high-Q optical microcavity. Here, we present a detailed experimental analysis of this effect and demonstrate that radiation pressure is the excitation mechanism of the observed mechanical oscillations.

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 [...

As stability and continuous operation are important for almost any use of a microcavity, we demonstrate here experimentally and theoretically a self-stable equilibrium solution for a pump-microcavity system. In this stable equilibrium, intensity-and wavelength-perturbations cause a small thermal resonant-drift that is enough to compensate for the perturbation (noises); consequently the cavity stays warm and loaded as perturbations are self compensated. We also compare here, our theoretical prediction for the thermal line broadening (and for the wavelength hysteretic response) to experimental results.

We present an experimental study on wave propagation in highly nonlocal optically nonlinear media, for which far-away boundary conditions significantly affect the evolution of localized beams. As an example, we set the boundary conditions to be anisotropic and demonstrate the first experimental observation of coherent elliptic solitons. Furthermore, exploiting the natural ability of such nonlinearities to eliminate azimuthal instabilities, we perform the first observation of stable vortex-ring solitons. These features of highly nonlocal nonlinearities affected by far-away boundary conditions open new directions in nonlinear science by facilitating remote control over soliton propagation. DOI: 10.1103/PhysRevLett.95.213904 PACS numbers: 42.65.Tg, 42.65.Jx, 47.27.Te Nonlocality plays an important role in many areas of nonlinear physics. Nonlocality typically arises from an underlying transport mechanism (heat [1], atoms in a gas [2], charge carriers [3,4], etc.) or from long-range forces (e.g., electrostatic interactions in liquid crystals [5]) and many-body interactions as with matter waves in BoseEinstein condensates [6] or plasma waves [7]. In nonlinear optics specifically, nonlocality was found in photorefractives [3,[8][9][10], in thermal nonlinear media [11][12][13][14], in atomic vapors [2], and in liquid crystals [5,15]. In principle, nonlocality acts to spread out the effects of localized excitations, and as such it can suppress modulation instabilities of homogeneous states [16]. However, in spite of the natural ''averaging'' tendency inherent to nonlocality, even highly nonlocal nonlinear media can support solitons [2,5,[17][18][19][20]. Moreover, it was suggested that nonlocality can prevent the catastrophic collapse of self-focused beams, allowing 2 1 D solitons in Kerr-type media [2,17,21]. In a similar vein, it was proposed that nonlocality can suppress azimuthal instabilities of vortex-ring beams [22,23], but such an experiment has thus far never been reported. Finally, nonlocality can considerably alter soliton interactions, e.g., giving rise to attraction between out of phase solitons [19,20,24] and between dark solitons [25], which without nonlocality always repel, and causing attraction between well separated solitons [26].Here we present an experimental study on solitons in a nonlinear medium with an extremely large range of nonlocality, such that far-away boundary conditions directly affect the soliton beam. We use the thermal optical nonlinearity in lead glass, which is of the self-focusing type. The nonlocal nature of this thermal nonlinearity is manifested in the heat-transfer (Poisson-type) equation, for which boundary conditions greatly influence the temperature distribution. The nonlinear index change is proportional to the temperature change; hence, the boundary conditions, even from afar, significantly affect the refractive index structure supporting solitons. We show that setting transversely anisotropic boundary conditions (e.g., rectangular boundaries in the transverse plane) f...

We report the first experimental observation of discrete solitons in an array of optically induced waveguides. The waveguide lattice is induced in real time by illuminating a photorefractive crystal with a pair of interfering plane waves. We demonstrate two types of bright discrete solitons: in-phase self-localized states and the staggered (pi out-of-phase) soliton family. This experiment is the first observation of bright staggered solitons in any physical system. Our scheme paves the way for reconfigurable focusing and defocusing photonic lattices where low-power (mW) discrete solitons can be thoroughly investigated.