93 research outputs found
Observation of Kerr nonlinearity in microcavities at room temperature
We have devised and experimentally verified a method for observation of the optical Kerr effect in microcavities at room temperature. The technique discriminates against the much larger and typically dominant thermal component of nonlinearity by using its relatively slow frequency response. Measurement of the Kerr coefficient or equivalently of the third-order nonlinear susceptibility of the cavity material is demonstrated for a silica microcavity. With this approach, useful information about the characteristic thermal response time in microresonators can also be acquired
Ultralow Loss, High Q, Four Port Resonant Couplers for Quantum Optics and Photonics
We demonstrate a low-loss, optical four port resonant coupler (add-drop geometry), using ultrahigh Q (>108) toroidal microcavities. Different regimes of operation are investigated by variation of coupling between resonator and fiber taper waveguides. As a result, waveguide-to-waveguide power transfer efficiency of 93% (0.3 dB loss) and nonresonant insertion loss of 0.02% (<0.001 dB) for narrow bandwidth (57 MHz) four port couplers are achieved in this work. The combination of low-loss, fiber compatibility, and wafer-scale design would be suitable for a variety of applications ranging from quantum optics to photonic networks
Brownian noise in radiation-pressure-driven micromechanical oscillators
The authors demonstrate Brownian-noise-limited operation of an optomechanical oscillator, wherein mechanical oscillations of a silica optical microcavity are sustained by means of radiation pressure. Using phase noise measurement above threshold, it has been shown that the short-term linewidth of mechanical oscillations is fundamentally broadened, limited by thermal equipartition of energy
Scanning probe microscopy of thermally excited mechanical modes of an optical microcavity
The resonant buildup of light within optical microcavities elevates the
radiation pressure which mediates coupling of optical modes to the mechanical
modes of a microcavity. Above a certain threshold pump power, regenerative
mechanical oscillation occurs causing oscillation of certain mechanical
eigenmodes. Here, we present a methodology to spatially image the
micro-mechanical resonances of a toroid microcavity using a scanning probe
technique. The method relies on recording the induced frequency shift of the
mechanical eigenmode when in contact with a scanning probe tip. The method is
passive in nature and achieves a sensitivity sufficient to spatially resolve
the vibrational mode pattern associated with the thermally agitated
displacement at room temperature. The recorded mechanical mode patterns are in
good qualitative agreement with the theoretical strain fields as obtained by
finite element simulations
Theoretical and experimental study of radiation pressure-induced mechanical oscillations (parametric instability) in optical microcavities
Radiation pressure can couple the mechanical modes of an optical cavity structure to its optical modes, leading to parametric oscillation instability. This regime is characterized by regenerative oscillation of the mechanical cavity eigenmodes. Here, we present the first observation of this effect with a detailed theoretical and experimental analysis of these oscillations in ultra-high-Q microtoroids. Embodied within a microscale, chip-based device, this mechanism can benefit both research into macroscale quantum mechanical phenomena and improve the understanding of the mechanism within the context of laser interferometer gravitational-wave observatory (LIGO). It also suggests that new technologies are possible that will leverage the phenomenon within photonics
Characterization and scanning probe spectroscopy of radiation-pressure induced mechanical oscillation of a microcavity
Microcavities can enter a regime where radiation pressure causes oscillation of mechanical cavity eigenmodes. We present a detailed experimental and theoretical understanding of this effect, and report direct scanning probe spectroscopy of the micro-mechanical modes
Temporal Behavior of Radiation-Pressure-Induced Vibrations of an Optical Microcavity Phonon Mode
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
Analysis of radiation-pressure induced mechanical oscillation of an optical microcavity
The theoretical work of V.B. Braginsky predicted that radiation pressure can
couple the mechanical, mirror-eigenmodes of a Fabry-Perot 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
Feedback control of ultra-high-Q microcavities: application to micro-Raman lasers and microparametric oscillators
We demonstrate locking of an on-chip, high-Q toroidal-cavity to a pump laser using two, distinct methods: coupled power stabilization and wavelength locking of pump laser to the microcavity. In addition to improvements in operation of previously demonstrated micro-Raman and micro-OPO lasers, these techniques have enabled observation of a continuous, cascaded nonlinear process in which photons generated by optical parametric oscillations (OPO) function as a pump for Raman lasing. Dynamical behavior of the feedback control systems is also shown including the interplay between the control loop and the thermal nonlinearity. The demonstrated stabilization loop is essential for studying generation of nonclassical states using a microcavity optical parametric oscillator
Opto-Mechanical Modal Spectroscopy: Opto-Excited Vibrations of a Micron-Scale On-Chip Resonator
Centrifugal radiation pressure excites vibrational modes of cavity at the GHz range. Many spectral lines associated with high-order vibrational modes are measured. Perturbation is observed to induce fine split of the spectral line
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