40 research outputs found
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
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
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
Thermo-optic locking of a semiconductor laser to a microcavity resonance
We experimentally demonstrate thermo-optic locking of a semiconductor laser
to an integrated toroidal optical microresonator. The lock is maintained for
time periods exceeding twelve hours, without requiring any electronic control
systems. Fast control is achieved by optical feedback induced by scattering
centers within the microresonator, with thermal locking due to optical heating
maintaining constructive interference between the cavity and the laser.
Furthermore, the optical feedback acts to narrow the laser linewidth, with
ultra high quality microtoroid resonances offering the potential for ultralow
linewidth on-chip lasers.Comment: 6 pages, 6 figure
Resolved Sideband Cooling of a Micromechanical Oscillator
Micro- and nanoscale opto-mechanical systems provide radiation pressure
coupling of optical and mechanical degree of freedom and are actively pursued
for their ability to explore quantum mechanical phenomena of macroscopic
objects. Many of these investigations require preparation of the mechanical
system in or close to its quantum ground state. Remarkable progress in ground
state cooling has been achieved for trapped ions and atoms confined in optical
lattices. Imperative to this progress has been the technique of resolved
sideband cooling, which allows overcoming the inherent temperature limit of
Doppler cooling and necessitates a harmonic trapping frequency which exceeds
the atomic species' transition rate. The recent advent of cavity back-action
cooling of mechanical oscillators by radiation pressure has followed a similar
path with Doppler-type cooling being demonstrated, but lacking inherently the
ability to attain ground state cooling as recently predicted. Here we
demonstrate for the first time resolved sideband cooling of a mechanical
oscillator. By pumping the first lower sideband of an optical microcavity,
whose decay rate is more than twenty times smaller than the eigen-frequency of
the associated mechanical oscillator, cooling rates above 1.5 MHz are attained.
Direct spectroscopy of the motional sidebands reveals 40-fold suppression of
motional increasing processes, which could enable reaching phonon occupancies
well below unity (<0.03). Elemental demonstration of resolved sideband cooling
as reported here should find widespread use in opto-mechanical cooling
experiments. Apart from ground state cooling, this regime allows realization of
motion measurement with an accuracy exceeding the standard quantum limit.Comment: 13 pages, 5 figure