382 research outputs found
Cavity optomechanics with ultra-high Q crystalline micro-resonators
We present the first observation of optomechanical coupling in ultra-high Q
crystalline whispering-gallery-mode (WGM) resonators. The high purity of the
crystalline material enables optical quality factors in excess of 10^{10} and
finesse exceeding 10^{6}. Simultaneously, mechanical quality factors greater
than 10^{5} are obtained, still limited by clamping losses. Compared to
previously demonstrated cylindrical resonators, the effective mass of the
mechanical modes can be dramatically reduced by the fabrication of CaF2
microdisc resonators. Optical displacement monitoring at the 10^{-18}
m/sqrt{Hz}-level reveals mechanical radial modes at frequencies up to 20 MHz,
corresponding to unprecedented sideband factors (>100). Together with the weak
intrinsic mechanical damping in crystalline materials, such high sindeband
factors render crystalline WGM micro-resonators promising for backaction
evading measurements, resolved sideband cooling or optomechanical normal mode
splitting. Moreover, these resonators can operate in a regime where
optomechanical Brillouin lasing can become accessible
Frequency combs and platicons in optical microresonators with normal GVD
We predict the existence of a novel type of the flat-top dissipative
solitonic pulses, "platicons", in microresonators with normal group velocity
dispersion (GVD). We propose methods to generate these platicons from cw pump.
Their duration may be altered significantly by tuning the pump frequency. The
transformation of a discrete energy spectrum of dark solitons of the
Lugiato-Lefever equation into a quasicontinuous spectrum of platicons is
demonstrated. Generation of similar structures is also possible with
bi-harmonic, phase/amplitude modulated pump or via laser injection locking.Comment: 9 pages, 6 figure
Mode spectrum and temporal soliton formation in optical microresonators
The formation of temporal dissipative solitons in optical microresonators
enables compact, high repetition rate sources of ultra-short pulses as well as
low noise, broadband optical frequency combs with smooth spectral envelopes.
Here we study the influence of the resonator mode spectrum on temporal soliton
formation. Using frequency comb assisted diode laser spectroscopy, the measured
mode structure of crystalline MgF2 resonators are correlated with temporal
soliton formation. While an overal general anomalous dispersion is required, it
is found that higher order dispersion can be tolerated as long as it does not
dominate the resonator's mode structure. Mode coupling induced avoided
crossings in the resonator mode spectrum are found to prevent soliton
formation, when affecting resonator modes close to the pump laser. The
experimental observations are in excellent agreement with numerical simulations
based on the nonlinear coupled mode equations, which reveal the rich interplay
of mode crossings and soliton formation
Determination of the vacuum optomechanical coupling rate using frequency noise calibration
The strength of optomechanical interactions in a cavity optomechanical system
can be quantified by a vacuum coupling rate \vcr analogous to cavity quantum
electrodynamics. This single figure of merit removes the ambiguity in the
frequently quoted coupling parameter defining the frequency shift for a given
mechanical displacement, and the effective mass of the mechanical mode. Here we
demonstrate and verify a straightforward experimental technique to derive the
vacuum optomechanical coupling rate. It only requires applying a known
frequency modulation of the employed electromagnetic probe field and knowledge
of the mechanical oscillator's occupation. The method is experimentally
verified for a micromechanical mode in a toroidal whispering-gallery-resonator
and a nanomechanical oscillator coupled to a toroidal cavity via its near
field.Comment: 11 pages, 2 figure
Soliton dual comb in crystalline microresonators
We present a novel compact dual-comb source based on a monolithic optical
crystalline MgF multi-resonator stack. The coherent soliton combs generated
in two microresonators of the stack with the repetition rate of 12.1 GHz and
difference of 1.62 MHz provided after heterodyning a 300 MHz wide
radio-frequency comb. Analogous system can be used for dual-comb spectroscopy,
coherent LIDAR applications and massively parallel optical communications.Comment: 5 pages, 5 figure
High-sensitivity monitoring of micromechanical vibration using optical whispering gallery mode resonators
The inherent coupling of optical and mechanical modes in high finesse optical
microresonators provide a natural, highly sensitive transduction mechanism for
micromechanical vibrations. Using homodyne and polarization spectroscopy
techniques, we achieve shot-noise limited displacement sensitivities of
10^(-19) m Hz^(-1/2). In an unprecedented manner, this enables the detection
and study of a variety of mechanical modes, which are identified as radial
breathing, flexural and torsional modes using 3-dimensional finite element
modelling. Furthermore, a broadband equivalent displacement noise is measured
and found to agree well with models for thermorefractive noise in silica
dielectric cavities. Implications for ground-state cooling, displacement
sensing and Kerr squeezing are discussed.Comment: 25 pages, 8 figure
Coupling ideality of free electrons with photonic integrated waveguides
Recently, integrated photonics has brought new capabilities to electron microscopy and been used to demonstrate efficient electron phase modulation and electron-photon correlations. Here, we quantitatively analyze the interaction strength between a free electron and a photonic integrated circuit with a heterogeneous structure. We adopt a dissipative QED treatment and show that with proper electron beam positioning and waveguide geometry, one can achieve near-unity coupling ideality to a well-defined spatial-temporal waveguide mode. Furthermore, we show that the frequency and waveform of the coupled mode can be tailored to the application. These features show that photonic integrated waveguides are a promising platform for free-electron quantum optics with applications like high-fidelity electron-photon entanglement, heralded single-electron and photon state synthesis
Local correlations in the 1D Bose gas from a scaling limit of the XXZ chain
We consider the K-body local correlations in the (repulsive) 1D Bose gas for
general K, both at finite size and in the thermodynamic limit. Concerning the
latter we develop a multiple integral formula which applies for arbitrary
states of the system with a smooth distribution of Bethe roots, including the
ground state and finite temperature Gibbs-states. In the cases K<=4 we perform
the explicit factorization of the multiple integral. In the case of K=3 we
obtain the recent result of Kormos et.al., whereas our formula for K=4 is new.
Numerical results are presented as well.Comment: 23 pages, 2 figures, v2: minor modifications and references adde
Cryogenic properties of optomechanical silica microcavities
We present the optical and mechanical properties of high-Q fused silica
microtoroidal resonators at cryogenic temperatures (down to 1.6 K). A thermally
induced optical multistability is observed and theoretically described; it
serves to characterize quantitatively the static heating induced by light
absorption. Moreover the influence of structural defect states in glass on the
toroid mechanical properties is observed and the resulting implications of
cavity optomechanical systems on the study of mechanical dissipation discussed.Comment: 4 pages, 3 figure
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
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