251 research outputs found
Compact, fiber-compatible, cascaded Raman laser
Cascaded Raman Stokes lasing in an ultrahigh-Q silica microsphere resonator coupled to a tapered fiber is demonstrated and analyzed. With less than 900 ÎĽW of pump power near 980 nm, five cascaded Stokes lasing lines are generated. In addition, a threshold power of 56.4 ÎĽW for the first-order Stokes lasing is achieved. The Stokes lasing lines exhibit distinct characteristics depending on their order, as predicted by theoretical analysis
Nonlinear states and dynamics in a synthetic frequency dimension
Recent advances in the study of synthetic dimensions revealed a possibility
to employ the frequency space as an additional degree of freedom which allows
for investigating and exploiting higher-dimensional phenomena in a priori
low-dimensional systems. However, the influence of nonlinear effects on the
synthetic frequency dimensions was studied only under significant restrictions.
In the present paper, we develop a generalized mean-field model for the optical
field envelope inside a single driven-dissipative resonator with quadratic and
cubic nonlinearities, whose frequencies are coupled via an electro-optical
resonant temporal modulation. The leading order equation takes the form of
driven Gross-Pitaevskii equation with a cosine potential. We numerically
investigate the nonlinear dynamics in such microring resonator with a synthetic
frequency dimension in the regime where parametric frequency conversion occurs.
In the case of anomalous dispersion, we find that the presence of
electro-optical mode coupling confines and stabilizes the chaotic modulation
instability region. This leads to the appearance of a novel type of stable
coherent structures which emerge in the synthetic space with restored
translational symmetry, in a region of parameters where conventionally only
chaotic modulation instability states exist. This structure appears in the
center of the synthetic band and, therefore, is referred to as Band Soliton.
Finally, we extend our results to the case of multiple modulation frequencies
with controllable relative phases creating synthetic lattices with nontrivial
geometry. We show that an asymmetric synthetic band leads to the coexistence of
chaotic and coherent states of the electromagnetic field inside the cavity i.e.
dynamics that can be interpreted as chimera-like states. Recently developed
microresonators can open the way to experimentally explore our
findings.Comment: 12 pages, 5 figures; figure 4 and typos correcte
Molecular cavity optomechanics: a theory of plasmon-enhanced Raman scattering
The conventional explanation of plasmon-enhanced Raman scattering attributes
the enhancement to the antenna effect focusing the electromagnetic field into
sub-wavelength volumes. Here we introduce a new model that additionally
accounts for the dynamical and coherent nature of the plasmon-molecule
interaction and thereby reveals an enhancement mechanism not contemplated
before: dynamical backaction amplification of molecular vibrations. We first
map the problem onto the canonical model of cavity optomechanics, in which the
molecular vibration and the plasmon are \textit{parametrically coupled}. The
optomechanical coupling rate, from which we derive the Raman cross section, is
computed from the molecules Raman activities and the plasmonic field
distribution. When the plasmon decay rate is comparable or smaller than the
vibrational frequency and the excitation laser is blue-detuned from the plasmon
onto the vibrational sideband, the resulting delayed feedback force can lead to
efficient parametric amplification of molecular vibrations. The optomechanical
theory provides a quantitative framework for the calculation of enhanced
cross-sections, recovers known results, and enables the design of novel systems
that leverage dynamical backaction to achieve additional, mode-selective
enhancement. It yields a new understanding of plasmon-enhanced Raman scattering
and opens a route to molecular quantum optomechanics.Comment: Extensively revised and improved version thanks to the hard work and
constructive comments of a careful Referee. Includes Supplemental Materia
Theoretical and experimental study of stimulated and cascaded Raman scattering in ultra-high-Q optical microcavities
Stimulated Raman scattering (SRS) in ultra-high-Q surface-tension-induced
spherical and chip-based toroid microcavities is considered both theoretically
and experimentally. These microcavities are fabricated from silica, exhibit
small mode volume (typically 1000 ) and possess whispering-gallery
type modes with long photon storage times (in the range of 100 ns),
significantly reducing the threshold for stimulated nonlinear optical
phenomena. Oscillation threshold levels of less than 100 % -Watts of
launched fiber pump power, in microcavities with quality factors of 100 million
are observed. Using a steady state analysis of the coupled-mode equations for
the pump and Raman whispering-gallery modes, the threshold, efficiencies and
cascading properties of SRS in UHQ devices are derived. The results are
experimentally confirmed in the telecommunication band (1550nm) using tapered
optical fibers as highly efficient waveguide coupling elements for both pumping
and signal extraction. The device performance dependence on coupling, quality
factor and modal volume are measured and found to be in good agreement with
theory. This includes analysis of the threshold and efficiency for cascaded
Raman scattering. The side-by-side study of nonlinear oscillation in both
spherical microcavities and toroid microcavities on-a-chip also allows for
comparison of their properties. In addition to the benefits of a wafer-scale
geometry, including integration with optical, electrical or mechanical
functionality, microtoroids on-a-chip exhibit single mode Raman oscillation
over a wide range of pump powers.Comment: 12 pages, 15 figure
Radiation Hardness of High-Q Silicon Nitride Microresonators for Space Compatible Integrated Optics
Integrated optics has distinct advantages for applications in space because
it integrates many elements onto a monolithic, robust chip. As the development
of different building blocks for integrated optics advances, it is of interest
to answer the important question of their resistance with respect to ionizing
radiation. Here we investigate effects of proton radiation on high-Q silicon
nitride microresonators formed by a waveguide ring. We show that the
irradiation with high-energy protons has no lasting effect on the linear
optical losses of the microresonators
Nonlinear Quantum Optomechanics via Individual Intrinsic Two-Level Defects
We propose to use the intrinsic two-level system (TLS) defect states found
naturally in integrated optomechanical devices for exploring cavity QED-like
phenomena with localized phonons. The Jaynes-Cummings-type interaction between
TLS and mechanics can reach the strong coupling regime for existing
nano-optomechanical systems, observable via clear signatures in the
optomechanical output spectrum. These signatures persist even at finite
temperature, and we derive an explicit expression for the temperature at which
they vanish. Further, the ability to drive the defect with a microwave field
allows for realization of phonon blockade, and the available controls are
sufficient to deterministically prepare non-classical states of the mechanical
resonator.Comment: Comments welcome (5+7 pages), Final Published Versio
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
Heralded single phonon preparation, storage and readout in cavity optomechanics
We analyze theoretically how to use the radiation pressure coupling between a
mechanical oscillator and an optical cavity field to generate in a heralded way
a single quantum of mechanical motion (a Fock state), and release on-demand the
stored excitation as a single photon. Starting with the oscillator close to its
ground state, a laser pumping the upper motional sideband leads to dynamical
backaction amplification and to the creation of correlated photon-phonon pairs.
The detection of one Stokes photon thus projects the macroscopic oscillator
into a single-phonon Fock state. The non-classical nature of this mechanical
state can be demonstrated by applying a readout laser on the lower sideband
(i.e. optical cooling) to map the phononic state to a photonic mode, and by
performing an autocorrelation measurement on the anti-Stokes photons. We
discuss the relevance of our proposal for the future of cavity optomechanics as
an enabling quantum technology.Comment: Accepted for publication in Physical Review Letters. Added References
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