520 research outputs found
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
Modal coupling in traveling-wave resonators
High-Q traveling-wave-resonators can enter a regime in which even minute scattering amplitudes associated with either bulk or surface imperfections can drive the system into the so-called strong modal coupling regime. Resonators that enter this regime have their coupling properties radically altered and can mimic a narrowband reflector. We experimentally confirm recently predicted deviations from criticality in such strongly coupled systems. Observations of resonators that had Q>10^8 and modal coupling parameters as large as 30 were shown to reflect more than 94% of an incoming optical signal within a narrow bandwidth of 40 MHz
Evanescent straight tapered-fiber coupling of ultra-high Q optomechanical micro-resonators in a low-vibration helium-4 exchange-gas cryostat
We developed an apparatus to couple a 50-micrometer diameter
whispering-gallery silica microtoroidal resonator in a helium-4 cryostat using
a straight optical tapered-fiber at 1550nm wavelength. On a top-loading probe
specifically adapted for increased mechanical stability, we use a
specifically-developed "cryotaper" to optically probe the cavity, allowing thus
to record the calibrated mechanical spectrum of the optomechanical system at
low temperatures. We then demonstrate excellent thermalization of a 63-MHz
mechanical mode of a toroidal resonator down to the cryostat's base temperature
of 1.65K, thereby proving the viability of the cryogenic refrigeration via heat
conduction through static low-pressure exchange gas. In the context of
optomechanics, we therefore provide a versatile and powerful tool with
state-of-the-art performances in optical coupling efficiency, mechanical
stability and cryogenic cooling.Comment: 8 pages, 6 figure
Photonic clocks, Raman lasers, and Biosensors on Silicon
Micro-resonators on silicon having Q factors as high as 500 million are described, and used to demonstrate radio-frequency mechanical oscillators, micro-Raman and parametric sources with sub-100 microwatt thresholds, visible sources, as well as high-sensitivity, biological detectors
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
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
Mid-Infrared ultra-high-Q resonators based on fluoride crystalline materials
Decades ago, the losses of glasses in the near infrared (near-IR) were
investigated in views of developments for optical telecommunications. Today,
properties in the mid-infrared (mid-IR) are of interest for molecular
spectroscopy applications. In particular, high-sensitivity spectroscopic
techniques based on high-finesse mid-IR cavities hold high promise for medical
applications. Due to exceptional purity and low losses, whispering gallery mode
microresonators based on polished alkaline earth metal fluoride crystals (i.e
the family, where X Ca, Mg, Ba, Sr,...) have attained
ultra-high quality (Q) factor resonances (Q10) in the near-IR and
visible spectral ranges. Here we report for the first time ultra-high Q factors
in the mid-IR using crystalline microresonators. Using an uncoated chalcogenide
(ChG) tapered fiber, light from a continuous wave quantum cascade laser (QCL)
is efficiently coupled to several crystalline microresonators at 4.4 m
wavelength. We measure the optical Q factor of fluoride crystals in the mid-IR
using cavity ringdown technique. We observe that
microresonators feature quality factors that are very close to the fundamental
absorption limit, as caused by the crystal's multiphonon absorption
(Q10), in contrast to near-IR measurements far away from these
fundamental limits. Due to lower multiphonon absorption in and
, we show that ultra-high quality factors of Q 1.4
can be reached at 4.4 m. This corresponds to an optical
finesse of 4 10, the highest value achieved for any
type of mid-IR resonator to date, and a more than 10-fold improvement over the
state-of-the-art. Such compact ultra-high Q crystalline microresonators provide
a route for narrow linewidth frequency-stabilized QCL or mid-IR Kerr comb
generation.Comment: C. Lecaplain and C. Javerzac-Galy contributed equally to this wor
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
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