440 research outputs found
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
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
Wavelength-independent coupler from fiber to an on-chip cavity, demonstrated over an 850nm span
A robust wide band (850 nm) fiber coupler to a whispering-gallery cavity with ultra-high quality factor is experimentally demonstrated. The device trades off ideality for broad-band, efficient input coupling. Output coupling efficiency can remain high enough for practical applications wherein pumping and power extraction must occur over very broad wavelength spans
Observation of Spontaneous Brillouin Cooling
While radiation-pressure cooling is well known, the Brillouin scattering of
light from sound is considered an acousto-optical amplification-only process.
It was suggested that cooling could be possible in multi-resonance Brillouin
systems when phonons experience lower damping than light. However, this regime
was not accessible in traditional Brillouin systems since backscattering
enforces high acoustical frequencies associated with high mechanical damping.
Recently, forward Brillouin scattering in microcavities has allowed access to
low-frequency acoustical modes where mechanical dissipation is lower than
optical dissipation, in accordance with the requirements for cooling. Here we
experimentally demonstrate cooling via such a forward Brillouin process in a
microresonator. We show two regimes of operation for the Brillouin process:
acoustical amplification as is traditional, but also for the first time, a
Brillouin cooling regime. Cooling is mediated by an optical pump, and scattered
light, that beat and electrostrictively attenuate the Brownian motion of the
mechanical mode.Comment: Supplementary material include
Nonreciprocal Phonon Laser
We propose nonreciprocal phonon lasing in a coupled cavity system composed of
an optomechanical and a spinning resonator. We show that the optical Sagnac
effect leads to significant modifications in both the mechanical gain and the
power threshold for phonon lasing. More importantly, the phonon lasing in this
system is unidirectional, that is the phonon lasing takes place when the
coupled system is driven in one direction but not the other. Our work
establishes the potential of spinning optomechanical devices for low-power
mechanical isolation and unidirectional amplification. This provides a new
route, well within the reach of current experimental abilities, to operate
cavity optomechanics devices for such a wide range of applications as
directional phonon switches, invisible sound sensing, and topological or chiral
acoustics.Comment: 10 pages, 4 figures; accepted by Physical Review Applie
Actuation of Micro-Optomechanical Systems Via Cavity-Enhanced Optical Dipole Forces
We demonstrate a new type of optomechanical system employing a movable,
micron-scale waveguide evanescently-coupled to a high-Q optical microresonator.
Micron-scale displacements of the waveguide are observed for
milliwatt(mW)-level optical input powers. Measurement of the spatial variation
of the force on the waveguide indicates that it arises from a cavity-enhanced
optical dipole force due to the stored optical field of the resonator. This
force is used to realize an all-optical tunable filter operating with sub-mW
control power. A theoretical model of the system shows the maximum achievable
force to be independent of the intrinsic Q of the optical resonator and to
scale inversely with the cavity mode volume, suggesting that such forces may
become even more effective as devices approach the nanoscale.Comment: 4 pages, 5 figures. High resolution version available at
(http://copilot.caltech.edu/publications/CEODF_hires.pdf). For associated
movie, see (http://copilot.caltech.edu/research/optical_forces/index.htm
Stimulated optomechanical excitation of surface acoustic waves in a microdevice
Stimulated Brillouin interaction between sound and light, known to be the
strongest optical nonlinearity common to all amorphous and crystalline
dielectrics, has been widely studied in fibers and bulk materials but rarely in
optical microresonators. The possibility of experimentally extending this
principle to excite mechanical resonances in photonic microsystems, for sensing
and frequency reference applications, has remained largely unexplored. The
challenge lies in the fact that microresonators inherently have large free
spectral range, while the phase matching considerations for the Brillouin
process require optical modes of nearby frequencies but with different
wavevectors. We rely on high-order transverse optical modes to relax this
limitation. Here we report on the experimental excitation of mechanical
resonances ranging from 49 to 1400 MHz by using forward Brillouin scattering.
These natural mechanical resonances are excited in ~100 um silica microspheres,
and are of a surface-acoustic whispering-gallery type
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