455 research outputs found
Optomechanically induced transparency and cooling in thermally stable diamond microcavities
Diamond cavity optomechanical devices hold great promise for quantum
technology based on coherent coupling between photons, phonons and spins. These
devices benefit from the exceptional physical properties of diamond, including
its low mechanical dissipation and optical absorption. However the nanoscale
dimensions and mechanical isolation of these devices can make them susceptible
to thermo-optic instability when operating at the high intracavity field
strengths needed to realize coherent photon--phonon coupling. In this work, we
overcome these effects through engineering of the device geometry, enabling
operation with large photon numbers in a previously thermally unstable regime
of red-detuning. We demonstrate optomechanically induced transparency with
cooperativity > 1 and normal mode cooling from 300 K to 60 K, and predict that
these device will enable coherent optomechanical manipulation of diamond spin
systems
Single-crystal diamond low-dissipation cavity optomechanics
Single-crystal diamond cavity optomechanical devices are a promising example
of a hybrid quantum system: by coupling mechanical resonances to both light and
electron spins, they can enable new ways for photons to control solid state
qubits. However, realizing cavity optomechanical devices from high quality
diamond chips has been an outstanding challenge. Here we demonstrate
single-crystal diamond cavity optomechanical devices that can enable
photon-phonon-spin coupling. Cavity optomechanical coupling to
frequency () mechanical resonances is observed. In room temperature
ambient conditions, these resonances have a record combination of low
dissipation (mechanical quality factor, ) and high
frequency, with sufficient
for room temperature single phonon coherence. The system exhibits high optical
quality factor () resonances at infrared and visible
wavelengths, is nearly sideband resolved, and exhibits optomechanical
cooperativity . The devices' potential for optomechanical control of
diamond electron spins is demonstrated through radiation pressure excitation of
mechanical self-oscillations whose 31 pm amplitude is predicted to provide 0.6
MHz coupling rates to diamond nitrogen vacancy center ground state transitions
(6 Hz / phonon), and stronger coupling rates to excited state
transitions.Comment: 12 pages, 5 figure
Single crystal diamond nanobeam waveguide optomechanics
Optomechanical devices sensitively transduce and actuate motion of
nanomechanical structures using light. Single--crystal diamond promises to
improve the performance of optomechanical devices, while also providing
opportunities to interface nanomechanics with diamond color center spins and
related quantum technologies. Here we demonstrate dissipative
waveguide--optomechanical coupling exceeding 35 GHz/nm to diamond nanobeams
supporting both optical waveguide modes and mechanical resonances, and use this
optomechanical coupling to measure nanobeam displacement with a sensitivity of
fm/ and optical bandwidth nm. The nanobeams are
fabricated from bulk optical grade single--crystal diamond using a scalable
undercut etching process, and support mechanical resonances with quality factor
at room temperature, and in cryogenic
conditions (5K). Mechanical self--oscillations, resulting from interplay
between photothermal and optomechanical effects, are observed with amplitude
exceeding 200 nm for sub-W absorbed optical power, demonstrating the
potential for optomechanical excitation and manipulation of diamond
nanomechanical structures.Comment: Minor changes. Corrected error in units of applied stress in Fig. 1
Efficient telecom to visible wavelength conversion in doubly resonant GaP microdisks
Resonant second harmonic generation between 1550 nm and 775 nm with outside
efficiency is demonstrated in a gallium
phosphide microdisk cavity supporting high- modes at visible ()
and infrared () wavelengths. The double resonance condition was
satisfied through intracavity photothermal temperature tuning using W of 1550 nm light input to a fiber taper and resonantly coupled to
the microdisk. Above this pump power efficiency was observed to decrease. The
observed behavior is consistent with a simple model for thermal tuning of the
double resonance condition.Comment: 6 pages, 4 figure
Realizing > 300,000 in diamond microdisks for optomechanics via etch optimization
Nanophotonic structures in single--crystal diamond (SCD) that simultaneously
confine and co-localize photons and phonons are highly desirable for
applications in quantum information science and optomechanics. Here we describe
an optimized process for etching SCD microdisk structures designed for
optomechanics applications. This process allows the optical quality factor,
, of these devices to be enhanced by a factor of 4 over previous
demonstrations to , which is sufficient to enable sideband
resolved coherent cavity optomechanical experiments. Through analysis of
optical loss and backscattering rates we find that remains limited by
surface imperfections. We also describe a technique for altering microdisk
pedestal geometry which could enable reductions in mechanical dissipation.Comment: Published versio
Comparison of Different Minimal Velocity Thresholds to Establish Deadlift One Repetition Maximum
The aim of this study was to compare the actual deadlift one repetition maximum (1RM)
and the deadlift 1RM predicted from individualised load-velocity profiles. Twelve moderately
resistance-trained men participated in three deadlift sessions. During the first, 1RM was assessed;
during the second, load-velocity profiles were recorded with six loads (65% to 90% 1RM) using
a linear position transducer recording at 1000 Hz; and during the third, minimal velocity thresholds
(MVT) were recorded from the velocity of the last repetition during sets to volitional fatigue with 70%
and 80% 1RM with a linear position transducer recording at 1000 Hz. Regression was then used to
generate individualised load-velocity profiles and the MVT was used as a cut-off value from which
to predict deadlift 1RM. In general, velocity reliability was poor to moderate. More importantly,
predicted deadlift 1RMs were significantly and meaningfully less than actual deadlift 1RMs (p < 0.05,
d = 1.03–1.75). The main practical application that should be taken from the results of this study is that
individualized load-velocity profiles should not be used to predict deadlift 1RM. Practitioners should
not use this method in combination with the application of MVT obtained from the last repetition of
sets to volitional fatigue
Dissipative and Dispersive Optomechanics in a Nanocavity Torque Sensor
Dissipative and dispersive optomechanical couplings are experimentally
observed in a photonic crystal split-beam nanocavity optimized for detecting
nanoscale sources of torque. Dissipative coupling of up to approximately
MHz/nm and dispersive coupling of GHz/nm enable measurements of sub-pg
torsional and cantilever-like mechanical resonances with a thermally-limited
torque detection sensitivity of 1.2 in ambient conditions and 1.3 in low vacuum. Interference between
optomechanical coupling mechanisms is observed to enhance detection sensitivity
and generate a mechanical-mode-dependent optomechanical wavelength response.Comment: 11 pages, 6 figure
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