91 research outputs found
Optomechanical transduction of an integrated silicon cantilever probe using a microdisk resonator
Sensitive transduction of the motion of a microscale cantilever is central to
many applications in mass, force, magnetic resonance, and displacement sensing.
Reducing cantilever size to nanoscale dimensions can improve the bandwidth and
sensitivity of techniques like atomic force microscopy, but current optical
transduction methods suffer when the cantilever is small compared to the
achievable spot size. Here, we demonstrate sensitive optical transduction in a
monolithic cavity-optomechanical system in which a sub-picogram silicon
cantilever with a sharp probe tip is separated from a microdisk optical
resonator by a nanoscale gap. High quality factor (Q ~ 10^5) microdisk optical
modes transduce the cantilever's MHz frequency thermally-driven vibrations with
a displacement sensitivity of ~ 4.4x10^-16 m\sqrt[2]{Hz} and bandwidth > 1 GHz,
and a dynamic range > 10^6 is estimated for a 1 s measurement.
Optically-induced stiffening due to the strong optomechanical interaction is
observed, and engineering of probe dynamics through cantilever design and
electrostatic actuation is illustrated
A circular dielectric grating for vertical extraction of single quantum dot emission
We demonstrate a nanostructure composed of partially etched annular trenches
in a suspended GaAs membrane, designed for efficient and moderately broadband
(approx. 5 nm) emission extraction from single InAs quantum dots. Simulations
indicate that a dipole embedded in the nanostructure center radiates upwards
into free space with a nearly Gaussian far-field, allowing a collection
efficiency > 80 % with a high numerical aperture (NA=0.7) optic, and with 12X
Purcell radiative rate enhancement. Fabricated devices exhibit an approx. 10 %
photon collection efficiency with a NA=0.42 objective, a 20X improvement over
quantum dots in unpatterned GaAs. A fourfold exciton lifetime reduction
indicates moderate Purcell enhancement.Comment: (3 pages
Efficient quantum dot single photon extraction into an optical fiber using a nanophotonic directional coupler
We demonstrate a spectrally broadband and effcient technique for collecting
photoluminescence from a single InAs quantum dot directly into a standard
single mode optical fiber. In this approach, an optical fiber taper waveguide
is placed in contact with a suspended GaAs nanophotonic waveguide with embedded
quantum dots, forming an effcient and broadband directional coupler with
standard optical fiber input and output. Effcient photoluminescence collection
over a wavelength range of tens of nanometers is demonstrated, and a maximum
collection effciency of 6.05 % (corresponding single photon rate of 3.0 MHz)
into a single mode optical fiber was estimated for a single quantum dot
exciton
Sympathetic cooling of a membrane oscillator in a hybrid mechanical-atomic system
Sympathetic cooling with ultracold atoms and atomic ions enables ultralow
temperatures in systems where direct laser or evaporative cooling is not
possible. It has so far been limited to the cooling of other microscopic
particles, with masses up to times larger than that of the coolant atom.
Here we use ultracold atoms to sympathetically cool the vibrations of a
SiN nanomembrane, whose mass exceeds that of the atomic ensemble by a
factor of . The coupling of atomic and membrane vibrations is mediated
by laser light over a macroscopic distance and enhanced by placing the membrane
in an optical cavity. We observe cooling of the membrane vibrations from room
temperature to mK, exploiting the large atom-membrane
cooperativity of our hybrid optomechanical system. Our scheme enables
ground-state cooling and quantum control of low-frequency oscillators such as
nanomembranes or levitated nanoparticles, in a regime where purely
optomechanical techniques cannot reach the ground state.Comment: 11 pages, 4 figure
Spectroscopy of mechanical dissipation in micro-mechanical membranes
We measure the frequency dependence of the mechanical quality factor (Q) of
SiN membrane oscillators and observe a resonant variation of Q by more than two
orders of magnitude. The frequency of the fundamental mechanical mode is tuned
reversibly by up to 40% through local heating with a laser. Several distinct
resonances in Q are observed that can be explained by coupling to membrane
frame modes. Away from the resonances, the background Q is independent of
frequency and temperature in the measured range.Comment: 4 pages, 5 figure
Long Distance Coupling of a Quantum Mechanical Oscillator to the Internal States of an Atomic Ensemble
We propose and investigate a hybrid optomechanical system consisting of a
micro-mechanical oscillator coupled to the internal states of a distant
ensemble of atoms. The interaction between the systems is mediated by a light
field which allows to couple the two systems in a modular way over long
distances. Coupling to internal degrees of freedom of atoms opens up the
possibility to employ high-frequency mechanical resonators in the MHz to GHz
regime, such as optomechanical crystal structures, and to benefit from the rich
toolbox of quantum control over internal atomic states. Previous schemes
involving atomic motional states are rather limited in both of these aspects.
We derive a full quantum model for the effective coupling including the main
sources of decoherence. As an application we show that sympathetic ground-state
cooling and strong coupling between the two systems is possible.Comment: 14 pages, 5 figure
Two-photon interference using background-free quantum frequency conversion of single photons from a semiconductor quantum dot
We show that quantum frequency conversion (QFC) can overcome the spectral
distinguishability common to inhomogeneously broadened solid-state quantum
emitters. QFC is implemented by combining single photons from an InAs quantum
dot (QD) at 980 nm with a 1550 nm pump laser in a periodically-poled lithium
niobate (PPLN) waveguide to generate photons at 600 nm with a
signal-to-background ratio exceeding 100:1. Photon correlation and two-photon
interference measurements confirm that both the single photon character and
wavepacket interference of individual QD states are preserved during frequency
conversion. Finally, we convert two spectrally separate QD transitions to the
same wavelength in a single PPLN waveguide and show that the resulting field
exhibits non-classical two-photon interference.Comment: Supercedes arXiv:1205.221
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