108 research outputs found
Phonon Bloch oscillations in acoustic-cavity structures
We describe a semiconductor multilayer structure based in acoustic phonon
cavities and achievable with MBE technology, designed to display acoustic
phonon Bloch oscillations. We show that forward and backscattering Raman
spectra give a direct measure of the created phononic Wannier-Stark ladder. We
also discuss the use of femtosecond laser impulsions for the generation and
direct probe of the induced phonon Bloch oscillations. We propose a gedanken
experiment based in an integrated phonon source-structure-detector device, and
we present calculations of pump and probe time dependent optical reflectivity
that evidence temporal beatings in agreement with the Wannier-Stark ladder
energy splitting.Comment: PDF file including 4 figure
Sub-Terahertz Monochromatic Transduction with Semiconductor Acoustic Nanodevices
We demonstrate semiconductor superlattices or nanocavities as narrow band
acoustic transducers in the sub-terahertz range. Using picosecond ultrasonics
experiments in the transmission geometry with pump and probe incident on
opposite sides of the thick substrate, phonon generation and detection
processes are fully decoupled. Generating with the semiconductor device and
probing on the metal, we show that both superlattices and nanocavities generate
spectrally narrow wavepackets of coherent phonons with frequencies in the
vicinity of the zone center and time durations in the nanosecond range,
qualitatively different from picosecond broadband pulses usually involved in
picosecond acoustics with metal generators. Generating in the metal and probing
on the nanoacoustic device, we furthermore evidence that both nanostructured
semiconductor devices may be used as very sensitive and spectrally selective
detectors
Anderson Photon-Phonon Colocalization in Certain Random Superlattices
International audienceFundamental observations in physics ranging from gravitational wave detection to laser cooling of a nanomechanical oscillator into its quantum ground state rely on the interaction between the optical and the mechanical degrees of freedom. A key parameter to engineer this interaction is the spatial overlap between the two fields, optimized in carefully designed resonators on a case-by-case basis. Disorder is an alternative strategy to confine light and sound at the nanoscale. However, it lacks an a priori mechanism guaranteeing a high degree of colocalization due to the inherently complex nature of the underlying interference processes. Here, we propose a way to address this challenge by using GaAs=AlAs vertical distributed Bragg reflectors with embedded geometrical disorder. Because of a remarkable coincidence in the physical parameters governing light and motion propagation in these two materials, the equations for both longitudinal acoustic waves and normal-incidence light become practically equivalent for excitations of the same wavelength. This guarantees spatial overlap between the electromagnetic and displacement fields of specific photon-phonon pairs, leading to strong light-matter interaction. In particular, a statistical enhancement in the vacuum optomechanical coupling rate, g o , is found, making this system a promising candidate to explore Anderson localization of high frequency (∼20 GHz) phonons enabled by cavity optomechanics. The colocalization effect shown here unlocks the access to unexplored localization phenomena and the engineering of light-matter interactions mediated by Anderson-localized states
Brillouin Scattering in Hybrid Optophononic Bragg Micropillar Resonators at 300 GHz
We introduce a monolithic Brillouin generator based on a semiconductor
micropillar cavity embedding a high frequency nanoacoustic resonator operating
in the hundreds of GHz range. The concept of two nested resonators allows an
independent design of the ultrahigh frequency Brillouin spectrum and of the
optical device. We develop an optical free-space technique to characterize
spontaneous Brillouin scattering in this monolithic device and propose a
measurement protocol that maximizes the Brillouin generation efficiency in the
presence of optically induced thermal effects. The compact and versatile
Brillouin generator studied here could be readily integrated into fibered and
on-chip architectures.Comment: 9 pages, 4 figure
Near optimal single photon sources in the solid state
Single-photons are key elements of many future quantum technologies, be it
for the realisation of large-scale quantum communication networks for quantum
simulation of chemical and physical processes or for connecting quantum
memories in a quantum computer. Scaling quantum technologies will thus require
efficient, on-demand, sources of highly indistinguishable single-photons.
Semiconductor quantum dots inserted in photonic structures are ultrabright
single photon sources, but the photon indistinguishability is limited by charge
noise induced by nearby surfaces. The current state of the art for
indistinguishability are parametric down conversion single-photon sources, but
they intrinsically generate multiphoton events and hence must be operated at
very low brightness to maintain high single photon purity. To date, no
technology has proven to be capable of providing a source that simultaneously
generates near-unity indistinguishability and pure single photons with high
brightness. Here, we report on such devices made of quantum dots in
electrically controlled cavity structures. We demonstrate on-demand, bright and
ultra-pure single photon generation. Application of an electrical bias on
deterministically fabricated devices is shown to fully cancel charge noise
effects. Under resonant excitation, an indistinguishability of
is evidenced with a . The photon
extraction of and measured brightness of make this source
times brighter than any source of equal quality. This new generation of
sources open the way to a new level of complexity and scalability in optical
quantum manipulation
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