40 research outputs found
Phonon engineering with superlattices: generalized nanomechanical potentials
Earlier implementations to simulate coherent wave propagation in
one-dimensional potentials using acoustic phonons with gigahertz-terahertz
frequencies were based on coupled nanoacoustic resonators. Here, we generalize
the concept of adiabatic tuning of periodic superlattices for the
implementation of effective one-dimensional potentials giving access to cases
that cannot be realized by previously reported phonon engineering approaches,
in particular the acoustic simulation of electrons and holes in a quantum well
or a double well potential. In addition, the resulting structures are much more
compact and hence experimentally feasible. We demonstrate that potential
landscapes can be tailored with great versatility in these multilayered
devices, apply this general method to the cases of parabolic, Morse and
double-well potentials and study the resulting stationary phonon modes. The
phonon cavities and potentials presented in this work could be probed by
all-optical techniques like pump-probe coherent phonon generation and Brillouin
scattering
Strong Optical-Mechanical Coupling in a Vertical GaAs/AlAs Microcavity for Subterahertz Phonons and Near-Infrared Light
We show that distributed Bragg reflector GaAs/AlAs vertical cavities designed to confine photons are automatically optimal to confine phonons of the same wavelength, strongly enhancing their interaction. We study the impulsive generation of intense coherent and monochromatic acoustic phonons by following the time evolution of the elastic strain in picosecond-laser experiments. Efficient optical detection is assured by the strong phonon backaction on the high-Q optical cavity mode. Large optomechanical factors are reported (similar to THz/nm range). Pillar cavities based in these structures are predicted to display picogram effective masses, almost perfect sound extraction, and threshold powers for the stimulated emission of phonons in the range mu W-mW, opening the way for the demonstration of phonon "lasing" by parametric instability in these devices.Fil: Fainstein, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Lanzillotti Kimura, N. D.. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Jusserand, B.. Universite de Paris Vi. Institut Des Nanosciences de Paris; Francia. Centre National de la Recherche Scientifique; Francia. Universite Pierre et Marie Curie; FranciaFil: Perrin, B.. Universite de Paris Vi. Institut Des Nanosciences de Paris; Franci
Topological acoustics in coupled nanocavity arrays
The Su-Schrieffer-Heeger (SSH) model is likely the simplest one-dimensional
concept to study non-trivial topological phases and topological excitations.
Originally developed to explain the electric conductivity of polyacetylene, it
has become a platform for the study of topological effects in electronics,
photonics and ultra-cold atomic systems. Here, we propose an experimentally
feasible implementation of the SSH model based on coupled one-dimensional
acoustic nanoresonators working in the GHz-THz range. In this simulator it is
possible to implement different signs in the nearest neighbor interaction
terms, showing full tunability of all parameters in the SSH model. Based on
this concept we construct topological transition points generating nanophononic
edge and interface states and propose an easy scheme to experimentally probe
their spatial complex amplitude distribution directly by well-established
optical pump-probe techniques.Comment: 10 pages, 4 figure
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
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