arXiv subjects

Pierre Etienne Allain

Publications and source records attributed to Pierre Etienne Allain.

5 recordsLinked to original sources

arXiv2025

Bayesian approach for spatial super-resolution of heterodyne wind lidars

Wind speed measurements using heterodyne lidars are limited in spatial resolution because of the current signal processing methods. This limit is equal to c $τ$ ( c is the speed of light and $τ$ is the laser pulse duration) corresponding to the length of the atmosphere contributing to the wind speed measurement at one distance. To go beyond this limit, we use an inverse problem approach based on a model of the spectrogram (concatenation of periodograms of each range) and prior distributions on our unknowns: backscattering amplitude and wind speed at each range. We apply our inversion method to simulated and experimental spectrograms, demonstrating a gain in resolution by a factor of 2 to 2.5 depending on the signal-to-noise ratio.

physics.ins-det↗

arXiv2021

A multiphysics model for high frequency optomechanical sensors optically actuated and detected in the oscillating mode

Optomechanical systems combine extreme sensitivity and bandwidth in the control of mechanical motion, of interest for various applications. Integrated on a chip, actuated and detected all-optically by a single laser, they could disrupt sensing technologies. We introduce here a multiphysics model that describes their operation in the oscillating mode, under sinusoidal modulation of the laser, when both photothermal forces and radiation pressure are present, and when nonlinear absorption occurs in the device. The model is validated by systematic experiments on ultra-high frequency optomechanical disk resonators and leads to a quantitative assessment of the amplitude and phase of the demodulated output signal, which carries the sensing information.

physics.optics↗

arXiv2018

Optomechanical Resonating Probe for Very High Speed Sensing of Atomic Forces

Atomic force spectroscopy and microscopy (AFM) are invaluable tools to characterize nanostructures and biological systems. Most experiments, including state-of-the-art images of molecular bonds, are achieved by driving probes at their mechanical resonance. This resonance reaches the MHz for the fastest AFM micro-cantilevers, with typical motion amplitude of a few nanometres. Next-generation investigations of molecular scale dynamics, including faster force imaging and higher-resolution spectroscopy of dissipative interactions, require more bandwidth and vibration amplitudes below interatomic distance, for non-perturbative short-range tip-matter interactions. Probe frequency is a key parameter to improve bandwidth while reducing Brownian motion, allowing large signal-to-noise for exquisite resolution. Optomechanical resonators reach motion detection at 10^(-18) m.(Hz)^(-1/2), while coupling light to bulk vibration modes whose frequencies largely surpass those of cantilevers. Here we introduce an optically operated resonating optomechanical atomic force probe of frequency 2 decades above the fastest functional AFM cantilevers while Brownian motion is 4 orders below. Based on a Silicon-On-Insulator technology, the probe demonstrates high-speed sensing of contact and non-contact interactions with sub-picometre driven motion, breaking open current locks for faster and finer atomic force spectroscopy.

physics.ins-det↗

arXiv2018

Microscopic nanomechanical dissipation in gallium arsenide resonators

We report on a systematic study of nanomechanical dissipation in high-frequency (approximatively 300 MHz) gallium arsenide optomechanical disk resonators, in conditions where clamping and fluidic losses are negligible. Phonon-phonon interactions are shown to contribute with a loss background fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina at the surface modifies the quality factor of resonators, pointing towards the importance of surface dissipation. The temperature evolution is accurately fitted by two-level systems models, showing that nanomechanical dissipation in gallium arsenide resonators directly connects to their microscopic properties. Two-level systems, notably at surfaces, appear to rule the damping and fluctuations of such high-quality crystalline nanomechanical devices, at all temperatures from 3 to 300K.

cond-mat.mes-hall↗

arXiv2016

Color Atomic Force Microscopy with on-the-fly Morse parameters mapping

Atomic Force Microscopy has enabled 2D imaging at the sub-molecular level, and 3D mapping of the potential field. However, fast identification of the surface still remains a challenging topic. In this paper, as a step towards implementation of such function, we introduce a control scheme and mathematical treatment of the acquired data that enable retrieval of essential information characterizing the potential field, leading to fast acquisition of images with chemical contrast. The control scheme is based on tip sample distance modulation at an angular frequency of $ω$, and null control of the ${1ω}$ component of the self excitation frequency of the oscillator. It is demonstrated that the control is robust in UHV for a frequency well as small as a few Hz/MHz, and that the mathematical treatment results in satisfactory identification of the potential field. Morse potential is chosen as a case study for identifying the Morse parameters per pixel. Atomic features with similar topography were distinguished by differences in the parameters. The decay length parameter was resolved with a resolution of 10 pm. The method was demonstrated on quenched Silicon at a scan rate comparable to normal imaging.

cond-mat.mes-hall↗