Cavity Optomechanics with a Polymer Coated Nanomembrane

The emerging fields of cavity optomechanics explores the interaction between electromagnetic radiation and nano or micromechanical motion. The variety of experimental systems and possible applications range from gravitational-wave interferometry to the experimental demonstration of the quantum ground state of a mechanical resonator, from ultrasensitive measurement to fundamental questions in quantum physics. Optomechanical interaction are mediated by radiation pressure or photothermal forces. In our experiment we focused on the latter in the case of a Fabry-Pérot hemiconfocal cavity, where the plain mirror of the cavity was a polymer coated nanomembrane. Starting from the build up and configuration of the whole apparatus, we have been studying the bolometric effect for two different laser wavelengths, that is for two different absorption rates of the polymer, as well as the transmission and reflection properties of the membrane. Working in the high vacuum regime we moved on to the study of the actual optomechanical phenomena: we have been able to observe cooling effects on the first normal mode of the membrane and we have studied the dynamics of nonlinear effects typical of a slow-fast systems

Alq3 coated silicon nanomembranes for cavity optomechanics

The optomechanical properties of a silicon-nitride membrane mirror covered by Alq3 and Silver layers are investigated. Excitation at two laser wavelengths, 780 and 405 nm, corresponding to different absorptions of the multilayer, is examined. Such dual driving will lead to a more flexible optomechanical operation. Topographic reconstruction of the whole static membrane deformation and cooling of the membrane oscillations are reported. The cooling, observed for blue laser detuning and produced by bolometric forces, is deduced from the optomechanical damping of the membrane eigenfrequency. We determine the presence of different contributions to the photothermal response of the membrane

Cavity nano-optomechanics in the ultrastrong coupling regime with ultrasensitive force sensors

In a canonical optomechanical system, mechanical vibrations are dynamically encoded on an optical probe field which reciprocally exerts a backaction force. Due to the weak single photon coupling strength achieved with macroscopic oscillators, most of existing experiments were conducted with large photon numbers to achieve sizeable effects, thereby causing a dilution of the original optomechanical non-linearity. Here, we investigate the optomechanical interaction of an ultrasensi-tive suspended nanowire inserted in a fiber-based microcavity mode. This implementation allows to enter far into the hitherto unexplored ultrastrong optomechanical coupling regime, where one single intracavity photon can displace the oscillator by more than its zero point fluctuations. To fully characterize our system, we implement nanowire-based scanning probe measurements to map the vectorial optomechanical coupling strength, but also to reveal the intracavity optomechanical force field experienced by the nanowire. This work establishes that the single photon cavity optomechanics regime is within experimental reach. Introduction-The field of optomechanics has gone through many impressive developments over the last decades [1]. The coupling between a probe light field and a mechanical degree of freedom, an oscillator, possibly assisted by a high finesse cavity was early proposed as an ideal platform to explore the quantum limits of ultrasen-sitive measurements, where the quantum fluctuations of the light are the dominant source of measurement noise [2-5]. The measurement backaction was also employed to manipulate the oscillator state through optical forces and dynamical backaction, leading to optomechanical correlations between both components of the system. In this framework, ground state cooling, mechanical detection of radiation pressure quantum noise, advanced correlation between light and mechanical states or optomechanical squeezing were reported [6-19]. All those impressive results were obtained in the linear regime of cavity optomechanics, making use of large photon numbers, where the interaction Hamiltonian is linearized around an operating setpoint. However, the optomechanical interaction possesses an intrinsic non-linearity at the single excitation level, which has for the moment remained far from experimental reach due to the weak single photon coupling strength achieved with macroscopic oscillators. This regime is achieved when a single photon in the cavity shifts the static rest position of the mechanical resonator by a quantity δx (1) which is larger than its zero point fluctuations δx zpf. A very strong optomechanical interaction is indeed needed to fulfil this condition since it requires g 0 /Ω m > 1 where g 0 is the single photon optomechanical coupling and Ω m the resonant pulsation of the mechanical oscillator. Operating in the ultra-strong coupling regime is thus an experimenta

Ultrasensitive nano-optomechanical force sensor at dilution temperatures

Cooling down nanomechanical force probes is a generic strategy to enhance their sensitivities through the concomitant reduction of their thermal noise and mechanical damping rates. However, heat conduction mechanisms become less efficient at low temperatures, which renders difficult to ensure and verify their proper thermalization. To operate with minimally perturbing measurements, we implement optomechanical readout techniques operating in the photon counting regime to probe the dynamics of suspended silicon carbide nanowires in a dilution refrigerator. Readout of their vibrations is realized with sub-picowatt optical powers, in a regime where less than one photon is collected per oscillation period. We demonstrate their thermalization down to $32\pm2$ mK and report on record sensitivities for scanning probe force sensors, at the $40\,\rm zN/Hz^{1/2}$ level, with a sensitivity to lateral force field gradients in the fN/m range. This work opens the road toward nanomechanical vectorial imaging of faint forces at dilution temperatures, at minimal excitation levels

The ultra-processed foods hypothesis: a product processed well beyond the basic ingredients in the package

The NOVA classification of food items has become increasingly popular and is being used in several observational studies as well as in nutritional guidelines and recommendations. We propose that there is a need for this classification and its use in the formulation of public health policies to be critically discussed and re-appraised. The terms "processing" and "ultra-processing," which are crucial to the NOVA classification, are ill-defined, as no scientific, measurable, or precise reference parameters exist for them. Likewise, the theoretical grounds of the NOVA classification are unclear and inaccurate. Overall, the NOVA classification conflicts with the classic, evidence-based evaluation of foods based on composition and portion size because NOVA postulates that the food itself (or how much of it is eaten) are unimportant, but rather that dietary effects are due to how the food is produced. We contend that the NOVA system suffers from a lack of biological plausibility so the assertion that ultra-processed foods are intrinsically unhealthful is largely unproven, and needs further examination and elaboration

Des sondes de force nano-optomécaniques en conditions extrêmes : des ultra-basses températures au régime de couplage ultrafort de l'opto-mécanique en cavité

In recent years nano-optomechanical systems have proven to be a powerful resource to detect ultra-weak forces, thus providing new insights on fundamental interactions. In this work we extend the experimental range of ultrasensitive force measurements based on optically readout vibrations of suspended silicon carbide nanowires to novel experimental regimes: first through operations at dilution temperatures, second in the ultrastrong coupling regime of cavity nano-optomechanics.Operating those force sensors at dilution temperatures permits to reduce their thermal noise and further benefit from an increased mechanical coherence. However this requires eliminating the sources of unwanted vibrations, such as electrical or mechanical noises, and operating at ultralow optical powers to avoid unwanted laser heating. We expose the experimental developments that lead us to observe a nanowire featuring a noise temperature measured at the 32mK level, while exploiting novel optical readout schemes operating in the photon counting regime, where less than a photon is detected per mechanical period. We discuss their mechanical and thermal properties at low temperatures and report on enhanced force sensitivities of a few tens of zN/Hz^1/2, which are sufficient in principle to detect the electron-electron Coulomb interaction over distances larger than 100 µm.In the second part of the manuscript, we describe a novel cavity nano-optomechanical experiment at room temperature that consists in inserting the vibrating extremity of a suspended nanowire with sub-wavelength sized diameter, in a high finesse fiber micro-cavity. The combination of its small mode volume, of the extreme force sensitivity of the nanowires and of the large optomechanical interaction strength demonstrated makes the system very interesting for further explorations of the field of cavity nano-optomechanics. In particular we demonstrate that one can reach the so-called ultrastrong coupling regime, where one single intracavity photon can displace the oscillator by more than its zero point fluctuations. This is achieved when the single photon coupling strength g0 exceeds the mechanical frequency Wm. After having described the experimental platform, we investigate how the nanowire perturbs the intracavity field by mapping the cavity properties as a function of the nanowire position within the standing wave. This permits to quantify and spatially map the optomechanical interaction strength, which acquires a vectorial character. Furthermore we explored the interaction in the reversed direction by mapping the intracavity optical force field experienced by the nanowire and compared our results with dedicated numerical simulations.Implementing this nanowire in the middle optomechanical scheme at low temperatures will permit, by significantly reducing the nanowire thermal noise, to explore the regime of single photon cavity nano-optomechanics. In this regime, particularly interesting for fundamental quantum optics, one single intracavity photon should render the cavity statically bistable and mean field descriptions should not be relevant anymore.Les progrès récents réalisés dans le domaine des systèmes nano-optomécaniques ont démontré leur potentiel pour détecter des forces extrêmement faibles et ouvrir de nouveaux champs d’étude en physique. Ce travail de thèse vise à étendre le champ d’application des mesures de force ultrasensibles basées sur la lecture optique des vibrations de nanofils suspendus à de nouveaux domaines : d’abord à très basse température, en démontrant la possibilité de les exploiter dans un cryostat à dilution, ensuite dans le domaine de la nano-optomécanique en cavité où leur extrême sensibilité permet d’atteindre le régime de couplage ultra-fort.Leur mise en œuvre dans un cryostat à dilution permet en effet de réduire leur bruit thermique tout en bénéficiant d’une augmentation de leur cohérence mécanique mais nécessite de réduire drastiquement les sources de bruits externes, d’origine électrique ou mécanique, tout en opérant à des puissances optiques extrêmement faibles afin de limiter le chauffage par absorption. Nous présentons les développements réalisés, qui nous ont permis d’observer un nanofil présentant une température de bruit de 32 mK grâce à des techniques de mesures fonctionnant en régime de comptage de photon, lorsque moins d’un photon est détecté par période mécanique. Nous étudions les propriétés mécaniques et thermique de ces sondes de force à très basses températures, qui ont permis d’atteindre une sensibilité record pour une sonde locale, de l’ordre de quelques dizaines de zN/Hz^1/2, ce qui est en principe suffisante pour détecteur l’interaction électron-électron à une distance de plus de 100 µm.Dans la seconde partie du manuscrit, on décrit une nouvelle expérience de nano-optomécanique en cavité fonctionnant à température ambiante. Elle consiste à insérer l’extrémité vibrante d’un nanofil suspendu dans une micro-cavité fibrée de grande finesse. La combinaison de son volume de mode très réduit, de la très grande sensibilité en force des nanofils et de l’interaction optomécanique gigantesque obtenue rend cette approche extrêmement intéressante pour la nano-optomécanique en cavité. En effet, on démontre qu’il est possible d’atteindre le régime de couplage ultrafort, dans lequel un seul photon intra-cavité est capable de déplacer le nano-résonateur de plus que ses fluctuations de point zéro. Ceci nécessite d’avoir une constante de couplage par photon g0 dépassant la fréquence mécanique du nanofil Wm. Après avoir décrit l’expérience, on étudie comment le nanofil permet d’imager le champ lumineux intra-cavité en cartographiant ses propriétés optiques en fonction de la position du nanofil de diamètre sub-longueur d’onde dans l’onde stationnaire. Cela permet de quantifier et de cartographier l’intensité et l’orientation de l’interaction optomécanique qui acquiert alors un caractère vectoriel. De plus nous avons étudié l’interaction en sens inverse, en cartographiant le champ de force intra-cavité ressenti par le nanofil en fonction de sa position dans le mode de cavité et comparé nos résultats à des simulations numériques.La mise en œuvre de cette approche optomécanique dite du «nanofil au milieu» à très basse température devrait permettre de réduire suffisamment le bruit thermique des nanofils pour explorer l’optomécanique en cavité au photon unique. Dans ce régime, un seul photon intra-cavité est capable de rendre le système bistable statiquement, ce qui ouvre la voie à des développements nouveaux en optique quantique, ne serait que parce que les théories de champ moyen ne sont alors plus pertinentes

Convenient synthesis of lactuloselysine and its use for LC-MS analysis in milk-like model systems

The synthesis of the Amadori product lactuloselysine [N(ε)(1-deoxy-D- lactulosyl-1)-L-lysine] was obtained starting from FMOC-lysine-OH (N(α)-9- fluorenylmethoxy-carbonyl-N(ε)H2-L-lysine-OH) and lactose. Compound identity was confirmed by MALDI-ToF, electrospray, and NMR analysis. A selective LC-MS procedure which allowed the detection of lactuloselysine up to 10 ng mL-1 was set up and used to follow the formation of the compound in a lactose-lysine model system; quantification of this molecule after complete enzymatic hydrolysis of whey-proteins from milk samples was also performed