We demonstrate a $16{\mathrm{m}}^2$ helium-neon ring laser gyroscope with sufficient sensitivity and stability to directly detect the Chandler wobble of the rotating Earth. The successful detection of both the Chandler and the annual wobble is verified by comparing the time series of the ring laser measurements against the “C04 series” of Earth rotation data from the International Earth Rotation and Reference System Service.

We study the formation of localized structures formed by the point loading of an internally pressurized elastic shell. While unpressurized shells (such as a ping-pong ball) buckle into polygonal structures, we show that pressurized shells are subject to a wrinkling instability. We study wrinkling in depth, presenting scaling laws for the critical indentation at which wrinkling occurs and the number of wrinkles formed in terms of the internal pressurization and material properties of the shell. These results are validated by numerical simulations. We show that the evolution of the wrinkle length with increasing indentation can be understood for highly pressurized shells from membrane theory. These results suggest that the position and number of wrinkles may be used in combination to give simple methods for the estimation of the mechanical properties of highly pressurized shells.

Coherent Rayleigh-Brillouin scattering is a four-wave mixing technique that provides information on various physical properties of the scattering medium in the spectral domain. Being based on density gratings generated by dipole forces, the method requires two pump beams of sufficient spectral width to span the full response bandwidth of the scattering medium. We provide experimental data on the scattered spectrum as a function of the coherence between the two pump beams and derive the corresponding pump beam spectrum. We argue that all experiments on coherent Rayleigh-Brillouin scattering to date, have, in fact, been performed in the incoherent regime and show that orders of magnitude in scattering efficiency are to be expected when the experiments are performed with bandwidth-limited picosecond laser pulses.

Transformation optics is a design tool that connects the geometry of space and propagation of light. Invisibility cloaking is a corresponding benchmark example. Recent experiments at optical frequencies have demonstrated cloaking for the light amplitude only. In this Letter, we demonstrate far-field cloaking of the light phase by interferometric microscope-imaging experiments on the previously introduced three-dimensional carpet cloak at 700 nm wavelength and for arbitrary polarization of light.

A single-photon optical diode operates on individual photons and allows unidirectional propagation of photons. By exploiting the unique polarization configuration in a waveguide, we show here that a single-photon optical diode can be accomplished by coupling a quantum impurity to a passive, linear optical waveguide which possesses a locally planar, circular polarization. We further show that the diode provides a near unitary contrast for an input pulse with finite frequency bandwidth and can be implemented in a variety of types of waveguides. Moreover, the performance of the diode is not sensitive to the intrinsic dissipation of the quantum impurity.

We have fabricated and characterized a novel superhydrophobic system, a meshlike porous superhydrophobic membrane with solid area fraction ${\Phi }_s$, which can maintain intimate contact with outside air and water reservoirs simultaneously. Oscillatory hydrodynamic measurements on porous superhydrophobic membranes as a function of ${\Phi }_s$ reveal surprising effects. The hydrodynamic mass oscillating in phase with the membranes stays constant for $0.9\lesssim {\Phi }_s\le 1$, but drops precipitously for ${\Phi }_s<0.9$. The viscous friction shows a similar drop after a slow initial decrease proportional to ${\Phi }_s$. We attribute these effects to the percolation of a stable Knudsen layer of air at the interface.

We inquire about the properties of 2D Navier-Stokes turbulence simultaneously forced at small and large scales. The background motivation comes by observational results on atmospheric turbulence. We show that the velocity field is amenable to the sum of two auxiliary velocity fields forced at large and small scale and exhibiting a direct enstrophy and an inverse-energy cascade, respectively. Remarkably, the two auxiliary fields reconcile universal properties of fluxes with positive statistical correlation in the inertial range.

The local kinetic energy dissipation rate ${ϵ}_{u,c}$ in Rayleigh-Bénard convection cell was measured experimentally using the particle tracking velocimetry method, with varying Rayleigh number Ra, Prandtl number Pr, and cell height $H$. It is found that ${ϵ}_{u,c}/({\kappa }^3{H}^{-4})=1.05\times {10}^{-4}{\mathrm{Ra}}^{1.55\pm 0.02}{\mathrm{Pr}}^{1.15\pm 0.38}$. The Ra and $H$ dependencies of the measured results are found to be consistent with the assumption made for the bulk energy dissipation rate ${ϵ}_{u,\mathrm{bulk}}$ in the Grossmann-Lohse model. A remarkable finding of the study is that ${ϵ}_{u,c}$ balances the directly measured local Nusselt number ${\mathrm{Nu}}_c$ in the cell center, not only scalingwise but also in magnitude.

The present study investigates the spatiotemporal variability in the dynamics of self-sustained supersonic reaction waves propagating through an excitable medium. The model is an extension of Fickett’s detonation model with a state-dependent energy addition term. Stable and pulsating supersonic waves are predicted. With increasing sensitivity of the reaction rate, the reaction wave transits from steady propagation to stable limit cycles and eventually to chaos through the classical Feigenbaum route. The physical pulsation mechanism is explained by the coherence between internal wave motion and energy release. The results obtained clarify the physical origin of detonation wave instability in chemical detonations previously observed experimentally.

Enhancing and funneling light efficiently through deep subwavelength apertures is essential in harnessing light-matter interaction. Thus far, this has been accomplished resonantly, by exciting the structural surface plasmons of perforated nanostructured metal films, a phenomenon known as extraordinary optical transmission. Here, we present a new paradigm structure which possesses all the capabilities of extraordinary optical transmission platforms, yet operates nonresonantly on a distinctly different mechanism. Our proposed platform demonstrates efficient ultrabroadband funneling of optical power confined in an area as small as $\sim (\frac{\lambda }{500}{)}^2$, where optical fields are enhanced, thus exhibiting functional possibilities beyond resonant platforms. We analyze the nonresonant mechanism underpinning such a phenomenon with a simple quasistatic picture, which shows excellent agreement with our numerical simulations.

We show that thermal creep is at the origin of the recently discovered Leidenfrost ratchet, where liquid droplets float on a vapor layer along a heated sawtooth surface and accelerate to velocities of up to $40\mathrm{cm}/\mathrm{s}$. As the active element, the asymmetric temperature profile at each ratchet summit rectifies the vapor flow in the boundary layer. This mechanism works at low Reynolds number and provides a novel tool for controlling gas flow at nanostructured surfaces.

We show that a weakly absorbing, strongly scattering (white) medium can be made very strongly absorbing at any frequency within its strong-scattering bandwidth by optimizing the input electromagnetic field. For uniform absorption, results from random matrix theory imply that the reflectivity of the medium can be suppressed by a factor $\sim ({\ell }_a/\ell )N^{-2}$, where $N$ is the number of incident channels and $\ell$, ${\ell }_a$ are the elastic and absorption mean free paths, respectively. It is thus possible to increase absorption from a few percent to $>99\%$. For a localized weak absorber buried in a nonabsorbing scattering medium, we find a large but bounded enhancement.

Flaps can be detached from a thin film glued on a solid substrate by tearing and peeling. For flat substrates, it has been shown that these flaps spontaneously narrow and collapse in pointy triangular shapes. Here we show that various shapes, triangular, elliptic, acuminate, or spatulate, can be observed for the tears by adjusting the curvature of the substrate. From combined experiments and theoretical models, we show that the flap morphology is governed by simple geometric rules.

By treating idealized zeolite frameworks as periodic mechanical trusses, we show that the number of flexible folding mechanisms in zeolite frameworks is strongly peaked at the minimum density end of their flexibility window. 25 of the 197 known zeolite frameworks exhibit an extensive flexibility, where the number of unique mechanisms increases linearly with the volume when long wavelength mechanisms are included. Extensively flexible frameworks therefore have a maximum in configurational entropy, as large crystals, at their lowest density. Most real zeolites do not exhibit extensive flexibility, suggesting that surface and edge mechanisms are important, likely during the nucleation and growth stage. The prevalence of flexibility in real zeolites suggests that, in addition to low framework energy, it is an important criterion when searching large databases of hypothetical zeolites for potentially useful realizable structures.

Modulations of the friction force in dry solid friction are usually attributed to macroscopic stick-slip instabilities. Here we show that a distinct, quasistatic mechanism can also lead to nearly periodic force oscillations during sliding contact between an elastomer patterned with parallel grooves, and abraded glass slides. The dominant oscillation frequency is set by the ratio between the sliding velocity and the grooves period. A model is derived which quantitatively captures the dependence of the force modulations amplitude with the normal load, the grooves period, and the slides roughness characteristics. The model’s main ingredient is the nonlinearity of the friction law. Since such nonlinearity is ubiquitous for soft solids, this “fingerprint effect” should be relevant to a large class of frictional configurations and have important consequences in human digital touch.

The apparently intractable shape of a fold in a compressed elastic film lying on a fluid substrate is found to have an exact solution. Such systems buckle at a nonzero wave vector set by the bending stiffness of the film and the weight of the substrate fluid. Our solution describes the entire progression from a weakly displaced sinusoidal buckling to a single large fold that contacts itself. The pressure decrease is exactly quadratic in the lateral displacement. We identify a complex wave vector whose magnitude remains invariant with compression.

We study the slippage of a gas along mobile rigid walls in the sphere-plane confined geometry and find that it varies considerably with pressure. The classical no-slip boundary condition valid at ambient pressure changes continuously to an almost perfect slip condition in a primary vacuum. Our study emphasizes the key role played by the mean free path of the gas molecules on the interaction between a confined fluid and solid surfaces and further demonstrates that the macroscopic hydrodynamics approach can be used with confidence even in a primary vacuum environment where it is intuitively expected to fail.

We demonstrate control of short and long quantum trajectories in high harmonic emission through the use of an orthogonally polarized two-color field. By controlling the relative phase $\varphi$ between the two fields we show via classical and quantum calculations that we can steer the two-dimensional trajectories to return, or not, to the core and so control the relative strength of the short or long quantum trajectory contribution. In experiments, we demonstrate that this leads to robust control over the trajectory contributions using a drive field from a femtosecond laser composed of the fundamental $\omega$ at 800 nm (intensity $\sim 1.2\times {10}^{14}\mathrm{W}{\mathrm{cm}}^{-2}$) and its weaker orthogonally polarized second harmonic $2\omega$ (intensity $\sim 0.3\times {10}^{14}\mathrm{W}{\mathrm{cm}}^{-2}$) with the relative phase between the $\omega$ and $2\omega$ fields varied simply by tilting a fused silica plate. This is the first demonstration of short and long quantum trajectory control at the single-atom level.

It is widely accepted that, on ensemble average, the transmission $T$ of guided modes decays exponentially with the waveguide length $L$ due to small imperfections, leading to the important figure of merit defined as the attenuation-rate coefficient $\alpha =-⟨\ln (T)⟩/L$. In this Letter, we evidence that the exponential-damping law is not valid in general for periodic monomode waveguides, especially as the group velocity decreases. This result, that contradicts common beliefs and experimental practices aiming at measuring $\alpha$, is supported by a theoretical study of light transport in the limit of very small imperfections, and by numerical results obtained for two waveguide geometries that offer contrasted damping behaviors.

The traditional viewpoint of fluid flow considers the transition to turbulence to occur by the secondary and nonlinear instability of wave packets, which have been created experimentally by localized harmonic excitation. The boundary layer has been shown theoretically to support spatiotemporal growing wave fronts by Sengupta, Rao, and Venkatasubbaiah [Phys. Rev. Lett. 96, 224504 (2006)] by a linear mechanism, which is shown here to grow continuously, causing the transition to turbulence. Here, we track spatiotemporal wave fronts to a nonlinear turbulent state by solving the full 2D Navier-Stokes equation, without any limiting assumptions. Thus, this is the only demonstration of deterministic disturbances evolving from a receptivity stage to the full turbulent flow. This is despite the prevalent competing conjectures of the event being three-dimensional and/or stochastic in nature.