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The Airy distribution (AD) describes the probability distribution of the area under a Brownian excursion. The AD is prominent in several areas of physics, mathematics and computer science. Here we use a dilute colloidal system to directly measure, for the first time, the AD in experiment. We also show how two different techniques of theory of large deviations -the Donsker-Varadhan formalism and the optimal fluctuation method -manifest themselves in the AD. We advance the theory of the AD by calculating, at large and small areas, the position distribution of a Brownian excursion conditioned on a given area. For large areas, we uncover two singularities in the large deviation function, which can be interpreted as dynamical phase transitions of third order. For small areas the position distribution coincides with the Ferrari-Spohn distribution, which has previously appeared in other problems, and we identify the reason for this coincidence.

Trapping and manipulation of particles using laser beams has become an important tool in diverse fields of research. In recent years, particular interest is given to the problem of conveying optically trapped particles over extended distances either down or upstream the direction of the photons momentum flow. Here, we propose and demonstrate experimentally an optical analogue of the famous Archimedes' screw where the rotation of a helical-intensity beam is transferred to the axial motion of optically-trapped micro-meter scale airborne carbon based particles. With this optical screw, particles were easily conveyed with controlled velocity and direction, upstream or downstream the optical flow, over a distance of half a centimeter. Our results offer a very simple optical conveyor that could be adapted to a wide range of optical trapping scenarios.

We report the first experimental realization of a rod diffusing in a two dimensional obstacle field following the single rod dynamics. We use a silver nanowire as our rod and two types of obstacles: repelling light beams and polymer pillars. We study the effect of hydrodynamic interactions on the transport of the rod, comparing both experimental realizations and recent simulations. We propose a new framework for analyzing the transport through such systems and predict a new superdiffusive regime of rod transport at high obstacle concentration and short times. [5], and diffusion in porous media. The rich and surprising dynamics emerging from the elongated nature of the diffusive particles render this model interesting also from the perspective of transport theory. For example, at low densities the center-of-mass diffusion decreases with obstacle density, as expected from Enskog theory [6] for spheres. However, above a certain threshold, this trend is reversed and the diffusion coefficient increases with obstacle density. This behavior was predicted theoretically by kinetic theory [7] and demonstrated in simulations [8][9][10] assuming the rod moves ballistically between collisions with obstacles. The increase in diffusion coefficient was predicted to follow a power law of √ n, where n is the obstacle density. In simulations, powers between 0.3-0.8 were reported [9,10]. The aforementioned results apply to an infinitely thin rod, point-like obstacles, and motion in two dimensions. If the rod thickness is finite a new confinement regime [10] appears, and if the rod is allowed to move in three dimensions the enhanced diffusion regime disappears [11].The entire density dependence of the rod center-ofmass diffusion coefficient, D cm , changes if the underlying motion of the rod between collisions is Brownian instead of ballistic [12]. In this case D cm is constant at very low densities and decreases to a lower constant at high densities. The diffusion of a rod at high obstacle densities, both in the case of underlying ballistic motion and diffusive motion is unique for elongated particles. Experimental works on this subject have been few so far, focusing on the motion of elongated objects in dense suspensions rather than through fixed obstacle fields [2,3,13,14]. Recently, a 3D study of the movement of carbon nanotubes in porous agarose was reported focusing on the effect of rod flexibility [15].Here we present the first measurements of single rod dynamics in a static obstacle field. We focus on the short time diffusion of rods and characterize the obstacle density effect on their transport in two different experimental realizations: one with polymer obstacles and one with virtual optical obstacles. We then apply external driving on the rods to induce ballistic-like characteristics to the otherwise Brownian motion of the rods, and finally, we introduce an analysis approach which highlights the effect of the underlying motion type (ballistic or Brownian) on the transport of rods in such systems. Our samples consist of ...

Super-oscillating beams can be used to create light spots whose size is below the diffraction limit with a side ring of high intensity adjacent to them. Optical traps made of the super-oscillating part of such beams exhibit superior localization of submicron beads compared to regular optical traps. Here we focus on the effect of the ratio of particle size to trap size on the localization and stiffness of optical traps made of super-oscillating beams. We find a non-monotonic dependence of trapping stiffness on the ratio of particle size to beam size. Optimal trapping is achieved when the particle is larger than the beam waist of the super-oscillating feature but small enough not to overlap with the side ring. PACS numbers:In the early 70s, Artur Ashkin showed that a weakly focused laser beam can draw small particles with high refractive index towards its center and move them in the direction of light propagation [1]. A major breakthrough in this field happened in 1986 when Ashkin demonstrated the single beam optical gradient force traps [2], known nowadays as optical tweezers. Since then, optical trapping application has become a powerful tool used in physics and biology. However, the size of an optical trap is limited by the smallest spot which collimated light can be focused to using an annular aperture, as discussed in 1873 by Ernst Abbe [3] and later by Lord Rayleigh [4]. The diffraction limit of light determining this minimal beam size is given by w = 0.38λ/NA, where w is the beam waist defined as the full width at half maximum of the beam, λ is the wavelength of the beam, and NA is the numerical aperture of the focusing lens. In 1952 G. Toraldo di Francia suggested theoretically that by phase modulations one can achieve optical features below the diffraction limit [5]. In the 90's the concept of super oscillation (SO) was first introduce by Michel Berry for bandlimited functions that locally oscillate faster than their highest Fourier component [6]. In optics, the SO phenomena was used to generate optical beams with features smaller than the diffraction limit. Over the last 20 years SO beams were generated using different methods [7-9] and applied for super-resolution imaging [10,11].The effect of particle size, beam waist, and wavelength on the stiffness of optical trapping was studied theoretically for different scattering regimes [12][13][14]. Experimental verification of these predictions is challenging since neither beam size, wavelength, nor particle size can be changed continuously to provide a clean comparison [15][16][17][18]. Naturally, all previous measurements focused on diffraction-limited optical traps. Previously, we observed that a significant enhancement of optical trapping strength and localization occurred when a 490 nm particle was trapped in the SO part of a SO beam [19]. Here we study this effect in more detail. We use the unique feature of SO beams, namely, the ability to change continuously the beam waist and to focus the beam to below the diffraction limit, to measure the effect of p...