Inverted pin beams for robust long-range propagation through atmospheric turbulence.

We introduce a new, to the best of our knowledge, class of optical beams, which feature a spatial profile akin to an "inverted pin." In particular, we asymptotically find that close to the axis, the transverse amplitude profile of such beams takes the form of a Bessel function with a width that gradually increases during propagation. We examine numerically the behavior of such inverted pin beams in turbulent environments as measured via the scintillation index and show that they outperform Gaussian beams (collimated and focused) as well as Bessel beams and regular pin beams, which are all optimized, especially in the moderate and strong fluctuation regimes.

Optical vortices shape optical tornados.

We demonstrate that by seeding an accelerating ring-Airy beam with a finite number of off-axis optical vortices, it transforms into a tornado wave (ToW) upon propagation. Using numerical simulations, we show that both the spiraling high-intensity lobes and the optical vortices exhibit angular acceleration and follow interwinding braid-like trajectories. Likewise, we study the effect of the number, position, and topological charge of the vortices on the propagation dynamics and reveal the connection between optical vortices and optical tornados.

Red Blood Cell-Conditioned Media from Non-Alcoholic Fatty Liver Disease Patients Contain Increased MCP1 and Induce TNF-α Release.

Background: Non-alcoholic fatty liver disease (NAFLD) constitutes a global pandemic. An intricate network among cytokines and lipids possesses a central role in NAFLD pathogenesis. Red blood cells comprise an important source of both cytokines and signaling lipids and have an important role in molecular crosstalk during immunometabolic deregulation. However, their role in NAFLD has not been thoroughly investigated. Methods: Conditioned media from erythrocytes derived from 10 NAFLD patients (4 men, 6 women, aged 57.875±15.16) and 10 healthy controls (4 men, 6 women, aged 39.3±15.55) was analyzed for the cytokines IFN-γ, TNF-α, CCL2, CCL5, IL-8, IL-1ß, IL-12p40, IL-17, MIP-1ß, the signaling lipids sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA), and cholesterol. Their effect on the cytokine profile released by RAW 264.7 macrophages was also studied. Results: MCP1 levels were greater in conditioned growth medium from NAFLD patient erythrocytes than in that from healthy controls (37±40 vs 6.51±5.63 pg/ml). No statistically significant differences were found between patients and healthy controls with regard to S1P, LPA, cholesterol, or eight other cytokines. TNF-a release by RAW 264.7 cells was greater after incubation with patient-derived erythrocyte-conditioned medium than in medium without RAW 264.7 cells from either healthy or NAFLD subjects. Conclusion: Erythrocytes may contribute to liver infiltration by monocytes, and macrophage activation, partially due to CCL2 release, in the context of NAFLD..

Terahertz emission from curved plasma filaments induced by two-color 2D Airy wave packets.

We experimentally demonstrate that 2D Airy wave packets can produce intense curved two-color filaments that emit terahertz (THz) radiation with unique characteristics. Due to the curvature of the plasma channel, THz waves, emitted from different longitudinal regions of the plasma, propagate in different directions resulting in non-concentric THz cones in the far-field. These cones have different cone angles and polarization which we attribute to the way the two-color 2D Airy driving fields are produced in the nonlinear crystal and then propagate to form the curved plasma filament.

Ultra-broadband tunable continuous phase masks using optical aberrations: publisher's note.

This publisher's note corrects errors in Eq. (2) of Opt. Lett.43, 5480 (2018)OPLEDP0146-959210.1364/OL.43.005480.

Ultra-broadband tunable continuous phase masks using optical aberrations.

We show that through the use of optical aberrations, a reflective cylindrical beam expander can be properly adjusted to perform as a tunable ultra-broadband continuous phase modulation device. We demonstrate the effectiveness of such a device for the case of a net cubic phase modulation that is used to generate ultra-broadband white light 2D Airy beams. In this case, the nature of our device enables all spectral components to copropagate, following the same accelerating trajectory. The scalability of our approach, both in respect of input power and bandwidth, makes it possible to be used in any part of the electromagnetic spectrum.

Simple precision measurements of optical beam sizes.

We present a simple high-precision method to quickly and accurately measure the diameters of Gaussian beams, Airy spots, and central peaks of Bessel beams ranging from sub-millimeter to many centimeters without specialized equipment. By simply moving a wire through the beam and recording the relative losses using an optical power meter, one can easily measure the beam diameters with a precision of 1%. The accuracy of this method has been experimentally verified for Gaussian beams down to the limit of a commercial slit-based beam profiler (3%).

Phase Memory Preserving Harmonics from Abruptly Autofocusing Beams.

We demonstrate both theoretically and experimentally that the harmonics from abruptly autofocusing ring-Airy beams present a surprising property: They preserve the phase distribution of the fundamental beam. Consequently, this "phase memory" imparts to the harmonics the abrupt autofocusing behavior, while, under certain conditions, their foci coincide in space with the one of the fundamental. Experiments agree well with our theoretical estimates and detailed numerical calculations. Our findings open the way for the use of such beams and their harmonics in strong field science.

Janus waves.

We show the existence of a family of waves that share a common interesting property affecting the way these waves propagate and focus. The waves are a superposition of twin waves, which are conjugate to each other under inversion of the propagation direction. In analogy to holography, these twin "real" and "virtual" waves are related, respectively, to the converging and diverging parts of the beam and can be clearly visualized in real space at two distinct foci under the action of a focusing lens. Analytic formulas for the intensity distribution after focusing are derived, while numerical and experimental demonstrations are given for some of the most interesting members of this family, the accelerating Airy and ring-Airy beams.

Off-resonance and non-resonant dispersion of Kerr nonlinearity for symmetric molecules [Invited].

The exact formula is derived from the "sum over states" (SOS) quantum mechanical model for the frequency dispersion of the nonlinear refractive index coefficient n2 for centrosymmetric molecules in the off-resonance and non-resonant regimes. This expression is characterized by interference between terms from two-photon transitions from the ground state to the even-symmetry excited states and one-photon transitions between the ground state and odd-symmetry excited states. When contributions from the two-photon terms exceed those from the one-photon terms, the non-resonant intensity-dependent refractive index n2>0, and vice versa. Examples of the frequency dispersion for the three-level SOS model are given. Comparison is made with other existing theories.

Nonlinear birefringence due to non-resonant, higher-order Kerr effect in isotropic media.

The recent interpretation of experiments on the nonlinear non-resonant birefringence induced in a weak probe beam by a high intensity pump beam in air and its constituents has stimulated interest in the non-resonant birefringence due to higher-order Kerr nonlinearities. Here a simple formalism is invoked to determine the non-resonant birefringence for higher-order Kerr coefficients. Some general relations between nonlinear coefficients with arbitrary frequency inputs are also derived for isotropic media. It is shown that the previous linear extrapolations for higher-order birefringence (based on literature values of n2 and n4) are not strictly valid, although the errors introduced in the values of the reported higher- order Kerr coefficients are a few percent.

A prospective study of acute poisonings in a sample of Greek patients.

OBJECTIVES: Acute poisoning is one of the most common situations managed in the emergency department. Significant differences have been reported concerning the prevalence and etiology of poisoning. This study aims to present the epidemiologic and clinical characteristics of poisonings in the region of Thrace in Northern Greece, where no similar studies have been performed. METHODS: A prospective study was carried out in our hospital's emergency department during 4 years (1999-2003). Atotal of 223 adult patients were admitted with acute poisoning, 87 males (39%) and 136 females (61%). RESULTS: Mean age of male and female patients was 37.1 years (standard deviation 16.1) and 33.4 years (standard deviation 14.5), respectively. Intoxications were more common in summer (34.1%). The median time between poisoning and presentation was 4 hours. Poisonings were more common in the urban population (64.1%). Psychotropes were the leading cause of poisoning in patients with a psychiatric disease (74.1%) and analgesics in all the other patients groups (34.8%). The clinical status on admission was: conscious (45.7%), confused (35.4%), precoma/coma (18.9%). Haemodialysis was performed only in one patient and respiratory support was necessary in 10 patients. An antidote was administrated in 73 patients. Median hospital stay was 1 day. Two patients died (0.9%). CONCLUSIONS: Poisoning's aetiology varies significantly in different countries. Previous suicide attempts are common in these patients. Precipitating factors can be major depressive, or dysthymic disorders. The mortality rate is low.

Longitudinal coherence of organic-based microcavity lasers.

We report on the measurement of the longitudinal coherence of organic microcavity lasers based on a conjugated polymer. By using a modified Michelson interferometer configuration enabling single-shot measurements of the coherence length, the transition from spontaneous emission to lasing is investigated. The measured coherence length grows upon increasing the pumping fluence, saturating around 45 microm above threshold. At large fluences, possible thermal and photo-oxidation processes occurring in the gain medium limit the further increase of the coherence length. Our results are important for understanding lasing emission in organic microcavities and optimizing the device design and performances.

Ultrashort laser pulse filamentation from spontaneous X-Wave formation in air.

The description of ultrashort laser pulse filamentation in condensed media as a spontaneous formation of X waves is shown to apply also to filaments generated in air. Within this framework, a simple explanation is brought for several features of the filament such as the subdiffractive propagation and the energy flux from the weakly localized tails of the X-waves to the intense core.

Embedded birefringent computer-generated holograms fabricated by femtosecond laser pulses.

Birefringent computer-generated holograms are fabricated in bulk fused silica by tight focusing of infrared femtosecond laser pulses. The polarization properties of the elliptically polarized diffracted light are in excellent agreement with the theoretical model. We experimentally demonstrate that for such birefringent structures the signal-to-noise ratio increases by approximately 9 dB when polarization filtering is used to suppress the undiffracted beam.

Holographic read - write projector of video images.

We demonstrate two real-time, read-write holographic projectors of video images based on photorefractive materials. A photorefractive crystal holographically records multiple, angularly multiplexed 2D images. By sequentially reconstructing each pre-recorded image a holographic video is created. In first setup the 2D image of an LCD screen is holographicaly recorded in a photorefractive LiNbO3 crystal. In the second setup the Fourier transform of the LCD screen is recoded in the crystal. A detailed comparison of the two setups along with a number of videos is provided. The Fourier transform recording is superior in image quality compared to the direct image recording.