Speckle filtering through nonlinear wave mixing.

Light scattering by disordered media is a ubiquitous effect. After passing through them, the light acquires a random phase, masking or destroying associated information. Filtering this random phase is of paramount importance to many applications, such as sensing, imaging, and optical communication, to cite a few, and it is commonly achieved through computationally extensive post-processing using statistical correlation. In this work, we show that mixing noisy optical modes of various complexity in a second-order nonlinear medium can be used for efficient and straightforward filtering of a random wavefront under sum-frequency generation processes without utilizing correlation-based calculations.

Suitable state bases for nonlinear optical mode conversion protocols.

By considering parity-defined Laguerre-Gaussian (LG) and Hermite-Gaussian (HG) beams as input modes, we present arguments through experimental and theoretical results in order to affirm that using HG modes as bases is more suitable for optical mode conversion than using LG modes. By analyzing the normalized overlap integral and the generated modes, we determine a clear rule for the dominant mode for nonlinear mixing of HG beams, while the same is not possible for LG beams. In addition, examples of optical modal conversion using both HG and LG modes as input beams are demonstrated.

Probing the reciprocal lattice associated with a triangular slit to determine the orbital angular momentum for a photon.

The orbital angular momentum conservation of light reveals different diffraction patterns univocally dependent on the topological charge of the incident light beam when passing through a triangular aperture. It is demonstrated that these patterns, which are accessed by observing the far-field measurement of the diffracted light, can also be obtained using few photon sources. In order to explain the observed patterns, we introduce an analogy of this optical phenomenon with the study of diffraction for the characterization of the crystal structure of solids. We demonstrate that the finite pattern can be associated with the reciprocal lattice obtained from the direct lattice generated by the primitive vectors composing any two of the sides of the equilateral triangular slit responsible for the diffraction. Using the relation that exists between the direct and reciprocal lattices, we provide a conclusive explanation as to why the diffraction pattern of the main maxima is finite. This can shed a new light on the investigation of crystallographic systems.

Biomechanical and functional properties of trophoblast cells exposed to Group B Streptococcus in vitro and the beneficial effects of uvaol treatment.

BACKGROUND: Group B streptococcus (GBS) is the main bacteria that infects pregnant women and can cause abortion and chorioamnionitis. The impact of GBS effects on human trophoblast cells remains largely elusive, and actions toward anti-inflammatory strategies in pregnancy are needed. A potent anti-inflammatory molecule, uvaol is a triterpene from olive oil and its functions in trophoblasts are unknown. We aimed to analyze biomechanical and functional effects of inactivated GBS in trophoblast cells, with the addition of uvaol to test potential benefits. METHODS: HTR-8/SVneo cells were treated with uvaol and incubated with inactivated GBS. Cell viability and death were analyzed. Cellular elasticity and topography were accessed by atomic force microscopy. Nitrite production was evaluated by Griess reaction. Nuclear translocation of NFkB p65 was detected by immunofluorescence and Th1/Th2 cytokines by bead-based multiplex assay. RESULTS: GBS at 108 CFU increased cell death, which was partially prevented by uvaol. Cell stiffness, cytoskeleton organization and morphology were changed by GBS, and uvaol partially restored these alterations. Nuclear translocation of NFkB p65 began 15 min after GBS incubation and uvaol inhibited this process. GBS decreased IL-4 secretion and increased IL-1ß, IFN-γ and IL-2, whereas uvaol reverted this. CONCLUSIONS: The increased inflammation and cell death caused by GBS correlated with biomechanical and cytoskeleton changes found in trophoblast cells, while uvaol was effective its protective role. GENERAL SIGNIFICANCE: Uvaol is a natural anti-inflammatory product efficient against GBS-induced inflammation and it has potential to be acquired through diet in order to prevent GBS deleterious effects in pregnancy.

Association between biomechanical alterations and migratory ability of semaphorin-3A-treated thymocytes.

BACKGROUND: Class 3 semaphorins are soluble proteins involved in cell adhesion and migration. Semaphorin-3A (Sema3A) was initially shown to be involved in neuronal guidance, and it has also been reported to be associated with immune disorders. Both Sema3A and its receptors are expressed by most immune cells, including monocytes, macrophages, and lymphocytes, and these proteins regulate cell function. Here, we studied the correlation between Sema3A-induced changes in biophysical parameters of thymocytes, and the subsequent repercussions on cell function. METHODS: Thymocytes from mice were treated in vitro with Sema3A for 30min. Scanning electron microscopy was performed to assess cell morphology. Atomic force microscopy was performed to further evaluate cell morphology, membrane roughness, and elasticity. Flow cytometry and/or fluorescence microscopy were performed to assess the F-actin cytoskeleton and ROCK2. Cell adhesion to a bovine serum albumin substrate and transwell migration assays were used to assess cell migration. RESULTS: Sema3A induced filopodia formation in thymocytes, increased membrane stiffness and roughness, and caused a cortical distribution of the cytoskeleton without changes in F-actin levels. Sema3A-treated thymocytes showed reduced substrate adhesion and migratory ability, without changes in cell viability. In addition, Sema3A was able to down-regulate ROCK2. CONCLUSIONS: Sema3A promotes cytoskeletal rearrangement, leading to membrane modifications, including increased stiffness and roughness. This effect in turn affects the adhesion and migration of thymocytes, possibly due to a reduction in ROCK2 expression. GENERAL SIGNIFICANCE: Sema3A treatment impairs thymocyte migration due to biomechanical alterations in cell membranes.

Strong correlations between incoherent vortices.

We establish a correlation rule of which the value of the topological charge obtained in intensity correlation between two coherence vortices is such that this value is bounded by the topological charge of each coherence vortex. The original phase information is scrambled in each speckle pattern and unveiled using numerical intensity correlation. According to this rule, it is also possible to obtain a coherence vortex stable, an integer vortex, even when each incoherent vortex beam is instable, non-integer vortex.

Unveiling a truncated optical lattice associated with a triangular aperture using light's orbital angular momentum.

We show that the orbital angular momentum can be used to unveil lattice properties hidden in diffraction patterns of a simple triangular aperture. Depending on the orbital angular momentum of the incident beam, the far field diffraction pattern reveals a truncated optical lattice associated with the illuminated aperture. This effect can be used to measure the topological charge of light beams.

Nonlinear interferometry via Fock-state projection.

We use a photon-number-resolving detector to monitor the photon-number distribution of the output of an interferometer, as a function of phase delay. As inputs we use coherent states with mean photon number up to seven. The postselection of a specific Fock (photon-number) state effectively induces high-order optical nonlinearities. Following a scheme by Bentley and Boyd [Opt. Express 12, 5735 (2004).10.1364/OPEX.12.005735], we explore this effect to demonstrate interference patterns a factor of 5 smaller than the Rayleigh limit.