Abstract
This paper discusses the calculation of the trapping forces in optical tweezers using a combination of the finite differences time domain (FDTD) method and the Lorentz force on electric dipoles. The results of 2D simulations of the trapping of a circular particle by a waveguide with a circular tip are presented and discussed. © 2012 The Author(s).

Abstract
This work presents numerical results related to an in-line Mach-Zehnder interferometer used as a refractive index sensor. The in-line Mach-Zehnder is based on abrupt tapers in standard single mode optical fiber. Numerical simulations were carried out using commercial software based on Beam Propagation Method in order to analyze the sensitivity response in terms of wavelength shift when this sensor is bent at certain radii of curvature. We realized that application of bending in the In-line Mach-Zehnder interferometer enhanced considerably the sensitivity of this sensor to the external refractive index. The best result was achieved for a radius of curvature of 10 mm (similar to 500 nm/RIU for the refractive index range of 1.33 to 1.41) improving the sensitivity about eight times in comparison with the case with no bent.

Abstract
A Long Period Grating (LPG)-based platform for the detection of E. coli outer membranes proteins (EcOMPs) is presented. The sensing probe is achieved by the functionalization of a LPG inscribed in a single mode fiber (SMF28) with a DNA-aptamer resulting in a label-free configuration capable of specific recognize EcOMPs in waters. Measurement takes place by tracking the variations induced in the resonance wavelength by the refractive index changes at the fiber surface (approximate to 100 nm/RIU). The sensing head was characterized and tested against EcOMPs and applied to spiked environmental water samples. The sensor displayed logarithmic responses in the range of 0.1 nM to 10 nM EcOMPs and is regenerated (under low pH conditions) and the deviation of the subsequent detection was less than 0.1%.

Abstract
A fiber optic sensor based on a long-period grating (LPG) inscribed in a photonic crystal fiber is investigated for vibration sensing for structural monitoring applications. In this paper, preliminary results are shown demonstrating the sensor ability to detect vibration induced in a test structure. The sensor frequency response when attached to a loudspeaker-acrylic plate stimulation system (tested in the range from 40 Hz to 2.5 kHz) is analyzed using an intensity based scheme with a tunable laser. An alternative interrogation scheme, where the vibration signal is retrieved from a spectral scan, is also demonstrated and analyzed showing promising characteristics for structural health monitoring.

Abstract
A Fabry-Perot microcavity tip temperature sensor based on a special design double-cladding optical fiber is proposed. The produced fiber has pure silica core and outer cladding and a silica ring doped with phosphorous. The whole ring region is removed by chemical etching post-processing. Consequently, light will be guided in the core region. In a first step, the double-cladding optical fiber is spliced to single mode fiber. Afterwards, the tip is etched in a solution of 48% hydrofluoric acid. The inner cladding will be etched faster, and the core becomes suspended and surrounded by air. The Fabry-Perot microcavity tip sensor is subjected to temperature, and a linear sensitivity of 14.6 pm/degrees C is obtained.

Abstract
To determine the differences between the optical clearing effects created by ethylene glycol in fresh and frozen samples, we have performed several measurements from samples in both conditions. Fresh samples were used after animal sacrifice and frozen samples were kept at -20 degrees C for 72 hours. The different measurements performed with samples from both cases were total transmittance, collimated transmittance, total reflectance and specular reflectance. Considering, for instance, collimated transmittance measurements, we have verified that the spectra measured from both samples before adding the solution present different levels of collimated transmittance. The time-dependence evolution of the collimated transmittance spectrum is similar between both cases of samples, but since they present different levels of "natural" transmittance, the optical clearing effect is observed at different levels if we compare between fresh and frozen samples.