Angela Maria Guzman

Sagnac Interferometer Based Generation of Controllable Cylindrical Vector Beams

We report on a novel experimental geometry to generate cylindrical vector beams in a very robust manner. Continuous control of beams’ properties is obtained using an optically addressable spatial light modulator incorporated into a Sagnac interferometer. Forked computer-generated holograms allow introducing different topological charges while orthogonally polarized beams within the interferometer permit encoding the spatial distribution of polarization. We also demonstrate the generation of complex waveforms obtained by combining two orthogonal beams having both radial modulations and azimuthal dislocations.

Design of optical fiber devices by numerical simulation

We analyze by numerical simulation the optical intensity transmission of several optical waveguide devices. We present characteristic transmission curves for optical fiber sensors and selective WDM channel filters. A Computer Aided Engineering program for helping on the design of optical devices is under development.

Modeling of optical fiber sensors by beam propagation

We used beam propagation methods to numerically simulate straight and short-bend optical fiber sensors. The methods are specifically applied to polymer jacket optical fiber temperature sensors and our results show the main features presented by the experimental data.

Diffracted optical vortices by an angular aperture

The measurement of the topological charge of laser beams with orbital angular momentum (OAM) is key to many applications like deciphering information encoded in several channels. Current techniques useful for that purpose are interferometry, diffraction through different poligonal apertures like triangular or pentagonal and, azimuthal and radial decomposition. A less explored issue is the diffraction of OAM beams through circular sectors. Jack et al. studied the angular diffraction of Gaussian beams (whose OAM is null) through a circular sector. By means of a Fourier transform of the truncated Gaussian beam they showed that the orbital angular momentum spectrum of the transmitted beam has a sinc-shaped envelope centered at zero orbital angular momentum, the width of which increases as the central angle of the circular sector decreases. We analyze here the spectrum of a laser beam with integer OAM that has been diffracted by a circular sector. We present results for circular sectors of different central angles. For circular π-sector, we also study the influence of the transmittance in the OAM spectra of the transmitted beam, using straight borders of nanometric thin films of titanium oxide with different thicknesses. We use a spatial light modulator with a fork hologram placed on to generate the incoming OAM beam and measure the evolution of the intensity profile of the diffracted beam as it propagates away from the circular sector. The spectra of the diffracted OAM beams are shown numerically and experimentally to have a sinc shaped envelope centered at the OAM value of the incoming OAM wave.

Probability losses in controlled cold dipole-dipole collisions

Atoms confined in Wannier vibrational states of an optical lattice with polarization gradient collide elastically via the long-range quantum dipole-dipole interaction. Since the effective Hamiltonian is non-Hermitian, spatially modulated two-atom relaxation rates are present and a high loss on the occupation probability of the vibrational state occurs during the collision.

Simplified Slab Waveguide Three-Level Model for Short Length EDFA Pumped at 1.48 m

We adopt a three-level scheme for the pump - amplification process in 1.48 mm pumped Erbium-Doped Fiber Amplifiers, which reproduces the main experimental features of amplifiers with short and long fiber lengths. Continuous wave amplification in a simplified slab waveguide structure is simulated by means of the scalar Beam Propagation Method, taking into account signal and pump propagation through the waveguide. Results from the simulation are compared with measurements done by the COST 217 Project Group. The method may be well suited for the project of Integrated Optics Optical Amplifiers based on rare earth doped waveguides.

Educational fiber optic transmission equipment with dedicated BER features

We designed a lov cost optical transmission system for use in undergraduate courses in physics and engineering. The system includes boards for bit error rate (BER) measurements, digital and analog transmitters and receivers, master clock, pseudo-random sequence, and noise generators. Programmable logic components were used for both, the BER meter and the pseudorandom sequence generator. The cost, of the equipment and its design simplicity makes it suitable for most teaching laboratories.