E. Alvarado-Méndez

Stimulated Raman scattering in a fiber with bending loss

Stimulated Raman scattering is investigated in a 100-m long single mode fiber with bend-induced loss which has a steep wavelength dependence. The wavelength dependent loss can be used to suppress the second Stokes conversion resulting in an increased first Stokes intensity. Our experiments with a Q-switch Nd:YAG laser produced a rectangular first Stokes pulse at the fiber output.

Total internal reflection of spatial solitons at interface formed by a nonlinear saturable and a linear medium

Abstract We study numerically and experimentally the reflection of spatial solitons at the interface between a nonlinear saturable-type medium and a linear one. We emphasize on determining the physical conditions under which the reflected beam at the interface conserve its nondiffracting properties. Depending on the incidence angle, we find three critical regions for spatial soliton conservation after reflection. We numerically show that the nonlinear Goos–Hanchen shift can have a dramatic effect on the diffracting properties of the reflected beam.

Experimental study on a broad and flat supercontinuum spectrum generated through a system of two PCFs

In this letter, the experimental results on a supercontinuum signal are presented based on a significantly broad and highly flat final spectrum (~810 nm and less than 3 dB). The supercontinuum was induced by two different microstructures in photonic crystal fibers (PCFs) with solid cores, pumped in the nanosecond regime (large pulses) by a Q-switched Nd:YAG laser. The simultaneous presence of both PCFs allowed an optimized spectrum to be obtained in comparison with the work reported in recent papers. The spectral evolution of a pump pulse propagating into the two PCFs was analyzed experimentally and the dispersion in the PCFs was estimated through numerical simulations. The broadening of the final spectrum was related to nonlinear phenomena such as modulation instability, stimulated Raman scattering, four-wave mixing, self-phase modulation, cross-phase modulation and the formation of higher-order solitons. The proposed scheme may have potential applications for the use of supercontinuum spectra in the areas of sensing, spectroscopy and metrology.

Analysis of a Sagnac interferometer with low-birefringence twisted fiber

Abstract The fiber Sagnac interferometer of low birefringence and twist is analyzed numerically in the linear region. A novel method for measurement of the birefringence of the fiber and the angle of rotation of the axes inside the fiber loop of the interferometer is also presented.

Nonlinear optical characterization of ionics liquids

In this work, we show results about the nonlinear optical characterization for four ionic liquids (ILs), namely 1-buthyl-3- methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-ethyl-3-methylimidazolium Bis((trifluoromethyl)sulfonyl)imide ([EMIM][TF2N]), 1-ethyl-3-methylimidazolium trifluoroacetate ([EMIM][CF3COO]),1-buthyl-3-methylimidazolium trifluoroacetate ([BMIM][CF3COO]), using z-scan technique.

Internal reflection of one-dimensional bright spatial solitons

We study the reflection of one-dimensional spatial solitons at the non-linear interface between a Kerr-type medium and a linear medium. Our study places emphasis on determining the physical conditions under which the beam reflected by the non-linear interface is still a spatial soliton. We find that for small angles of incidence an elastic internal reflection takes place, in the sense that the reflected soliton is essentially the same as the incident one. For incidence angles near a critical angle, the reflected soliton becomes less intense and its reflection angle is smaller than the angle of incidence. Finally, for spatial solitons with input angles well above the critical angle, the main part of the energy is transmitted to the linear medium, and no soliton is internally reflected.

Nonlocal nonlinear refraction in Hibiscus Sabdariffa with large phase shifts

In this work we present a study of nonlinear optical properties in organic materials (hibiscus sabdariffa). Our results demonstrate that the medium exhibits a highly nonlocal nonlinear response. We show preliminary numerical results of the transmittance as nonlocal response by considering, simultaneously, the nonlinear absorption and refraction in media. Numerical results are accord to measurement obtained by Z- scan technique where we observe large phase shifts. We also analyze the far field diffraction ring patterns of the sample.

PC-Based systems for experiments in optical characterization of materials

An automatic control for applications of optical characterization of materials using the optical Z-Scan technique is presented in this work. The emphasis is placed in the design of the graphical user interface (GUI) and the automation process. For this purpose, we use a USB data acquisition module with programmable I/O ports for control and signals acquisition for the complete system. The control software was developed using the graphical programming language LabVIEW® and compiled in order to obtain a portable system with the hardware used in this work.

Fabrication of Mach-Zehnder interferometers with conventional fiber optics in detection applications of micro-displacement and liquids

In this paper we shows the results obtained to fabricate and implement Mach-Zehnder interferometers of conventional fiber optic using Long Period Fiber Gratings (LPFG´s) which were developed by electric arc technique. We obtains this type of interferometer when we fabricated two LPFG’s in series or in cascade with the same characteristics such as number of discharges and the same period, placing them in cascade separated by a distance which three times the length of the LPFG. The application which was given at interferometer fabricated was as a liquids sensor, volume sensor of liquids and micro-displacement sensor. The sensors of liquids and liquids volumes were placed in a container in which the interferometer is fixed so that results of measurements are only by incorporating each of the liquid and not by some external movement. The sensed fluids were: water, alcohol and solution (water with sugar). Final length of the interferometer is between 4 to 6 cm. We analyze the results obtained to when a section the Mach-Zehnder interferometer is displaced in of the order of microns. The variations observed in transmission spectra obtained from each of the sensors mentioned, show changes in the amplitude and the attenuation peak of the interferometer was displaced.

Self-diffraction properties in nanotubes (CNTs)

Nonlinear effects are consequence of interaction of height intensities of energy with the matter. Self-diffraction is nonlinear effect and rings are produced. We analyzed the increase of rings due to changes in intensity of CW Ar laser that modify the nonlinear refractive index. The Carbon Nanotubes (CNTs) were dispersed on different solvents: a) water, b) ethanol, c) isoprophanol, and d) acetone. The concentrations were 10ml:1mg in all samples. The dependence between power and concentration of CNTs is shown.