T. Flores

Laser-Induced Breakdown Spectroscopy (LIBS) Quality Control and Origin Identification of Handmade Manufactured Cigars

Tobacco is an agricultural product originating in America that is obtained by processing the leaves of various plants of the genus Nicotiana tabacum. It is the inedible product occupying the most plantings in the world, according to a recent report from the United Nations Food and Agriculture Organization. It is consumed in various ways, but the most popular form of consumption is, undoubtedly, by smoking cigarettes. A particular segment of the tobacco industry is the manufacturing of handmade cigars, which for some third-world countries is an important source of income. There are different qualities of cigars, and a major problem is the adulteration that occurs, for example, when authentic high-quality leaves are replaced by lower quality leaves. A factor that influences the quality of the cigars is the smoke combustion process, which depends on several factors, particularly the composition of the leaves. We present a simple and quick technique for the quality control and origin identification of handmade cigars that measures the Mg/Ca ratios in the tobacco leaves and wrappers of the cigars using laser-induced breakdown spectroscopy.

Self-absorption influence on the optical spectroscopy of zinc oxide laser produced plasma

Optical spectroscopy is used to study the laser ablation process of ZnO targets. It is demonstrated that even if Partial Local Thermal Equilibrium is present, self absorption process leads to a decrease of recorded lines emission intensities and have to be taken into account to obtain correct values of such parameters. It is presented a method that combines results of both Langmuir probe technique and Anisimov model to obtain correct values of plasma parameters.

On the use of shockwave models in laser produced plasma expansion

Interaction of medium to high peak power laser pulses with solid materials produces a plasma that expands supersonically. Expansions of such plasmas have been studied and several models have been proposed to describe it. This work presents a study of the expansion of laser produced plasmas in both vacuum and gas environment by using Langmuir probe and photography. It compares some of the most used models to identify that which better describes the expansion process. In vacuum, such process is properly described by the Anisimov model. However when expanding in a background gas it is found that the Sedov-Taylor model fits properly the position of generated shockwave but overestimates both kinetic energy and pressure of the expanding plasma. Such problem is solved by using a modification of the Freiwald-Axford model. Finally it is demonstrated that after the plasma stopping distance the plasma inters in a diffusive regime

Pulsed Laser Deposition of PbTe in Monopulse and Multipulse Regime

We made a comparison between pulsed laser deposition with excitation in monopulse and multipulse regime. We find stoichiometric ablation when PLD is conducted with multipulse laser but the ablation process is less effective.

Laser induced micro-cracks formation inside the glass, LIBS, and PILA measurements

An experimental measurement by using Laser Induced Breakdown Spectroscopy (LIBS) and Photoacoustic Induced by Laser Ablation (PILA), in order to monitoring the microcraks formation inside the glass induced by laser pulses is presented in this work. The laser was operated in both single pulse and multi-pulse Q:Switched regime using a passive Cr:YAG crystal as switching element. The LIBS spectra captured inside the glass avoid identifying the sample composition without influence of surrounding atmosphere like occurs if the spectra are obtained on the surface. On the other hand, the PILA signal permits to monitor the process and its dependence from the number and intensity of micro-pulses.

Bismuth thin films obtained by pulsed laser deposition

In the present work Bi thin films were obtained by Pulsed Laser Deposition, using Nd:YAG lasers. The films were characterized by optical microscopy. Raman spectroscopy and X-rays diffraction. It was accomplished the real time spectral emission characterization of the plasma generated during the laser evaporation process. Highly oriented thin films were obtained.

Automated system for acquisition and image processing for the control and monitoring boned nopal

This paper describes the design and fabrication of a system for acquisition and image processing to control the removal of thorns nopal vegetable (Opuntia ficus indica) in an automated machine that uses pulses of a laser of Nd: YAG. The areolas, areas where thorns grow on the bark of the Nopal, are located applying segmentation algorithms to the images obtained by a CCD. Once the position of the areolas is known, coordinates are sent to a motors system that controls the laser to interact with all areolas and remove the thorns of the nopal. The electronic system comprises a video decoder, memory for image and software storage, and digital signal processor for system control. The firmware programmed tasks on acquisition, preprocessing, segmentation, recognition and interpretation of the areolas. This system achievement identifying areolas and generating table of coordinates of them, which will be send the motor galvo system that controls the laser for removal

Ray trace algorithm description for the study of pump power absorption in double clad fibers.

An algorithm for the analysis of the double clad fiber design is presented. The algorithm developed in the MATLAB computing language, is based on ray tracing method applied to three-dimensional graphics figures which are composed of a set of plans. The algorithm can evaluate thousands of ray paths in sequence and its corresponding pump absorption in each of the elements of the fiber according to the Lambert-Beer law. The beam path is evaluated in 3 dimensions considering the losses by reflexion and refraction in the faces and within the fiber. Due to its flexibility, the algorithm can be used to study the ray propagation in single mode or multimode fibers, bending effects in fibers, variable geometries of the inner clad and the core, and could also be used to study tappers.

Optical detection of nopal spines for laser de-thorning process

A new optical method for detection of spines during the laser de-thorning process is presented. The spines detection is performed by on-line measurement of reflectance using a low power 532 nm, CW Nd:YAG laser. Its demonstrated that the method avoids enhancing the throughput and efficiency of laser dethorning of opuntia.

On the Nd:YAG pulsed laser processing of rigid PVC

The potential of Nd:YAG pulsed laser to processing PVC sheets minimizing HCl gases emission is investigated. We studied the gas emission when the PVC is cut by either CO2 or Nd:YAG pulsed laser by using FTIR Spectroscopy. Optical microscopy of laser treated PVC samples was performed in order to demonstrate the carbonization. On the other hand, LIBS spectroscopy for two different ranges of pulse duration was employed in order to investigate the plume composition during the Nd:YAG pulsed laser ablation process. The experiments shows that Cl atoms are emitted during the Nd:YAG pulsed laser ablation although the HCl gases are produced at low levels. In order to explain the sub-surface irregularities detected for Nd:YAG laser irradiation, a one-dimensional model is developed to study the temperature evolution inside the sample. We demonstrate that the ablation mechanisms prevail on thermally drive emission until 70 μm, afterwards the thermal expansion process is already observed.