This PDF contains the front matter associated with SPIE Proceedings Volume 6422, including the title page, copyright information, table of contents, symposium committee listing, introduction, and list of symposium sponsors.

Our work presents a study of the physical phenomena produced in biological-tissue irradiated by pulsed lasers. It is of special interest to us to apply short (Nd:YAG, 5ns) and ultrashort (Ti:Sapphire, 90fs) laser pulses into biological-tissue samples in order to study and understand the interaction features. These laser pulses posses interaction features with tissue that could offer, depending on the pulse parameters, good advantages for medical applications; such features include free heat laser pulse-tissue interaction and excellent mechanical damage confinement. This study was carried out in porcine corneal tissue and biological-tissue models made by agar gel layers combined with organic dye, which allowed us to emulate vascular tissue. The main objective of our study is to understand photo-induced thermal effects and bubble formation in biological-tissue irradiated by short and ultrashort laser pulses. Our results on corneal tissue showed a good potential for novel ophthalmic applications, especially in refractive surgery. In the case of the agar gel biological-tissue models, similar results can be applied in dermatology in order to remove port wine stain or other similar birthmarks.

This work presents an experimental study of the appearance of redness on the surface of the eye on PC users due to the exposition to low frequency electromagnetic fields LF, VLF and ELF that VDTs with TRC monitors radiate, based on the measurement of the level of pigmentation and temperature. The total of the samples was analyzed using digital processing of images extracting the component of red color of the sclera. We demonstrated that under the same ergonomics and operating conditions, TRC monitors cause a higher heating and greater pigmentation in the users eyes as compared to LCD screens, due to the higher low frequency radiation.

Recently, within the cytogenetic analysis, the evolutionary relations implied in the content of nuclear DNA in plants and animals have received a great attention. The first detailed measurements of the nuclear DNA content were made in the early 40's, several years before Watson and Crick proposed the molecular structure of the DNA. In the following years Hewson Swift developed the concept of "C-value" in reference to the haploid phase of DNA in plants. Later Mirsky and Ris carried out the first systematic study of genomic size in animals, including representatives of the five super classes of vertebrates as well as of some invertebrates. From these preliminary results it became evident that the DNA content varies enormously between the species and that this variation does not bear relation to the intuitive notion from the complexity of the organism. Later, this observation was reaffirmed in the following years as the studies increased on genomic size, thus denominating to this characteristic of the organisms like the "Paradox of the C-value". Few years later along with the no-codification discovery of DNA the paradox was solved, nevertheless, numerous questions remain until nowadays unfinished, taking to denominate this type of studies like the "C-value enigma". In this study, we reported a new method for genome size estimation by quantification of fluorescence fading. We measured the fluorescence intensity each 1600 milliseconds in DAPI-stained nuclei. The estimation of the area under the graph (integral fading) during fading period was related with the genome size.

The coherent light communication systems have several advantages compared to the intensity-modulation direct-detection systems (IM-DD). The most important advantages are that offer increases transmission capacity and in principle they will limit only by the shot noise. However, there are important conditions for these systems, are that the beams must be mutually coherent, with the same polarization and, mechanisms to compensate the slow shift phase. Therefore the construction of these systems is generally most expensive that IM-DD systems. Nevertheless the use of adaptive photodetectors allows an easy implementation of this type of systems. In this work the results of a system that evaluates distances by means of an ultrasonic sensor and a coherent light communication system to send the information, with an adaptive detector based on the photo-EMF effect, are shown.

In this work, we propose a set of photonics devices that can be employed as part of optical communications systems. These devices consist of an isolator, a circulator, a multiplexer and a pump concentrator, and are based on the functionality of an optical paraboloidal mirror. The devices were first studied using software for optical modeling and then were experimentally tested. For the cases of the isolator and the circulator, we obtained numerically roughly 50 dB of isolation. Furthermore, we proposed a simple and a novel multi channel multiplexing device, and finally, we asses the alternative and elegant way of the combination of high power multimode diode laser to increase the power capability of diode laser systems that are commonly used in high power fiber laser. In all the cases, the design showed the advantage of the easiness of alignment and the simplicity to implement.

We present results on the usefulness of multilevel networks from the viewpoint of Radio over Fiber networks. We show results of several topology options as star, ring, multi-level ring, multi-level star, hybrid multi-level ring/star and hybrid multi-level star/ring. We present comparative results of the topologies in terms of fiber distance, and reliability of the networks.

We present a low-cost kit to support optical communications courses teaching. The kit contains a students manual that can be used to explore the basic phenomena involving optical transmission and reception phenomena, a transmitter module, and a receiver module.

It is presented an educational kit to show physical principles: momentum, free fall and measure of gravitational constant for an object in movement. These principles are reproduced using mechanical parts, optical sensors and laser to send a signal into a computer. Data results are acquired and analyzed to demonstrate that the results are concordant with the theory. The results are into a 10% of error far of the known values for gravitational constant on Earth. This educational and demonstrative kit can be use in elementary and undergraduate level; it has as proposes to be a base to show complex experiments and advanced theory.

In this work it is presented the case peculiar of the design and the construction of a table of coordinates using optic sensors as way of control. This prototype arises like an educational strategy, through which is sought that the students of the first years of the careers of Engineering in the Polytechnic University of San Luis Potosi feels incorporate to a concrete project in which they integrate the acquired knowledge to the beginning of its professional formation.

This paper presents results obtained in the "Science at your school" project made at Universidad Autonoma de Baja California. In this Project, science spreading activities were developed by undergraduate engineering students and were oriented to previous educational levels. This activities included basic science or engineering science concepts and applicated engineering prototypes. The work shows the operational structure in which the program was conceived and approved. Ten prototype activites were developed to spread scientific knowledge. These prototypes included electronic instrumentation application to characterize a sphere's trayectory on a inclined plane using optical sensors. This first stage of the project settles the basis to continue (a) promoting to previous educational levels the interest by the science and engineering, (b) motivating primary level and secondary level students adequate information about some specific engineering fields that they want to study in a future and (c) to link physical and human resource highly specialized in the UABC with previous educational level, and in consequence, to achieve the university to play a bigger role in teaching basic sciences.

Science and technology disclosure is an integral part of our scientific work as researches; it is an induction process for children, young people and teachers of primary and secondary schools in the state of Queretaro. Education must be offered in a clear and objective way, it allows to the students apply the acquired knowledge to understand the world and improve his quality of life. Nowadays, the Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada of the Instituto Politecnico Nacional Unidad Queretaro (CICATA-IPN Queretaro) together with the Consejo de Ciencia y Tecnologia del Estado de Queretaro (CONCYTEQ) have implemented the "Science and Technology for Children" program (Ciencia y Tecnologia para Ninos - CTN), it allows to the educative sector obtain information through the CONCYTEQ web page. The fist stage of the program was the development of two subjects: the brochure titled "Petroleum, Nonrenewable Natural Resource that Moves the World" and the manual "Experiments of Physics". At the moment we are working with the second stage of the program, it is about the energy generation using renewable sources such as: geothermal, aeolian, solar and biomass. The CTN program allows to students and teachers to create conscience about the importance of the development of the science of technology in our country.

In this work an optical instrument for measuring tilt is described. The device is compact, requires no special handling and can measure variations in tilt of the order of 0.5 arcsec, although this value can be suitably modified by changing the setup parameters. The instrument was developed as a tiltmeter using a liquid surface as reference surface. The inclination is obtained by measuring the longitudinal displacement of a laser beam after being reflected from the surface of the liquid. The application of the instrument for measuring the tilt of the spindle of a polishing machine of large dimensions is presented.

The necessity of detection and recognition of different types of gases, such as volatile organic compounds, which are frequently found in food and beverage industries among others, requires the development of different types of sensors. In this work, an application of optical fiber for the detection of volatile organic compounds, particularly ethanol is presented. The sensor was constructed removing a portion of the cladding and depositing instead a sensing titanium dioxide (TiO₂) film doped with an organic dye (rhodamine 6G) by the sol-gel method. The sensor response was measured in a Teflon chamber where the sample to be measured was injected. A He-Ne laser beam was coupled to the fiber and the variation in the output power was measured which indicates the gas presence. The difference between the output power with and without gas gives a measure of the concentration that exists in the chamber. The experimental results showed that for an ethanol concentration range from 0 to 10500 ppm, the response of the sensor was approximately linear with a correlation coefficient of 0.9924.

Solutions of bovine serum albumin protein were heated from 30 to 85°C in a temperature-controlled optical cell equipped with air-convective and ohmic heating systems. A polarized laser beam passed through a photo-elastic modulator was used to measure system changes in optical rotation. Results using both the air-convective and the ohmic heating systems showed that when the protein system was heated, an increase in absolute value of optical rotation occurred close to the temperature of denaturation of the protein. Both heating systems were compared, evaluating data points spread and variation in calculated temperature of denaturation for the replicates. Although no improvement in these parameters was obtained with ohmic heating when compared to those obtained with the air-convective system, the optical change related to protein denaturation was more clearly observed. Because ohmic heating strongly interacts with the sample under study, samples with low polarity and not susceptible to electrolysis should be used to avoid electrical effects; regardless, ohmic heating coupled to optical systems could also be a useful tool for the evaluation of interaction of electric field with biological systems optically active.

In this study, the objective was to evaluate optical properties of a corn starch-water mixture as descriptors of its behavior under processing conditions. A solution of corn starch in water was prepared and heated from 25 to 85°C in a temperature-controlled optical cell. For the measurement of optical properties, a polarized laser beam modulated through a photoelastic modulator and an analyzer, was used as optical probe. It was possible to measure transmitted light, along with optical rotation. Optical measurements showed changes related to temperature dependent phenomena such as starch granule swelling and gelatinization, in the ranges 25 to 60°C, 60 to 85°C. Above 80°C transmission values were higher, due to the solution clarification caused by corn starch gelatinization. Regarding optical rotation, it was difficult to obtain reliable measurements at low temperatures due to the high turbidity of the system. However, once gel was formed at higher temperatures, optical rotation and light transmission increased. This study demonstrated that optical techniques are suitable for the study of the behavior of water-starch mixtures under processing conditions such as heating, revealing a promising future for the monitoring of such phenomena in the production line to lower costs and improve product quality.

Two techniques for monitoring temperature and pressure variations over surfaces using sensitive paints are presented. The analysis is done by the acquisition of a set of images of the surface under analysis. The surface is painted by a paint called Pressure Sensitive Paint (PSP) for pressure measurements and Temperature Sensitive Paints (TSP) for temperature measurements. These kinds of paints are deposited over the surface under analysis. The recent experimental advances in calibration process are presented in this paper.

Due to the increase in the incidence of cracks in a specific model of side-view mirrors provided with an anti-fog thermal resistance, the heating process of the mirror was analyzed using an infrared camera and the results were compared to a different model that had a very low incidence of cracks. The heating velocity and temperature distribution over both sets of mirrors was tested by recording the video output from an infrared camera while the mirrors were heated up with its internal heating resistance. The thermal videos showed that the model that cracked frequently had a higher temperature, an uneven temperature distribution and reached its highest temperature faster than the model that did not crack easily. These findings show that the design of the thermal resistance used to heat mirrors as an anti-fog technique has an influence on the quality and durability of rear view mirrors.

Bearings are elements of rotating machinery that are widely used as low friction joint elements between other machine elements. Like any other machine element they posses a finite life which is dependent on a number of factors, among them manufacture, assembling, maintenances, load, etc. Bearing failures are amongst the principal causes of machinery overhaul. They by themselves are a source of vibration which is a function of surface conditions, clearances, misalignment, etc. Each of these defects present a specific dynamic signature, and can be analyzed by a number of techniques already in used, among them the laser vibrometry. This is a non-contact, non-disturbing method commonly used for measurements of vibrations on static objects. The technique offers the possibility to measure vibrations on thin-walled (light), and rotating objects as well as sound fields. Common vibration signal analysis in rotating machinery are restricted to low frequencies, up to 3000 Hz, and in some cases when analyzing contact problems and fatigue at 7000 up to 15000 Hz. In this work, are presented the primary results to employ laser interferometry to study the dynamic signals generated by rolling bearings, and the feasibility to employ it to study high frequency problems of these machine elements.

The reconstruction of the object surface with inherently discontinuous regions is usually a difficult problem by using standard phase unwrapping technique i.e. the spatial unwrapping. To recover the range data of such a surface, Huntley and Saldner recently proposed a temporal phase unwrapping procedure (TPUP) and Peng X. et al. based on their work proposed an enhanced recursive scheme for the TPUP. However the phase jumps no necessarily they correspond to multiples of 2pi exactly. Due to this, an enhanced scheme for temporal unwrapping in order to increase its efficiency is introduced. Additionally, we present some results obtained by mean of temporal unwrapping and spatial unwrapping, in order to compare them and to demonstrate the effectiveness of the temporal unwrapping.

In this work, a study for the measurement of a nonspecular object shape by using the fringe pattern projection technique is presented. This study uses only one modulating grating, unlike the moire projection method, which uses two modulating gratings. The proposed method was tested with several objects, and the results will be shown at the end of the presented work. To obtain the modulating phase of the generated fringe patterns, we used step phase shifting algorithms and the Fourier transform method. The obtained results show that the proposed method has an acceptable precision with errors around 0.5%.

Speckle interferometry is a powerful and basic technique to test mechanical parameter. Traditional speckle interferometry is implemented in laboratory, with bulk components. On the other hand, real applications demands of more practical set-ups: compact and robust. Optical fibers present a possibility to substitute some bulk components and to access far and adverse mediums. Based on our experimental experience we discuss the advantages and disadvantages in the implementation of optical fiber in speckle interferometry. In order to observe high constrast of fringes; we tested different and conventional fiber. We compare results from different types of fibers and discussed the viability to implement it in optical speckle interferometry.

Light-emitting diodes (LEDs) can be chosen to emit light in a wide variety of highly saturated colors. As a consequence, a hybrid lamp assembled with colored LEDs and with one incandescent or fluorescent source easily allows the user to dynamically select the desired color point without additional filters, with high color rendering index, and at a low cost. We measure some properties of a color tunable lamp that uses both colored LEDs and an incandescent or a fluorescent source. For the LED-incandescent type, we assemble an array of blue LEDs with a typical incandescent bulb source, and to assemble a LED-fluorescent type we used an array of red LEDs with a commercially available compact fluorescent lamp. Incandescent and fluorescent sources have a fixed intensity, while LED intensities are adjusted to tune color. For LED-incandescent lamps, our experimental data show that the correlated color temperature (CCT) can be linearly tuned with the electric current of the LED array. The LED-fluorescent lamp exhibits a CCT that exponentially varies with the drive current of red LEDs.

Recently, Light Emitting Diodes (LEDs) have found several applications from lighting to automotive displays, screens, traffic signaling and many other. These emerging applications require some of their visual quality characteristics to be measured as accurately as possible in an objective physical manner. Therefore the Photometry Laboratory and the Sources Spectroradiometry Laboratory of the Centro Nacional de Metrologia (CENAM) of Mexico have started with the development of photometry and radiometry measurement capabilities for LEDs in order to provide the industry with the necessary metrological infrastructure. In this paper we present the first results obtained at CENAM for the measurement of the luminous flux and the determination of the correlated color temperature of a couple of commercial white LEDs sources used for lighting. The values obtained for those quantities are presented here together with their corresponding estimated uncertainties and provided with traceability to the SI units through the national standards maintained at CENAM.

We propose the construction of electromagnetic and electronic multicavity resonators based on the mechanism of dynamical tunneling proper of mixed chaotic systems. We use chaotic two-dimensional (2D) waveguides formed by a linear array of coupled cavities whose geometrical parameters are chosen to produce mixed phase space: chaotic regions surrounding islands of stability where ray (particle) motion is regular. Rays (particles) coming into the waveguide cannot penetrate into these islands but incoming plane waves tunnel into them at a certain discrete set of frequencies (energies) forming quasi-bound states. In this paper we demonstrate the tunneling mechanism in 2D waveguides and how it can be used to design multicavity resonators. We also discuss possible applications in the construction of microlasers and electro-optical beam splitters and switches.

The wavelength division multiplexor (WDM) has a great importance in the technology of the communications by optical fiber, is an economic and efficient form, to increase the capacity of transmission by several orders of magnitude, reason why it is desirable to have laser sources of multiple wavelengths in a system WDM, which, according to reported works, have been obtained using diverse types of filters. In this work we presented a laser of multifrequency emission, of Erbium doped optical fiber, tuned with an optical fiber filter. The configuration of the optical filter, presents high stability and low lost by insertion, independence to the changes of polarization, low powers of light entrance, and has an useful spectral wide. It has the advantage to have a simple design and easy manufacture in addition to his low losses.

Ytterbium absorbs at 915 and 976nm. It also emits at 976nm and from 1060nm to even 1150nm, showing a quantum efficiency of up to 86%. In this experimental work, our novel inner cavity structures were firstly characterized and studied as free-running lasers from the 4% Fresnel reflection from the flat-cleaved fiber facets. The available pump source, a commercially available laser diode, had a maximum power of 0.5W at 915nm from which a coupled power (into the inner cladding) of 1W was reached; fiber laser efficiency reached, in our best case, 55% with respect to launched pump power. For the second part of the work, polarization controlled Yb-doped fiber laser cavities were studied by way of inserting a polarized beam splitter and a &lgr;/4 wave-plate into de cavity. From this, 177mW of single polarization output were obtained by rotating the wave-plate until the maximum points were identified on a wave-plate angle vs. output power plot. The maximum output power was 200mW from 60° to 90° aprox. Now, based on the data obtained, one can claim that at least 40% of the maximum output power available from the laser was linearly polarized. Finally, a 600 lines/mm bulk grating was employed in order to obtain laser tuning results on a traditional way. i.e. by reflecting lasing into the cavity and selecting output from the close end. The tuning range was measured to be from 1088nm up to 1097nm. All these results and possible applications will be discussed in detail.

We report the observation of Mathieu-Gauss modes generated in a stable CO₂ laser resonator composed by an axicon and a plane mirror. Several low order even and odd Mathieu-Gauss modes were obtained by slightly breaking the symmetry of the cavity. Intracavity elements were used for obtaining odd Mathieu modes. The nondiffracting nature of the Mathieu-Gauss modes is measured indirectly by recording their annular spectra at the focal plane of a converging external lens. The experimental results are corroborated with theoretical predictions.

A very simple and cost-effective technique for wavelength tuning a fiber laser using multimode interference effects is demonstrated. The tuning mechanism relies on the self-imaging effect which occurs in multimode waveguides. The tuning mechanism consists of a section of multimode fiber (MMF) spliced to a single mode fiber (SMF), with a broadband mirror located at the other end of the MMF. The signal coming out of the SMF will be imaged within the MMF at a very specific location. Therefore, if the length of the MMF is slightly shorter than this length, the image will be formed in free space. By placing the mirror at this position, the light is reflected back through the MMF and SMF. Since the self-imaging is wavelength dependent, the position of the re-imaging point will depend on the wavelength, and the laser wavelength can then be tuned by varying the distance between the MMF facet and the broadband mirror. To obtain a stable system and easy to align mechanism an integrated fiber gripper was fabricated on silicon wafer. This novel tuning device was incorporated into a double-clad Ytterbium-doped fiber laser (DCYDF), and the tuning characteristics were evaluated by varying the distance between the broadband mirror and the output facet of the MMF. The mirror was moved in 25 microns steps, and the optical power and spectrum measured at every step. A tunability of 12.24 nm was measured with this implementation, and the laser system was shown to be very robust and highly stable. We believe that further improvement in our system will lead to a wider tuning range.

Laser shock processing (LSP) or laser shock peening has been proposed as a competitive alternative technology to classical treatments for improving fatigue and wear resistance of metals. This process induces a compressive residual stress field which increases fatigue crack initiation life and reduce fatigue crack growth rate. We present a configuration and results in the LSP concept for metal surface treatments in underwater laser irradiation at 1064 nm with and without a thin surface paint layer. A convergent lens is used to deliver 1, 2 J/cm² with a 8 ns laser FWHM pulse produced by a 10 Hz, Q-switched Nd:YAG laser with a spot diameter of a 1,5 mm moving forward along the workpiece. A LSP configuration with experimental results using a pulse density of 5000 pulses/cm² in 6061-T6 aluminum samples are presented.

An automatic technique for shape modelling is presented. The approach of this technique is the object representation by means of a mathematical model. To carry it out, a neural network is implemented to perform the object modelling. The model provided by the neural network is performed based on the surface data. To detect the surface data, the object is scanned by a light line. Thus, the laser metrology provides the surface data to construct the model by means of the network. This process involves image processing of a laser line pattern. The approach of the neural networks is to perform the object modelling without measurements on the optical setup. Thus, the setup performance and accuracy are improved. It is because the errors of the measurement are not added to the computational model. To describe the accuracy a root mean square of error is calculated using data provided by the network and data given by a contact method. This technique is tested with real objects and its experimental results are presented.

A simple and automatic wavefront reconstruction is presented. This technique is based on the use of a plane computer display (a thin film transistor monitor) to generate the fringe patterns and compute the gradients field produced by the phase object. The accurate reconstruction is proved by the estimation of the surface map of a progressive ophthalmic lens, which is obtained using computational efficient techniques for the fringe pattern demodulation and gradient field integration.

Risley prisms are commonly used in continuous scanning manner. Each prism is capable of rotating separately about a common axis at different speeds. Scanning patterns are determined by the ratios of the wedge angles, the speed and direction of rotation of both prisms. The use of this system is conceptually simple. However, mechanical action in most applications becomes a challenge often solved by the design of complex control algorithms. We propose an electronic servomotor system that controls incremental and continuous rotations of the prisms wedges by means of an auto-tuning PID control using a Adaline Neural Network Algorithm, NNA.

In this work an implementation of angular sensor movements is made based on the Sagnac effect, made it in volume optics, using a detection method of the interference lines and its amplified pattern. The new devices of sensing through optical systems, have given a new vision of measurement and instrumentation, guiding to new studies on designs and prototypes of themselves. An example of these developments is the advance in devices of sensing in fiber optic, such is the fiber optic gyroscope (FOG) which is based on the Sagnac effect. This device has a great sensitivity because the area enclosed by the interferometric ring, is through a fiber optic coil, which increases the sensitivity and diminishes the size of the device. It is possible to indicate that in previous years, with the technology then existing, the utility to use the Sagnac effect like a gyroscope was very limited, because it was just employed to measure angular movements of great magnitudes and with very big areas, since there was not the optical detection systems of the great sensitivity that now exist or coherent sources with high power, indispensable elements in the implementation of the system. For that reasons, the application of this effect began to grow with the development of the fiber optic, and was possible diminish the size and increase the area of the device. Thus the Sagnac effect in volume optics was relegated by the fiber optic interferometer. Nevertheless using the new electronic systems of amplification and optoelectronic devices that now exist, we have rescued the Sagnac effect in volume optics to make measurements of angular velocities in an interferometric system of 0.25m2. For this work, was necessary to create a detection system of great quality, this was made using a detection method of the interference lines and amplification of the interferometric pattern.

Some pH sensors based on optical fibers use organic dyes which are sensitive to the pH levels. Such dyes are deposited over the fiber and they are supported by a matrix, (TiO₂) in this case. In this work, we present the results obtained of the fabrication and characterization of an optical fibers sensor with a thin film doped with two different organics dyes (Rhodamine 6G and Coumarin), deposited in a little section of the optical fiber by the SOL - GEL process. It was found that each dye is sensitive to different pH ranges (2 to 12). The fiber optics sensor can be used for the measured of the pH level of aqueous testing solution, and the combination of the dyes is possible to cover a dynamic ranges from 2 to 12. It is also analyzed the sensitivity of the sensor with the Rhodamine 6G and Coumarin dye for different molar concentrations in a range 0.01% to 0.08% and to determine this way the best concentration for the sensor.

In this work we present our studies of the optical properties of electrically switched Fresnel Zonal Plate using polymerdispersed liquid crystal (PDLC) materials. Our design is interpreted by using a theoretical approach to light scattering in PDLC films that relates optical transmittance and the order parameters, characterizing both the orientational structures inside bipolar droplets and orientational distribution of the droplets. The theory relies on the Rayleigh-Gans approximation and uses the Percus-Yevick approximation to take into account the effects due to droplet positional correlations.

We describe a novel polarimetric configuration which can be used to develop a Saccharimeter. This polarimeter layout consists of an analyzer mounted on rotator 360 stage. The rotating carriage of the stage provides continuous rotation, and generates a reference wave which may be used to generate clock pulses for a digitizing instrument that measures the intensity of the beam emerging from the polarimeter. The detected optical signal is a phase modulated signal, which phase is demodulated by the use of coherent detection method. Finally, experimental results demonstrating the reliability of the instrument are presented.

In this work we present the theoretical basis of two methods applied to the birefringence characterization of single--mode optical fibers and devices. Both methods are based on classical polarization optics and make use of the geometric properties of the Poincare sphere. One of them, used to identify the dominant polarization characteristics, is based on the wavelength scanning technique; i.e. assumes that wavelength dependence can be neglected. The second one, with a higher accuracy, avoids the uncertainty introduced by birefringence dispersion using a monochromatic linear signal to determine the polarization eigenmodes for that specific wavelength. The results obtained for some common cases are presented and discussed.

It has been observed in the literature, developments about characterization of several materials for gas sensing application; simultaneously, also it has been observed that only some of them show a procedure of design for the implementation of these materials in a device or an optical system. In consequence, appears differences between the predicted by theory and the experiments. For that reason, the present work proposes a new approach for the design of optical-integrated (OI) sensors. We show the advances in the design of an OI sensor for ammonia detection (NH₃), using tungsten trioxide (WO₃) as sensitive material. We considered a model that incorporates the concepts of the kinetic of gas adsorption on solids, the effects of the real and imaginary part of the refractive index in the redistribution of the optical field, and the influence of the photo and thermochromism, before and during the sensing mechanism. Although the work has not been concluded, we can affirm that the concepts incorporated in this proposal, must be considered as critical parameters in the design of an OI sensor or an optical fiber (FO) sensor.

This article describes the design and implementation of a photon counting system, which is made using low cost electronic devices. The system is connected to a spectrometer in order to study events related to low levels of luminance intensity. It uses a photo-multiplier tube (PMT) for photon detection. The counting photon system is conformed by 5 stages, which are: the detector, a pre-amplifier, a pulse comparator, a pulses counter and a communications interface in a PC. Data acquisition is done through the serial port. The system allows the detection of radiation coming from signals whose counting rates are several thousands pulses per second. As an application of the system, the Raman Stokes spectrum of the polystyrene as well as the fluorescence band of an organic pigment on a poly-vinyl matrix is showed.

A spatial light modulator (SLM) is a very useful optical tool due its versatility to be manipulated dynamically. We propose a characterization method for reflective SLMs in quasi-normal configuration. This device can work as either amplitude-mostly or phase-mostly modulator. To achieve the modulation, the SLM can be accompanied by two polarizes, or additionally using a quarter-wave plate retarder. By simulating the behaviour of the optical setup for this device; we establish an experimental Jones matrix that represent the modulator. In this work we present a more realistic modulator characterization, only assuming that the modulator Jones matrix should be unitary (the modulator do not absorb light). We report this model for characterization of the Holoeye LCR2500 SLM.

In this paper we propose a high voltage source which is controlled by a communication port I/O of a data acquisition card. The graphical programming language LabView is employed for this task. We make use of this source to produce optical fiber gratings by inducing an electric arc with the point by point procedure. It has a control section to modify the arc duration time and thus the voltage and current applied to the fiber by means of two electrodes. The experimental setup by which we characterized the gratings is depicted and we also present the transmitting spectrum. The gratings were fabricated with SMF-28 fiber but microstructured fiber can be exploited too. These gratings can be used with optical fiber lasers as optical filters and in the implementation of optical sensors.

A birefringence compensation method for a mechanically induced tunable long period holey fiber grating is proposed. With this method the tunable long period holey fiber grating becomes polarization-insensitive. A device with such characteristics is desirable in applications where filter tunability is used to reject (or simply attenuate) non desired optical bands. Characterizations with polarized and nonpolarized light are presented and the potential applications are discussed as well.

In this work we present a security system that uses an optical key as control access device. The optical key is a computer generated hologram (CGH) recorded using optical damage onto a transparent material using a high power pulsed laser. When we reproduce the CGH with a laser we obtain the codified image on the holographic plane. Placing a camera in this plane the reconstructed image is captured. Using a comparing program that contains the prerecorded security image the access is authorized or denied.

We present a numerical and experimental evaluation of two different holographic codes for synthesis of fully complex transmittances. Particularly, Bessel and Laguerre-Gauss beams can be encoded with these techniques. The numerical performance of these computer-generated holograms (CGHs) is evaluated by means of the computation of the Signal to Noise Ratio (SNR) and their experimental performance is evaluated by means of their implementation using a phase-only spatial light modulator (SLM). The results obtained can be useful in many tasks where a high efficiency is required and represent the first comparison between these methods of encoding.

In this work we present the numerical analysis of fully complex fields employing computer generated holograms, implemented with a commercial amplitude liquid-crystal spatial light modulator (SLM). The hologram transmittance is obtained by adding an appropriate bias function to the real cosine computer hologram of the encoded signal. For the purpose of this work, we consider an appropriated bias function for a modulator in which the amplitude transmittance is coupled with a phase modulation. This type of coupled phase appears in a commercial Twisted Nematic Liquid Crystal Display (TNLCD), configured to provide amplitude modulation, with only two polarizers as external components. This modulation curve was experimentally obtained and adjusted to a mathematical function. The numerical evaluation is done by calculating the signal to noise ratio of the reconstructed complex fields for the real modulation curve. Results show that for a good behavior for complex fields a constant bias function should be implemented. As a particular interesting case we generate propagation invariant complex beams with high accuracy and simplicity.

We report a new method based on the ratio of the optical transmittance to monitoring processes of corrosion in stainless steel 304L immersed in a aqueous solution of lithium bromide at 50% wt, at 70°C. The change of the optical transmittance that is measured in the solution contaminated, is related to the physical degradation of the samples of stainless steel. We determine that the optic spectral-interval with more sensitivity to the corrosion products-accumulation, dissolved in the lithium bromide solution is of [450 nm - 750 nm]. A laser at 632 nm is utilized to detect the corrosion oxides-accumulation dissolved in the lithium bromide solution for 20 days. The slope of the change ratio of the optical power of transmittance is of 31X10^-3/hour for 480 hours of exposition. Finally, the experimental results that we have presented, show that this optical technique represents an alternative in the detection of the corrosion without establishing physical contact with the sample.

Reflectance Difference Spectroscopy (RDS) is a powerful tool for the optical characterization of cubic semiconductors. Several physical mechanisms have been identified to contribute to the RDS signal. Among these we can count on surface electric fields, lineal defects, and surface strains. The RDS setups reported so far, use photodiodes and photomultipliers as light detectors and lock-in techniques to process the signal. In the present work we describe a new instrument based on a charged-coupled device (CCD) as light detector. By focusing the light on the CCD, it is possible to obtain the RD spectra coming from different regions of the semiconductor surface, by analyzing the spectra for a group of pixels of the CCD. The instrument can be used to obtain a topographic map of the surface of the semiconductor.

The degradation of weather exposed linear low density polyethylene (LLDPE) specimens, with and without pigments, in Aguascalientes City, Ags. Mexico, during 269 days, was studied. Spectroscopic methods, ultraviolet (UV) spectroscopy and colorimetry, were used to determine the degradation of the specimens. The material used is not pure since they are samples of finished product that contain additives such as anti-oxidants, stabilizers, catalysts. One of the samples contains orange color pigment and the other sample is colorless. The plots describing the absorption bands attributable to the polymeric material show a similar profile in both samples. The bands attributable to pigment do show a considerable decrease in absorbance. The results suggest that the orange pigment has been degrading, as it can also be observed in the color change, while the polymeric material doesn't show any degradation.

This work carries out a simulation of the absorption spectra on the IR of an untinted textile fiber manufactured with polyacrylonitrile (PAN), obtained by calculating the Molecular Orbitals (MOs) and their associated energies based on the semiempirical (AM1) Hartree-Fock (HF) model and compared with the experimental results obtained from a PAN textile fiber with blue pigment by means of an IR FTIR Avatar Nicolete spectrophotometer.

In this paper, we propose a method to determine refractive index changes and its dispersion of diluted solutions by analyzing the refraction of light by a hollow prism containing the medium to be characterized. The system uses a double prism refractometer to compensate the dispersion of the medium and the output beam is analyzed with a spectrophotometer resulting in a faster measurement with a simple setup. The system was calibrated using solutions of sucrose in water. We present experimental results of the characterization and monitoring of water oxidation as an example of potential applications.

In the present work, the temperature versus thermal deformation (strain) with respect to time, of different coating films were studied by a nondestructive technique (NDT) known as shearography. An organic coating, i.e., ACE Premium Enamel, on a metallic alloy, i.e., a carbon steel, was investigated at a temperature range simulating the severe weather temperatures in Kuwait especially between the daylight and the night time temperatures, 20-60 °C. The investigation focused on determining the in-plane displacement of the coating, which amounts to the thermal deformation (strain) with respect to the applied temperature range. Furthermore, the investigation focused on determining the thermal expansion coefficients of coatings, the slope of the plot of the thermal deformation (strain) versus the applied temperature range. In other words, one could determine, from the decreasing value of the thermal expansion coefficients of coatings, a critical (steady state) value of the thermal expansion coefficients of coatings, in which the integrity of the coatings can be assessed with respect to time. In fact, determination of critical (steady state) value of the thermal expansion coefficients of coatings could be accomplished independent of parameters, i.e., UV exposure, Humidity, exposure to chemical species, and so on, normally are considered in conventional methods of the assessment of the integrity of coatings. In other words, with the technique of shearography, one would need only to determine the critical (steady state) value of the thermal expansion coefficients of coatings, regardless of the history of the coating, in order to assess the integrity of coatings. Furthermore, results of shearography indicate that the technique is very useful NDT method not only for determining the critical value of the thermal expansion coefficients of different coatings, but also the technique can be used as a 2D microscope for monitoring the deformation of the coatings in real-time at a submicroscopic scale.

We report on in situ Reflectance Difference Spectroscopy measurements carried out on GaAs (001). Measurements were performed at temperatures of 580 °C and 430 °C, in both n and p-type doped films and for both (2x4) and c(4x4) reconstructions. Samples employed were grown by Molecular Beam Epitaxy with doping levels in the range from 10¹⁶ - 10¹⁹ cm^-3. We demonstrate the potential of Reflectance Difference Spectroscopy for impurity level determinations under growth conditions.

In this work we study the Butterfly Effect and its influence on the efficiency of the Control Methods. A comparative analysis shows that when we applied Control into a bistable system, monostability can be reach for a calculation performed with precision of 6 decimal numbers, although for the same system parameters, this does not happen when the calculation is performed using a precision with 9 decimal numbers.

We focus into the development of an efficient method to control multistable systems in the presence of noise. The method is based on the addition of an external control force in the form of a slow harmonic modulation with properly chosen frequency and amplitude. Although noise is usually a non desirable condition, it has been recently demostrated that in coupled systems cooperative effects of the periodic force and noise are produced. This enhancement phenomena in the response of the deterministic equations is interpreted as stochastic resonance. Our main purpose is to study deterministic resonances between the different solutions of the multistable system and the external modulation. Then, all efforts will concentrate in the enhancement of the control method produced by noise.

We study the three dimensional distributioin of vector Mathieu-Gauss (vMG) beams near the focus of a non-aperturing thin lens. These beams constitute a family of solutions to the vectorial wave equation in the paraxial approximation. We adopt an energy criterion for defining the width of the beam as well as the focal plane. It is observed in our analysis that the focal plane does not coincide with the geometric focus, but it is slightly shifted towards the lens. The dependence of the focal shift on the different parameters of the vMG beams is discussed for beams with different polarizations.

We obtain X-shaped localized pulses based on a superposition of non-diffracting optical fields of different frequencies. We explore the construction of arbitrary traveling electromagnetic pulses that remain invariant in shape and re-derive an expression for these pulses in terms of non-diffracting beams with arbitrary transverse distribution. We emphasize in the known orthogonal families of solutions to the wave equation that have translation symmetries in only one dimension (i.e. Bessel, Mathieu and Parabolic beams). We present several examples of higher order Mathieu localized pulses as well as Parabolic pulses of arbitrary parabolicity. We consider feasible spectral functions in the optical domain.

A novel method of phase differences extraction is applied in order to study vibrations on a homogenous cantilever. It is achieved considering fringe patterns with carrier frequency and slow varying respect to the time. The technique is based on the Fourier-transform method and by the quotient of the two adjacent frames of the patterns. Fringe pattern is obtained by fringe projection on a fixed end homogenous cantilever, undergoing harmonic vibration. With this technique, we can obtain profiles of different vibrating modes of the cantilever for frequencies less than that of the camera frame rate (33.3 ms). In this communication theoretical analysis and experimental profile modes are shown.

This work shows that in many practical situations it is possible to obtain the dielectric constant of coatings on plain conductive substrates by means of a single electrode-sample capacitance measurement without precise knowledge of its thickness. 3D simulations of spherical electrode-dielectric coating-conductive plain substrate capacitive system are performed in order to determine theoretically the suitable electrode dimension for a coating thickness range of interest.

In this paper we present the preliminary experimental results about the measuring of Kerr optical nonlinearity in a 5CB liquid crystal sample doped with methyl-yellow at 1%. These results are obtenided througth Z-scan tecnhique using a simple low power He-Ne laser in CW operation. We observe a great negative Kerr nonlinearity in the sample obtained in the regime temperature of nematic phase. For upper temperature, we observe a notable decreasing of the optical nonlinearity due to sample change to isotropic phase. In adition, we observe the presence of a nonlinear absorption contribution.

A typical rear projection screen is formed by two components: Fresnel lens and lenticular/diffuser plate. This work provides a technique to determinate color uniformity across the screen. Initial results of color uniformity of Fresnel lens and lenticular/diffuser plate indicates a very good uniformity.

In this work, the photon electro-absorption modulation of laser sources used in broadband systems is presented. We begin explaining the optical pulse broadening phenomenon of light pulses that propagate through an optical fiber, which represents a limiting factor for bandwidth expansion on currently installed optical fiber networks. The photon electro-absorption external modulation for light sources is explained further, along with the physical mechanism inherent to this modulation that minimizes the optical pulse broadening. We conclude mentioning the main advantages of the implementation of this type of modulation in broadband systems.

Nowadays, it is possible to find several works on surface reconstruction with optical techniques that employ quality maps, all of them using laboratory cameras with several functions such as manual gain control, low value of white noise, etc. In this work we analyze the possibility to obtain a good 3D shape reconstruction using a webcam, with the aim to develop a low cost portable system. In this work, quality maps are designed to be implemented in the temporal phase unwrapping algorithm with fringe projection for 3D shape reconstruction. The combined techniques allow the noise suppression and the study of illumination areas obtained through fringe projection. In particular, threshold value of quality maps allows to select areas of high visibility in which the temporal phase unwrapping algorithm can be successfully applied. The effect of the position of projector, camera, and sample into the optical setup are considered in order to obtain the optimum fringe density and to suppress Moire or sampling effects in the area of interest. A low pass spatial filter, applied to the temporal phases, suppresses residual noise. The implemented camera calibration process demonstrates that image distortion at optimum spatial locations is negligible. The final 3D shape reconstructions show that the noise usually generated by shadows and dark areas of the specimen under study can be successfully eliminated.

We demonstrate the use of an area selective zinc in-diffusion technique as a simple and efficient technique for the fabrication of integrated photonic devices. In this work, the zinc in-diffusion process has a two fold application. It is well known that the diffusion of zinc in InP follows an interstitial-substitutional diffusion mechanism. This provides a concentration dependent diffusion profile, which allows us to control the sharpness of the diffusion front by controlling the background doping concentration of the semiconductor wafer. By controlling the zinc depth combined with a sharp diffusion front, the insertion losses of the devices can be minimized. In addition, this results in selective definition of p-n junctions across the semiconductor wafer and therefore offers the potential for integration with electronic devices. Using this technique an integrated 2x2 Mach-Zehnder modulator/switch was fabricated. The semiconductor wafer is based on InGaAsP multiple quantum wells. To selectively define p-n regions for the contacts, we use a 200-nm thick silicon nitride mask during the diffusion. The Mach-Zehnder structure is then patterned using photolithography and dry etching. After a cyclotene planarization process, p-type contacts are deposited on top of the diffused regions by evaporation and lift-off. Our experimental results demonstrate that on-chip losses on the order of 4-dB are obtained, which is significantly lower compared to the use of isolation trenches. The device response as a modulator requires an additional insertion loss of 3-dB for voltage controlled operation, with an extinction ratio better than 16 dB. In the case of electrical current operation, better than 20 dB extinction ratio was obtained with only 8 mA.

We report characterization of EIT resonances in the D1 line of Rb 87 under various experimental conditions. The dependence of the EIT linewidth on the power of the control field investigated. Strictly linear behavior between the ground levels as the main source of decoherence. We therefore formulated a new theory assuming pure dephasing to be the main decoherence mechanism. We also performed experiments where we created additional decoherence mechanisms by means of a counter-propagating repumper field. This field caused the ground-state population exchange, thus reproducing conditions in which the original theory is valid.

We demonstrate a quantum communication protocol that enables frequency conversion of quantum optical information in an adiabatic way. The protocol is based on electromagnetically induced transparency in sustems with multiple excited levels. The proof-of-principle experiment is performed using the hyperfine levels of the rubidium D1 line.

The effect of weak optical injection on the threshold gain and resonant frequency of index-coupled DFB semiconductor lasers is theoretically analyzed. The locking bandwidth modification due to injection is discussed for structures having different grating characteristics. Simple formulas are derived which allow comparison of the sensitivity to optical injection for DFB lasers and Fabry-Perot lasers. A symmetrical locking bandwidth is verified and a stability analysis for weak injection is also carried out, imposing a maximum limit of injection rate.

An alternative method to chromatography is reported to discriminate among white and aging tequilas. In a previous work we had reported a similar method to discriminate between 100% blue agave and mixed tequilas. A data base of 145 tequilas was created where well known tequila brands and tequilas in bulk were included. The bottled tequilas were purchased at various Mexican liquor stores to ensure that different batches of each brand were included in the data base. The method that we propose to discriminate tequilas may also be used for quality control in distilleries and, with the help of the data base, to identify counterfeit tequilas.