This PDF file contains the front matter associated with SPIE Proceedings Volume 7022, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Sub wavelength ripples (spacing < λ/4) perpendicular to the polarisation of the laser radiation are obtained by scanning a tightly focused beam (~1μm) of femtosecond laser radiation from a Ti:Sapphire laser (τ =100fs, λ =800nm & 400nm, f=1kHz) and from a Yb:glass fiber laser (τ =400fs, λ =1045nm, f=0.1-5MHz) over the surface of various materials like amorphous Nd:Gd₃Ga₅O₁₂ films 1 μm in thickness on YAG substrates, diamond, polytetrafluoroethylene, LiF, MgF₂, ZBLAN, Al₂O₃, LiNbO₃, SiO₂, Si, Cu and Au. The ripple patterns extend coherently over many overlapping laser pulses and scanning tracks. Investigated are the dependence of the ripple spacing Λ on the material, the lateral distance of the laser pulses, the N.A. of the focussing optics, the repetition rate and the applied wavelength. The ripples are characterised using electron microscopy. Some possible models for the origin of the ripple growth are discussed and conditions under which these phenomena occur are contained. New results concerning the scaling of the production process using a high repetition rate laser and a fast translation stage are demonstrated. Potential applications are presented and consequences for precise nano- and microstructuring using ultra short pulsed lasers are discussed.

Optical properties of different type of surface treatments of titanium biomaterial as polishing, grinding, and chemical etching are investigated in details. The main aim of this study is in sensing the organisation of nano-scale fibrinogen and oligonugleotides adhered on biomaterial surface. Thus permittivity change and the fluctuation in optical roughness of treated titanium surface, when titanium surface is subjected to the contamination of buffer fractions as well as to the contamination of human plasma fibrinogen fraction, are investigated through optical window of a cuvette by using diffractive optical element based sensor. During the progress of this work also optical ellipsometry as a corroborative method was used to verify the attachment of the molecules on the biomaterial surface.

This work is devoted to investigation of new photosensitizer Bacteriochlorin p N-methoxycycloimide oxyme methyl ester (BchlpOx-NOMe). Investigations of photosensitizer in vivo and experimental PDT were performed on animals bearing intramuscularly inoculated Erlich tumor and B16 melanoma. Characteristic absorption maximum of BchlpOx-NOMe around 795 nm is within the range of minimum intrinsic absorption of biological tissue. Dynamics and selectivity of sensitizer accumulation in tumor and normal tissue were estimated from spectra of absorption of sensitized tissue in vivo. The investigation has shown that the optimum time range to start PDT irradiation of tumor is 10-30 min after administration. Photosensitizer has shown high photodynamic efficiency of relatively large tumors, including high PDT efficiency in preliminary experiments with BDF1 mice bearing B16 melanoma, causing tumor growth inhibition more than 90% and prolongation of lifespan of tumor-bearing animals more than 60%.

The system of multi-spectral imaging of oxygen saturation is an instrument that can record both spectral and spatial information about a sample. In this project, the spectral imaging technique is used for monitoring of oxygen saturation of hemoglobin in human tissues. This system can be used for monitoring spatial distribution of oxygen saturation in photodynamic therapy, surgery or sports medicine. Diffuse reflectance spectroscopy in the visible range is an effective and extensively used technique for the non-invasive study and characterization of various biological tissues. In this article, a short review of modeling techniques being currently in use for diffuse reflection from semi-infinite turbid media is presented. A simple and practical model for use with a real-time imaging system is proposed. This model is based on linear approximation of the dependence of the diffuse reflectance coefficient on relation between absorbance and reduced scattering coefficient. This dependence was obtained with the Monte Carlo simulation of photon propagation in turbid media. Spectra of the oxygenated and deoxygenated forms of hemoglobin differ mostly in the red area (520 - 600 nm) and have several characteristic points there. Thus four band-pass filters were used for multi-spectral imaging. After having measured the reflectance, the data obtained are used for fitting the concentration of oxygenated and free hemoglobin, and hemoglobin oxygen saturation.

Photodynamic therapy (PDT) is one of the advanced methods of treatment of skin cancer and surfaces of internal organs. The basic advantages of PDT are high efficiency and low cost of treatment. PDT technique is needed for providing fluorescent diagnostics. Laser-based systems are widely applied to the fluorescence excitations for diagnostic because of a narrow spectrum of fluorescence excitation and high density of radiation. Application of laser systems for carrying out fluorescent diagnostics gives the image of a tumor distorted by speckles that does not give an opportunity to obtain full information about the form of a tumor quickly. Besides, these laser excitation systems have complicated structure and high cost. As a base for the development and creation of a video fluorescent device one of commercially produced colposcopes was chosen. It allows to decrease cost of the device, and also has enabled to make modernization for already used colposcopes. A LED-based light source was offered to be used for fluorescence excitation in this work. The maximum in a spectrum of radiation of LEDs corresponds to the general spectral maximum of protoporphyrin IX (PPIX) absorption. Irradiance in the center of a light spot is 31 mW/cm². The receiving optical system of the fluorescent channel is adjusted at 635 nm where a general spectral maximum of fluorescence PPIX is located. Also the device contains a RGB video channel, a white light source and a USB spectrometer LESA-01-BIOSPEC, for measurement of spectra of fluorescence and diffusion reflections in treatment area. The software is developed for maintenance of the device. Some studies on laboratory animals were made. As a result, areas with the increased concentration of a PPIX were correctly detected. At present, the device is used for diagnostics of cancer of female reproductive system in Research Centre for Obstetrics, Gynecology and Perinatology of the Russian Academy of Medical Sciences (Moscow, Russia).

Use of gold nanoparticles (NPs) as a contrast agent for medical imaging is shown to improve the efficiency of optoacoustic signal generation; this signal enhancement allows differentiation between different tissue types. This aspect of medical imaging is important when concerned early cancer detection. The present paper presents the results on the interaction process between the laser light and gold NPs, providing valuable information necessary for improved and more efficient NP synthesis. The attenuation of laser is studied for NP solutions of different geometrical characteristics and concentrations where the study is based on both optical and optoacoustic characterization techniques. First results show that the absorption and scattering are correlated by increasing the size of the nanoparticles between 5nm and 60nm. The optoacoustic signals we have been obtained demonstrate similar behavior for gold NP diameters of 5nm to 12nm.

Drilling holes with pulsed Nd:YAG lasers is well researched and state-of-the-art within a variety of industrial applications. Surgical needles in the medical field, turbine blades for the aviation industry, and gas filter for the automotive industry are just some examples that come to mind. Similar to other industrial developments over the last century this market asks for higher throughput, smaller diameter, higher aspect ratios, and of course within a minimum of tolerances. New laser sources and specially developed processes are entering the market to move the mere drilling to the next level of micro drilling. It is crucial to understand the application and the influence of the process parameters to develop a suitable, stable, and repeatable work process. Commonly used pulses within the microsecond-regime show a significant thermal side effect which is unacceptable if used e.g. in combustion nozzles. Reducing the thermal load by shortening the pulse length into the nanosecond-regime could be a compromise to bridge the gap between quality and production speed in high precision laser drilling. However, depending on the relation between pulse energy, pulse repetition rate, and "helical speed" a reduced, but existent, thermal effect is inevitable. The scope of this paper is to show the influences of the process parameters in helical drilling with a new developed nanosecond pulsed Nd:YAG laser at its fundamental wavelength of 1064 nm. A variation of drilling-optic principles in different materials are studied and the advantages as much as the disadvantages are discussed.

Result of Monte Carlo simulations of skin optical clearing is presented. The model calculations were carried out with the aim of studying of spectral response of skin under immersion liquids action and calculation of enhancement of light penetration depth. In summary, we have shown that: 1) application of glucose, propylene glycol and glycerol produced significant decrease of light scattering in different skin layers; 2) maximal clearing effect will be obtained in case of optical clearing of skin dermis, however, absorbed light fraction in skin dermis changed insignificantly, independently on clearing agent and place it administration; 3) in contrast to it, the light absorbed fraction in skin adipose layer increased significantly in case of optical clearing of skin dermis. It is very important because it can be used for development of optical methods of obesity treatment; 4) optical clearing of superficial skin layers can be used for decreasing of power of light radiation used for treatment of acne vulgaris.

Particles with typical dimensions higher than the light wavelength and relative refraction indexes close to one, scatter light mainly in the forward direction where the scattered light intensity has a narrow peak. For particulate media accomplishing these requirements the light scattered at small angles in a far-field detecting set-up can be described analytically by an effective phase function (EPF) even in the multiple scattering regime. The EPF model which was built for monodispersed systems has been extended to polydispersed media. The main ingredients consist in the replacement of the single particle phase function and of the optical thickness with their corresponding averaged values. Using a Gamma particle size distribution (PSD) as a testing model, the effect of polydispersity was systematically investigated. The increase of the average radius or/and of the PSD standard deviation leads to the decrease of the angular spreading of the small angle scattered light.

In this paper, we report theoretical description and first experimental observation of recently predicted phenomenon called optical orientation of local centers with permanent dipole moment. An electrical current arising at periodical modulation of the polarization of incident light was observed in a crystal of Bi₁₂SiO₂₀ grown in the argon atmosphere. Modulation frequency-dependence of the current amplitude allows us to attribute this current to the predicted effect. This deduction was additionally supported by our experimental data of light-induced dichroism and photoconductivity of the sample. Using a model of donor-acceptor pairs as dipolar centers we were able to explain features of optical orientation of dipolar centers in the crystal.

In this study we have focused on exploring the photoacoustic signal generated by laser induced dielectric breakdown process in pure water, under normal conditions. In this case the dielectric breakdown will lead to a formation of a shock wave. We investigated the relation between pulse energy and amplitude, group velocity and power spectrum of the shock wave. Also, the threshold for dielectric breakdown is estimated. A pulsed, high power Nd:YAG laser with λ = 532 nm and a pulse duration of 12 ns was used. The laser pulse energy ranges from 0.1 mJ to 7.4 mJ. Only photoacoustic signals generated from dielectric breakdown was considered. We found that the amplitude and the average group velocity of the shock wave correlates to the laser pulse energy. The frequency contents of the photoacoustic signal changes due to both non-linear behaviour and dissipative effects. We estimated the dielectric breakdown threshold to be 0.44 × 10¹¹Wcm^-2.

This study involves measurements of pulp consistency in cuvette and by an online apparatus, by innovatively scattering photoacoustic (SPA) method. The theoretical aspects were described at first. Then, a few kinds of wood fiber suspensions with consistencies from 0.5% to 5% were studied in cuvette. After that, a pilot of online apparatus was built to measure suspensions with fiber consistency lower than 1% and filler content up to 3%. The results showed that although there were many fiber flocks in cuvette which strongly affected the measurement accuracy of samples consistencies, the apparatus can sense fiber types with different optical and acoustic properties. The measurement accuracy can be greatly improved in the online style apparatus, by pumping suspension fluids in a circulating system to improve the suspension homogeneity. The results demonstrated that wood fibers cause larger attenuation of acoustic waves but fillers do not. On the other hand, fillers cause stronger scattering of incident light. Therefore, our SPA apparatus has a potential ability to simultaneously determine fiber and filler fractions in pulp suspensions with consistency up to 5%.

Holography allows one to record the amplitude and phase of a wavefront reflected from a three-dimensional (3D) object, and in principle has advantages for non-contact metrology applications. With digital holography, we use a digital camera instead of a holographic plate and reconstruct either numerically through simulated propagation or optically using a spatial light modulator. Digital holograms are in a convenient form for numerical processing and digital transmission, and recently digital cameras with sucient dynamic range and numbers of pixels have become available. This has raised interesting problems as to how the 3D data within digital holograms can be exploited and analysed. We present novel image processing techniques for the recording of wide-angle digital holograms and, for the purpose of object segmentation, the extraction of object surface profile information from such digital holograms.

This work reports a novel technique for demodulating fiber Bragg gratings subject to mechanical loading. The small wavelength shifts induced in the grating reflection spectrum of the fiber grating under loading caused the central or peak reflected Bragg wavelength to be displaced from its original position. A small percentage of the strain-induced spectrum from the fiber Bragg grating was then retro-reflected into the active cavity of the emitting laser diode where the optical feedback led to perturbation to the active cavity. An equivalent cavity model is also presented to validate the resulting modification to the emission properties of the laser device as measured by a photodetector integrated into the laser package, leading to sawtooth-like interference fringes typical of self-mixing interferometry being generated. Consequently, the embedded strain information contained in these fringes can then be extracted as a function of the applied loading strength and frequency to give the desired measurand without any complicated signal processing schemes. With the laser diode serving as the source and detector, a relatively simple and cost-effective scheme can thus be designed for interrogating fiber Bragg grating-based sensors for strain measurements.

In the quality inspection of wood materials, it is important to be able to detect knots and measure their dimensions automatically. Knots can be detected on the basis of their colour. A problem arises when the colour of the knot does not differ sufficiently from the surrounding area for a reliable measurement. To overcome this problem the tracheid effect can be used. As a result of the tracheid effect, a circular laser spot that is projected to the surface of wood is extended to an elliptical shape, the major axis of which is oriented in the direction of the wood grain. Since the grains surround knots, they can be detected by evaluating the orientation and eccentricity of individual laser spots. This paper discusses the suitability of the tracheid effect in the quality inspection of thin wood materials. In the course of this work measurements that utilize a laser spot line and an industrial camera are undertaken. An algorithm is developed for detecting and measuring the dimensions of knots. The performance of the algorithm and the measurement setup is evaluated on different knot types and sizes.

It is well known that back-reflections in single mode semiconductor lasers usually lead to line broadening and amplitude increase of noise. We will show that a particular choice of the laser bias, which we have called the crossover working point, is helpful to mitigate these effects. Starting the analysis using a self-mixing interferometer, we demonstrate a decrease of the disturbances as high as 40dB in the weak and moderate feedback regimes. We also extend the analysis for incoherent and coherent feedback for the case of high level of injection arising from an all-fiber setup. Two different semiconductor laser devices have been tested to verify the analysis predictions, with good agreement with experimental results.

A new method of high order broad-band optical interferometry is presented. The core concept is to use surface control of broad-band radiation with a complex, specially prepared spectrum. High order broad-band interferometers have several merits: selectivity along the line of sight, high noise immunity (and correspondingly high accuracy) and the possibility of carrying out precise measurements without mechanically moving the reference or test plates. These interferometers permit control of large aperture optical elements (including remote control) with nanometer and even subnanometer accuracy. Some application examples of high order broad-band interferometry are demonstrated.

In this review we present the analysis of optically pumped alkali lasers research and development from their first proposal in 1958 to the current state. Main achievements and problems existing in this field of research are discussed and possible solutions of the problems are proposed. Detailed description of the most important experiments and their results are presented. We have tried to provide an extensive list of references on this subject.

We developed a passively stabilized Kerr-lens mode-locking scheme for diode-pumped Yb-doped-bulk lasers. Taking an Yb:YAG laser as an example, we succeeded in generating pulses as short as 105 fs, which is to our knowledge the shortest pulse ever produced from a Yb:YAG laser. The spectral width and average laser power are 11.0 nm and 123 mW, respectively.

Metamaterials and photonic crystals are presented as the main approaches to achieve artificial negative refractive materials. Alone or associated with lithography techniques, femtosecond laser constitutes a potential tool for manufacturing negative refractive materials in the range from GHz to optical frequencies. Multi-photon photopolymerization of transparent materials and micro/nano-machining of metallic thin films are promising methods to obtain negative refractive photonic crystals and, respectively, metamaterials. Preliminary experiments of thin-film micro-machining using a femtosecond oscillator-amplifier laser are described. Further methods to improve the femtosecond laser machining are proposed.

We are developing a multi-kHz repetition rate high-average power Ti:sapphire regenerative amplifier as a pumping laser of a laser-plasma X-ray source. With an optimally designed ring resonator with a cryogenically-cooled laser rod, the average output power of 54 W before compression was achieved when pumped by a 180-W green laser at 10 kHz repetition rate. The focusability of the output beam was better than two times of the diffraction limit and can be compressed to 82 fs. Possibility of scaling to higher output power is discussed.

Two experimental methodologies for human skin optical non-invasive in-vivo assessment have been developed and clinically tested - imaging of the laser-excited autofluorescence fading rate, and simultaneous recording of the reflectance photoplethysmography signals at several laser wavelengths with different skin penetration depths. Details of both equipments are described along with some measurement results illustrating feasibility of the novel technologies.

In this paper welding seam imaging in a very narrow and deep groove is presented. Standard camera optics can not be used as it does not reach the bottom of the groove. Therefore, selecting suitable imaging optics and components was the main challenge of the study. The implementation is based on image transmission via a borescope. The borescope has a long and narrow tube with graded index relay optics inside. To avoid excessive heating, the borescope tube is enclosed in a cooling pipe. The performance of the imaging system was tested by measuring its modulation transfer function (MTF) and visually evaluated its distortion. The results show that a borescope providing VGA resolution is adequate for the application. The spectrum of the welding processes was studied to determine optimum window to observe the welding seam and electrode. Optimal bandwidth was found in region of 700nm-1000nm.

This paper discusses an image sharpness-based range sensing method and its applicability to the thickness measurement of paper materials. This method comprises a camera tilted at a known, non-orthogonal angle above the surface to be measured. From the image formed, it is possible to estimate the most focused row by summing the gradients inside each row. When images are taken simultaneously from two surfaces (i.e. reference surface and material surface), the thickness of a material can be determined by calculating the difference between the best focused rows. The suitability of the method to the thickness measurement of paper materials is evaluated by linearity measurements using different measurement configurations and different paper samples.

We present a novel approach that enables online, real-time and non-contact measurements of thickness of protective coatings. The proposed technique based on spatial filtering of dynamic speckles generated by rapidly deflected laser beam. An advantageous feature of the technique is that it is capable for very fast measurement of coating thickness with accuracy of one micrometer while their roughness is 20 μm or higher. Such a high performance is achieved due to proper consideration of statistical properties of spatially filtered dynamic speckles. In this paper we report experimental study of correlation properties of photodiode responses in different configurations of optical setup. The results are in good agreement with theoretical estimations. Performance of a laboratory prototype of the proposed sensor is demonstrated in application to profile measurements of a tube coated by protective layers of different thickness.

Improving end product quality, minimizing the manufacturing costs and maximizing the yield in wood industry, an accurate, high speed and non-contacting measurement method for measuring thin wood thickness variations is required. Optically homogeneous materials have been measured successfully with laser triangulation for decades; however, non-homogeneous and porous target materials, such as wood, are more complicated to measure with high accuracy. The light scattering in wood is strongest in the parallel direction of wood grain cells shaping the originally round laser spot into an elongated form (tracheid effect). This study is focused on discovering an optimal sensor head orientation with respect to the elongated spot, comparing two different sensor technologies, testing how surface roughness affects on thickness measurements and determining the optimal laser wavelength range for measurement of wood thickness. The main sources of measurement uncertainty for laser triangulation in the measurement of thin wood thickness are also discussed. The results suggest that the laser triangulation plane should be aligned perpendicular to the grain direction and the wavelength of light around 550 nm might be optimal choice in order to minimize the measurement error.

The analytic schemes of calculated absorbed and scattered radiation spatial distribution in multilayer plant and living tissues and diagnostic of their physical state are presented. The correct realization of these tasks was obtained with 3D Monte Carlo simulation of optical radiation propagation through multiple scattering medium in TracePro environment. Analysis of simulation data was made by differential backscattering method, which allows to investigate general backscattered radiation dependences on optical and geometrical parameters of living tissue. It was shown that obtained results formed the basis for developing an algorithm of optical superficial inhomogeneous registration and spatial localization. Such diagnosis can be executed in tissues of any arbitrary surface structure. Designed scheme is intended to utilize in contactless macro diagnostics device. The same approach was used for simulation of optical spectra of healthy and diseased virtual leaves for plant tissue pathological changes revealing.

The main objective of this study was to construct a double integrating sphere system and to verify its performance using Intralipid fat emulsion. The final goal was to be able to determine optical properties of various turbid suspensions with the proposed system. Online measurements even would have been possible as backscattering and forward scattering were measured simultaneously. The measured suspension was injected in a cuvette placed between two integrating spheres and illuminated with a laser through the first sphere. The diameter of the spheres was 8" and the diameter of the sample port could have been varied up to 2.5". The cuvette was made of plastic and optical grade glass and its diameter was sufficient to cover the sample port area. The sample thickness in the measurement cuvette was 5 mm. Optical powers were detected using fiber coupled photodiodes. There was one diode for each sphere and one for the unscattered light at the opposite end of the sphere system facing towards the laser. The measured optical powers were converted to absorption coefficient, scattering coefficient and if possible to anisotropy using an inverse adding-doubling method. The results measured for the Intralipid using the described system corresponded with those documented in published literature. A number of pulp samples with unknown optical properties were measured with encouraging results. However, the differences between different pulps and fillers are so small that, in the future, the focus will be in error source elimination to achieve reasonable accuracy.

In vivo experimental results of plant tissue properties kinetics are presented. It is shown that the method of differential backscattering can serve for estimation of the physiological state of the plants, as evidenced by results of mathematical modeling.

Using two physical methods (Rayleigh light scattering and Dynamic light scattering), the effect of cooper and cadmium, toxic heavy metals, on proteins in water solutions (including blood serum proteins) was studied. A physical mechanism of interaction between heavy metal ions and charged biopolymers which is based on formation of strong bonds of metal ions with the surface of macromolecules is discussed. Based on the results obtained, a method to monitor natural liquid media pollution with heavy metals is proposed.

Dynamic light scattering is used to measure molecular parameters of collagen in solutions. Using photon correlation spectroscopy we obtained the dependences of the translational diffusion coefficient on pH in water and salt solutions. Supermolecular aggregates formation was found in salt solutions (with KCl and Pb(CH₃COO)₂).

The feasibility of the time-of-flight (TOF) technique application at the wavelength of 820 nm for the sensing the changes in optical properties of multilayered scattering medium is considered. The TOF signals from a 3-layer biotissue phantom consisting of two skin layers and a blood layer between them are obtained by using the Monte Carlo method for various values of glucose content. Glucose level variations in the physiological range of concentrations are supposed to induce changes in the optical properties of the blood-like layer and the bottom skin-like layer of the considered 3-layer phantom. Different characteristics of the obtained TOF signal are analyzed. Relative changes in the signals induced by the glucose level variations are analyzed for different source-detector separations. It is shown that the maximal relative change of the pulse energy corresponding to the glucose concentration change from 0 to 500 mg/dl is about 7%; however, the application of the time gating technique allows to increase this sensitivity up to 12 %. The sensitivity maps allowing to determin the optimal position and size of the time gate are obtained for five values of the source-detector separation.

The main goal of this work is to develop a fast tool for calculation of light scattered by single large optically soft spheroidal particles. In particular, such particles mimic biological cells (e.g., red blood cells (RBC)). Methodology of calculation of light scattering by arbitrarily oriented optically soft spheroidal particles in Ray-Wave Approximation (RWA) is presented. We show that RWA permits to quickly and accurately calculate the angular distributions of the intensities of light scattered from particles mimicking RBC.

Carbon-based materials exhibit unique properties driven by the many different bonding configurations available to the element carbon. Many of them proved to be compatible with inorganic and/or biologic systems and might be considered as useful materials in medicine and biology. The carbon nanoparticles existing in environment are an important factor on healthy, either by their toxicity or by interaction with pathogen microorganisms, Carbon black is nowadays one of the additive most widely used to make composites and the applicability of nanocarbon-based composites depends on how well its properties can be manipulated. The activation of carbon materials improves their functional properties and depends on their structure. Through the variation of the experimental parameters, the method of laser-induced pyrolysis allows obtaining carbon nanoparticles with different morphologies providing useful functional properties. The focus is to drive these materials into a regime where they can naturally interface with the surrounding matter. With other words, the goal of the work is to investigate how to modulate, through laser induced pyrolysis, the characteristics of carbon nanopowders in order to achieve functional properties claimed by specific applications.

The work was performed to estimate the influence of liposomal size distribution on the level and selectivity of accumulation of photosensitizer of near-IR spectral range Tiosens (liposomal form of aluminium hydroxide phenylthiophthalocyanine) in tumor. Tiosens liposome dispersions were prepared using classic Bangham procedure. Particle size was reduced and unified using Avanti Mini-Extruder equipped with Nucleopore membranes and high-pressure homogenizer Donor-1. Liposomal size distribution was determined by means of laser correlation spectroscopy. Dynamics and selectivity of Tiosens accumulation in Erlich tumor were measured in vivo using fluorescence spectroscopy. It was shown that level and selectivity of accumulation of liposome-encapsulated drug is determined mostly by content of small-sized fractions, while fractions of larger size are quickly cleared from blood by RES and not contribute in photosensitizer accumulation.

In this paper, we investigate the effect of nanoparticles made of different materials, such as titanium dioxide (TiO₂), silicon (Si), and silica (SiO₂) on UV protective properties of transparent emulsion used for sunscreens within the range of diameters d=10-200 nm by means of Monte Carlo simulations. As a result, silicon nanoparticles of appropriate sizes are the most protective-efficient within the whole UV spectral range among all kinds of investigated particles. Within one kind of particles, specific sizes are the following. For shorter wavelengths of the considered range (λ = 290 nm) 20-100-nm TiO₂ and 30-100-nm Si particles are the most effective protectors. For longer wavelengths (350 and 400 nm) the most pronounced attenuation is obtained with: a) for Si: d = 40 - 120 nm (λ = 350 nm) and d = 60 - 140 nm-sized (λ = 400 nm) particles, b) for TiO₂: d = 80 - 160 nm (λ = 350 nm) and d = 120-180 nm-sized (λ = 400 nm) particles. Silica particles are much less protective than those mentioned above due to small refractive index mismatch between them and the surrounding emulsion.

High-resolving full-field OCT method is considered that provides increased resolution and interferometric data acquisition speed due to high optical magnification and electronic lateral scan provided by video camera. OCT data processing algorithm based on signal squaring with subsequent low-pass filtering is considered. Experimental results obtained when evaluating samples of paper material are presented and discussed.

A Monte Carlo method for holistically simulating optical coherence tomography (OCT) has been developed. The geometrical optics implementation of OCT probe optical system was combined with Monte Carlo simulation for photon propagation in homogeneous turbid media to simulate OCT signal. The hyperboloid model to describe Gaussian beam's photon propagation made the simulation more accurate, and the importance sampling method has been used to accelerate the simulation process. We made the experimental measurements and simulations for Intralipid^TM samples with different concentrations. Both the measured and simulated results show that the high scattering coefficient and weakly forward scattering are the primary causes for the attenuation of OCT signal as the focusing depth increases, and the OCT imaging resolution also decreases with the increase of focusing depth. The focusing plane curvature caused by scanning the fibretip laterally near the front focal plane of the OCT probe optical system deforms the OCT image and results in the decrease of image resolution also. It is also found that the effect of the numerical aperture (NA) of the fibretip on OCT signal depends on the value of NA. For a given OCT probe optical system, there is a best numerical range for NA.

Non-invasive measurement of paper porosity is an important problem for papermaking industry. Presently used techniques are invasive and require long time for processing the sample. In recent years optical coherence tomography (OCT) has been proved to be an effective tool for non-invasive study of optically non-uniform scattering media including paper. The aim of present work is to study the potential ability of OCT for sensing the porosity of a paper sample by means of numerical simulations. The paper sample is characterized by variation of porosity along the sample while numerical simulations allow one to consider the samples with constant porosity which is useful for evaluation of the technique abilities. The calculations were performed implementing Monte Carlo-based technique developed earlier for simulation of OCT signals from multilayer paper models. A 9-layer model of paper consisting of five fiber layers and four air layers with non-planar boundaries was considered. The porosity of the samples was varied from 30 to 80% by varying the thicknesses of the layers. The simulations were performed for model paper samples without and with optical clearing agents (benzyl alcohol, 1-pentanol, isopropanol) applied. It was shown that the simulated OCT images of model paper with various porosities significantly differ revealing the potentiality of the OCT technique for sensing the porosity. When obtaining the images of paper samples with optical clearing agents applied, the inner structure of the samples is also revealed providing additional information about the samples under study.

The basic aim of this study was to analyze the frequency spectrum of photoacoustic signals generated in Intralipid and water. Intralipid, which is a well-known tissue simulating phantom, was used with concentrations of 1 % and 2 %. Some of the experiments involved the addition of glucose (5000 mg/dl). Measurement results demonstrated that, at 1064 nm, the intensity of the obtained spectra is higher in water than in Intralipid. Also the shapes of the acoustic spectra measured for water and Intralipid were dissimilar. The relative part of low-frequency components was found to be larger in Intralipid than in water. On the other hand, a clear intensity maximum was found in the frequency spectrum of water, whereas in Intralipid, intensity decreased towards higher frequencies from a maximum of less than 0.5 MHz. Moreover, water had a wider and smoother photoacoustic signal spectrum. 1 % and 2 % Intralipid concentrations differed mainly in terms of acoustic wave amplitude, while glucose had a negligible effect on the acoustic spectra of these solutions. The calculated spectral moments, namely, variance of the power spectrum, skewness and kurtosis, were no better indicators for glucose than the peak-to-peak value.

This paper presents the performance of centroid determining algorithms for the ideal Gaussian stripe and Gaussian spot with added external noise. In the Gaussian spot case, for the binary images, centroid calculation was performed using weighted mean method. Morphological operations were used to filter out possible shape distortion, holes formation and scattering effects caused by the external noise. In case of grayscale images the method of calculating the centroid through Gaussian fitting curves was used and its accuracy visualized. In the Gaussian stripe case, a stripe was analyzed with different noises levels and with sub pixels shifting.

The aim of this study was to discover possibilities for using x-ray radioscopy in thin wood inspection. The main goal was to find a suitable x-ray imaging method to define the variations in wood density. In x-ray imaging radiation is sent through an object where radiation weakens proportionally to the object's thickness, density and moisture content. By sensing differences in attenuation an image can be created, allowing for the study of these properties. Because x-rays can penetrate deeply, x-ray imaging can be used for various materials and for many different imaging applications. The energy level of x-ray must be fairly low when imaging thin wood, as the level of attenuation is low due to the wood's thinness and low density. Some different imaging devices were tried in order to find suitable method for the task, and the best quality images were obtained with a mammography x-ray device. Digital out processing was used to enhance image contrast and density variations, respectively.

A laser strainmeter for in-situ monitoring of an important actively seismic area of Europe, namely Vrancea region in Romania is proposed. Six groups from four different countries (Romania, Czech Republic, Italy and Greece) with various areas of expertise (e.g. geophysics, lasers, optics, interferometry, and mechanics) are involved in order to sustain the complexity of the project. This paper presents some preliminary laboratory experiments related to measuring relative displacements with a stable interferometer. Displacements of the order of tens to hundreds of nanometers (80 to 285 nm) were measured with uncertainty of ±1 nm. A computer algorithm was used to process the interferograms.

This paper introduces a way to apply Time-of-Flight (TOF) 3D camera in volume measurement for a stockpile. Two methods, passive and active (reflector based), were used for measuring volume. In the volume calculation algorithm, Delaunay triangulation was applied. This paper also discusses characteristics of the camera and therefore accuracy of the system.

Two different paper grades were tested with a clearing agent to measure how much mechanical smoothening can improve transparency inside paper. The paper grades were newsprint and supercalendered paper. The paper furnishes of both papers were alike, but the supercalendered paper was mechanically smoothened. Anise oil was used as the clearing agent, but similar measurements were also done with air and water. Black lines 8.5 μm to 281.1 μm wide were placed behind layers of cleared paper and transparency was measured with a microscope. When anise oil was the clearing agent, supercalendering improved transparent paper grammage from 139 g/m² to 164 g/m². With water the improvement was from 40 g/m² to 51 g/m². With air the improvement was not determinable. As a conclusion, it is recommended that paper is smoothened if it needs to be studied optically. Optical coherence tomography, for example, would benefit from this treatment.

A compact near-diffraction-limited picosecond microchip oscillator-amplifier system was developed. When pumped by 0.9-W average power pulsed radiation, the microchip generated 9-μJ energy pulses of 400-ps duration at 1-kHz rate, in a nearly TEM₀₀ transversal mode (beam quality factor, M² < 1.1). The microchip output was amplified up to 12-mJ pulse-energy at 1-10 Hz repetition rate in a two-pass flash-pumped Nd:YAG amplifier. We used the 1064-nm output beam for nonlinear conversion to 532-nm second harmonic (SH) and 266-nm fourth harmonic (FH). The pulse-energy of SH and FH output was 6-mJ and 1.6-mJ, respectively, which corresponds to 50 % and 13 % conversion efficiency.

The study of correlation between hardness of aluminum alloys and properties of laser plume are presented in this article. The negative relationship between opto-acoustic signal or crater volume and hardness was observed. It was found at the first time that the mechanical properties of analyzed sample correlate with ablated mass quietly different during laser crater formation. The temporal evolution of laser plume emission in dependence on hardness of alloys are studied as well as. So, the temperature calculated by lithium transition strongly depends on hardness, while the temperature for aluminum does not correlate with properties of alloys. It is supposed to use opto-acoustic signal and Al I emission signal either for correcting the interferences from sample matrix or for controlling the hardness of alloy during its heat hardening.

The anomalous behavior of laser plume temperature was observed in this work after evaporating annealed ceramics. This circumstance allows sorting annealed and non-annealed lithium ferrites which contain the same phase of LiFe₅O₈ by LIBS. The correlation between both optoacoustic signal and emission signal of matrix element and ablated volume is studied as well as. It was found linear dependence of optoacoustic signal on crater volume, but iron emission depended on volume non-linearly. Therefore, optoacoustic is preferable for correction of experimental condition changes during analysis of those samples by methods with laser ablation.

We present an effective solution for an all-polarization-maintaining modelocked femtosecond fiber laser operating at the central wavelength of 1028 nm. The laser is based on an Yb-doped active fiber. Modelocking is enabled by a semiconductor saturable absorber mirror, and the central wavelength is enforced by a fiber Bragg grating. The laser is self-starting and demonstrates excellent stability against Q-switching. Pulse energies reach 13 nJ at 34 MHz repetition rate. External compression leads to near transform-limited pulses of 140 fs.

The objective of this paper is to analyze two marking laser systems and to discuss the possible industrial applications of laser techniques; the first uses a diode pumped Ytterbium fiber laser and the second a pumped flash light Nd:YAG. Starting from the phenomena of heating due to laser irradiation and the spatial profile of deposited energy we try to explain the marking technique, including the laser-assisted coloring by studying the dynamics and the evolution of the parameters involved in this process. Also we emphasize the industrial importance of the laser possibilities compared to classical methods.

Vanadium dioxide thin films were prepared on r-plane sapphire substrates by using in-situ pulsed laser deposition (PLD) and by post-annealing pure metallic vanadium films in synthetic air atmosphere by varying the annealing temperature and annealing time. As a result, vanadium oxide thin films with various compositions were produced. Thin films produced by using PLD contained also pure VO₂ thin films, while post-annealed films had mixed phase structure of metallic vanadium and vanadium oxides or only different vanadium oxides. SPM surface analysis showed that pulsed laser deposited films were very smooth with R_q < 16.7 nm. The magnitude of metal-insulator transition (MIT) of the optical transmission measured from pulsed laser deposited VO₂ thin films was around 50% at the wavelengths of 1.5 and 2.5 μm. Surface roughness of the post-annealed films was high, R_q < 86.1 nm. Although the post-annealed films were non-homogenous phase mixtures containing very little VO₂ phase in their structure, some of them showed very good optical responses at IR-wavelengths. At the wavelength of 2.5 μm, optical transition between insulator and conductive states as large as 74% was measured.

A proposed approach for quantitative analysis of samples by laser induced breakdown spectroscopy was used for composition determination of Al alloy samples. Disproportion between composition of laser plasma and bulk sample is explained by selective evaporation of components during melting - evaporation stage. Effect of Batanov - Bunkin - Prohorov - Fedororov transparent wave during laser ablation was accounted by proposed approach. Spectra correction method was successfully used for analysis of Al alloys samples.

Modal analysis methods are relatively recent methods developed in order to exploit the dynamical models of real mechanical structures (such like airplanes) and to estimate their transfer functions. Self Mixing (SM) sensors were previously used in modal analysis applications using essentially a frequency sweeping of a sinusoidal signal requiring thereby very long time and complicated signal processing (Kalman filters, ...). The method used in this article consists of an excitation with a white noise requiring a sensor with an output that is a real image of the vibration itself in order to have a response for the whole frequency spectrum. This may be achieved with strong feedback SM sensors where it is demonstrated that with a sufficiently high coupling the Output Optical Power (OOP) of the laser follows exactly the displacement of the target. This method has the advantage of estimating the transfer function over the whole frequency spectrum with only the need of a FFT analyser and not any other signal processing.