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A variety of compensated Distributed feedback (DFB) lasers have been extracted by simulation using the laser rate equation description of a DFB laser. Here preselected desired system performance estimates are used as target measurements to extract physically realizable laser parameters for an intensity modulation direct detection (IM-DD) subcarrier multiplexing (SCM) optical link to offer a promising improved system performance. The resulting DFB laser models have favourably low threshold current and narrow line widths and have the capability of IMD and HD correction along with RIN and clipping distortion suppression.

The paper reports on immediate effects of pulsed laser operating at 532 nm and fluences below 2.5 J cm –2 on soiled cellulose. The degree of polymerisation was determined viscometrically, while diffuse reflectance FTIR was used to gain insight into the changes in the chemical composition. Although no detectable immediate changes were observed after treatment of paper with laser beam at 532 nm, the irradiation of paper containing carbonaceous dirt resulted in significant discoloration of the treated substrate. The possible reasons for the extensive formation of yellow chromophores are discussed.

In this paper, we report the results of analytical and experimental studies of the characteristics of a high-brightness laser-diode end-pumped Nd: YVO4/KTP laser. A simple model was developed to optimize the cavity parameters and to estimate the green output power of intracavity-frequency-doubled lasers. Using a 1-W high-brightness laser-diode as the pump source, high-efficiency operation was realized based on the optimized cavity design. The second-harmonic output power at 532 nm was measured to be 286.5 mW at an incident pump power of 881.4 mW, corresponding to an optical-to-optical efficiency of 32.5 %.

In a frequency-shifted feedback (FSF) laser, an intracavity light field is frequency-shifted beforebeingrecirculated through a gain medium. The FSF operation is obtained by placing an acousto-optic modulator inside the cavity and closing the cavity by the first order diffracted light of the modulator. The intracavity frequency shift prevents an evolution of a standing wave in the cavity and the laser output exhibits a very unique spectral feature. In this paper, the spectral output of the FSF laser is examined by use of a diode-pumped Nd: YVO4 as a gain medium. A theoretical treatment of the FSF behavior is also discussed. It is shown here that the FSF laser output has spectral output called “chirped frequency comb” with an ultrafast frequency chirp rate of several hundreds of PHz/s.

Macroscopic fiber orientation angle is known to affect stack lean of paper (e.g. z-fold continuous form) and a lot of research have been devoted to control macroscopic fiber orientation. But little attention has been paid to microscopic fiber orientation. The objective of this work is to clarify the relationship between microscopic and macroscopic fiber orientation and to obtain any hint or clue in controlling fiber orientation. The distribution of fiber orientation angle for nine kinds of wood-free paper was evaluated by both laser diffusion technique and ultrasonic elasticity measurement. The main difference between these two method is magnitude of the area subjected for measurement ; the area of the former method is much smaller than same of the latter. Therefore, results of the former method were thought to represent microscopic fiber orientation and of the latter macroscopic fiber orientation. By comparing the fiber orientations obtained with these two methods, the relationship between microscopic and macroscopic fiber orientation could be found. The results are summarized as follows : (1) The correlation coefficient between microscopic and macroscopic fiber orientation angles for the same sample position varies paper to paper.(2) If the variation of fiber orientation angle for cross-machine direction is large, the correlation coefficient between microscopic and macroscopic fiber orientation angles becomes large.(3) The paper which has larger variation of microscopic fiber orientation angle along machine direction shows poor correlation between microscopic and macroscopic fiber orientation angles.(4) Sheet formation seems to affect uniformity of fiber orientation angle along machine direction.

The main physical principles of the operation of ring gas lasers in the laser-gyroscope regime are examined. The influence of nonreciprocal effects on the operational parameters of ring gas lasers and the methods of controlling, with the aid of the nonreciprocal magneto-optical Zeeman effect, the parameters of these lasers used in gyroscopes are discussed.

In this paper, we report on a method for fabricating an inexpensive microfluidic platform on parchment paper. Parchment paper was selected for this purpose due to its wide availability for culinary applications and hydrophobic silicone-based surface coating. We were able to selectively modify the surface structure and property (hydrophobic to hydrophilic) using a CO2 laser. The modified surface has highly-porous structure which helps to trap chemical and biological reagents for analysis. The treated surface is stable over time and can be used for aqueous droplet assembly. Finally, we demonstrated the applicability of this platform for performing chemical reaction using luminol-based hemoglobin detection.

Development of short-wavelength semiconductor lasers had made a large contribution to the realization of high density optical memories. For example, InGaAlP red lasers have been used as light sources for high capacity optical disc systems (DVD). The next-generation, high definition DVDs will require a furthershortning of laser oscillation wavelength into the blue-light region. This paper reviews recent developments in short-wavelength semiconductor lasers and describes some of the device characteristics related to the optical memory applications.

The remarks on the results published in [1–4] on the simulation of a copper vapour laser with hydrogen admixtures are analysed. It is shown that these remarks do not affect the conclusions made in our papers, and many of them are simply erroneous.

Laser-induced fluorescence imaging has been used to study the microstructure of paper surfaces. Pulses from a XeCl-excimer laser, 10 ns in duration at 308 nm, were used for excitation, and fluorescence was collected at 420 nm. The excitation spot diameter was approximately 20 µm, and the sampling interval 0.15 mm. Within an area of 5*5 mm2, 1023 sampling points were recorded to generate 3D fluorescence maps of paper surfaces. Papers containing fluorescence whitening agents (FWAs) gave the highest average fluorescence signals. Coated papers with no FW As show weaker signals than the base sheet. For some thirty different paper samples, an obvious correlation between the amount of coating and the average intensity of the fluorescence signal was observed. Signal fluctuations around the average intensity values were sensitive to (1) the chemical pulp content in super calantered (SC) paper, (2) the amount of recycled fiber in newsprint, and (3) the amount of coating on the light-weight coated (LWC) paper surface. An effort was made to correlate fluorescence imaging results to predict mottling (diffusion of printing ink after printing) in various paper brands.

A conventional problem of paper handling in a page-printing printer is to design a reliable paper path. Sometimes, this also affects the printing quality. The nonlinear theory of elastica has often been used to model paper deflection shape and to predict the paper path between some guiding rollers. The present paper proposes another method that can solve this problem more efficiently. Considering a piece of paper as a nonlinear beam, finite element analysis with geometric nonlinearity and manipulating the contact gap element between paper and guiding surfaces can be used to simulate the large-deflection behavior of paper. In this paper, the paper path in the vicinity of an OPC (organic photoconductive) drum is investigated with a general purpose finite element package. The effect of the electrostatic force between the OPC drum and the paper is considered, and the deformed shape of the paper for different forces lengths is obtained. According to those results an appropriate paper guide is added for an exact paper path.

Lasers can provide a precious tool to conservation process due to their accuracy and the controlled energy they deliver, especially to fragile organic material such as paper. The current study concerns laser modification such as paper cleaning, initially of test papers artificially soiled and then of an original book of the early 20 th Century. The test objects were A4 copier paper, newspaper, and paper Whatman No.1056. During the experiments, ink of a pen, pencil and ink from a stamp was mechanically employed on each paper surface. Laser cleaning was applied using a Q-switched Nd:YAG operating at 532 nm and CO 2 laser at 10.6 μm for various fluences. The experimental results were presented by using optical microscopy. Eventually, laser cleaning of ink was performed to a book of 1934, by choosing the best conditions and parameters from cleaning the test samples, like Nd:YAG laser operating at 532 nm.

We have developed a novel prototyping method that utilizes animated paper, a versatile platform created from paper and shape memory alloy (SMA), which is easy to control using a range of different energy sources from sunlight to lasers. We have further designed a laser point tracking system to improve the precision of the wireless control system by embedding retro-reflective material on the paper to act as light markers. It is possible to change the movement of paper prototypes by varying where to mount the SMA or how to heat it, creating a wide range of applications.

An important requisite for the forensic analysis of inks on documents is that damage to the document is avoided or minimised. This paper describes a technique for dye identification in ballpoint pen inks using LDI-TOFMS on single ink bearing paper fibres and its application to a case. A single ink bearing paper fibre can be prised from the surface of the document under a stereo microscope and presented to the instrument for analysis without further treatment. This sampling process causes imperceptible damage to the surface of the document. Clear mass spectrometric identification of the ink dyes is obtained. A case example is provided to illustrate the practical application of the technique.

Laser technology has been developed for cutting of paper materials since the middle of 1970’s. Due to high cost of equipment and maintenance the laser technology has been applied in paper industry only in 1990’s. During its development in the field of processing with different wood-based materials laser technology was confronted with problem of color change in the area of interaction between laser beam and paper material. The main problems in laser cut paper are yellowing and carbonization of the cutting edge. It is commonly known that lignin is the main cause of color change. Due to its optical characteristics lignin is a good absorber of light of various wavelengths compared to other wood compounds like cellulose and hemicelluloses. But structure of lignin is still unresolved nowadays and only few studies concentrate on the phenomena of interaction between laser beam and paper material.The aim of this study was to clarify the nature of color change of the samples which were exposed to influence of light with different wavelength. CO2 laser was employed to carry out cutting of paper material samples. This choice was caused by its high suitability for cutting of wood based materials. CO2 laser operated with wavelength of 10600 nm which is easily absorbed by paper material. The experimental part covers measurement of optical characteristics of the samples after laser cutting as well as during storage time of 21 days. The effect of laser parameters, such as laser power and cutting speed, was considered.Laser technology has been developed for cutting of paper materials since the middle of 1970’s. Due to high cost of equipment and maintenance the laser technology has been applied in paper industry only in 1990’s. During its development in the field of processing with different wood-based materials laser technology was confronted with problem of color change in the area of interaction between laser beam and paper material. The main problems in laser cut paper are yellowing and carbonization of the cutting edge. It is commonly known that lignin is the main cause of color change. Due to its optical characteristics lignin is a good absorber of light of various wavelengths compared to other wood compounds like cellulose and hemicelluloses. But structure of lignin is still unresolved nowadays and only few studies concentrate on the phenomena of interaction between laser beam and paper material.The aim of this study was to clarify the nature of color change of the samples which were exposed to influence of light...

At present, the topic of automated vehicles is one of the most promising research areas in the field of Intelligent Transportation Systems (ITS). The use of automated vehicles for public transportation also contributes to reductions in congestion levels and to improvements in traffic flow. Moreover, electrical public autonomous vehicles are environmentally friendly, provide better air quality and contribute to energy conservation. The driverless public transportation systems, which are at present operating in some airports and train stations, are restricted to dedicated roads and exhibit serious trouble dynamically avoiding obstacles in the trajectory. In this paper, an electric autonomous mini-bus is presented. All datasets used in this article were collected during the experiments carried out in the demonstration event of the 2012 IEEE Intelligent Vehicles Symposium that took place in Alcalá de Henares (Spain). The demonstration consisted of a route 725 metres long containing a list of latitude-longitude points (waypoints). The mini-bus was capable of driving autonomously from one waypoint to another using a GPS sensor. Furthermore, the vehicle is provided with a multi-beam Laser Imaging Detection and Ranging (LIDAR) sensor for surrounding reconstruction and obstacle detection. When an obstacle is detected in the planned path, the planned route is modified in order to avoid the obstacle and continue ist way to the end of the mission. On the demonstration day, a total of 196 attendees had the opportunity to get a ride on the vehicles. A total of 28 laps were successfully completed in full autonomous mode in a private circuit located in the National Institute for Aerospace Research (INTA), Spain. In other words, the system completed 20.3 km of driverless navigation and obstacle avoidance.

Strong demand exists for a non-contacting paper caliper measurement which can be used as an input to a paper thickness control system. Caliper sensors requiring sheet contact suffer from errors related to dirt or coating build up and from high maintenance costs related to wear. These sensors can also damage the product by picking holes and marking sheets. Details of an on-line measurement device which employs two opposed laser displacement sensors and an inductive displacement sensor are presented. The sheet is held perpendicularly to the sensors with a Coanda air clamp. Dust and temperature control features which enable the sensor to operate reliably in an industrial environment are discussed. Results of production trials of this sensor are presented. Sub-micron profile agreement to lab and contacting caliper measurements has been demonstrated on light sheets. Results are presented of measurements on a wide range of paper grades from coated and uncoated light sheets to coated board.

Online measurement of paper thickness profile is essential in paper production. For decades paper thickness has been measured online with sensors that are contacting the web on both sides. In 2005 a new optical online paper thickness gauge was introduced which only contacts the web on the other side. The sensor is based on a laser triangulation sensor and a magnetic sensor, and it determines the paper thickness from the difference of the two measurements. For calibration of the two sensors, a robust concept has been developed which utilizes the measured object and takes place in the measuring environment so that the calibration is automatically adjusted to the current measuring circumstances. More importantly, with the presented method the non-linearity of the laser sensor is cancelled enabling the measurement of the thickness profile shape with an accuracy much better than that of the laser sensor. Profile accuracy of 0.5 μm (2σ) has become normal while the measuring range is often several hundreds of microns and the measuring distance to the paper web 1.0-1.5 mm with a laser sensor having linearity of ±2 μm.

An experimental set-up was devised to record the transmission of red and green HeNe lasers through different types of paper. The measured data was compared with data obtained using the Henyey-Greenstein function (often employed in paper optics models to represent the bulk scattering of material samples) and data obtained using an alternative exponentiated cosine function. The comparisons are used to qualitatively assess the degree of fidelity of the bulk scattering approximations provided by both functions.

Passively Q-switched Nd: YAG microchip lasers are robust, compact, economical, all-solid-state sources of coherent, subnanosecond, multikilowatt pulses at high repetition rates. These diminutive, quasi-monolithic devices produce pulses as short as 218 ps, pulse energies up to 250μJ, and peak powers up to 565 kW. The high output intensities enable the construction of extremely compact nonlinear optical systems. The short pulses are useful for high-precision ranging using time-of-flight techniques. The short pulse durations and ideal mode properties can also be used to advantage in the characterization of materials. When focused, the output intensities are sufficient to photoablate materials, with applications in laser-induced breakdown spectroscopy and micromachining. The ultraviolet harmonics of the microchip laser have been used to perform fluorescence spectroscopy for a variety of applications. Systems based on the passively Q-switched microchip lasers, like the lasers themselves, are small, efficient, robust, and potentially low cost, making them ideally suited for field use.

Recent developments in microchip solid-state lasers are introduced. A diode laser is used as an excitation source to pump a solid-state “chip” of approximately a few mm3 in size to convert the poor spatial and spectral mode output of the diode laser into a spectrally and spatially pure, low-noise beam. In addition, remarkable progress on pulsed operation, including Q-switching or mode-locking, and nonlinear wavelength conversion through the use of microchip laser is described. The feasibility of each compact optical device is briefly discussed.

A quasi-phasematched second harmonic generation device with a periodically poled crystal is one of the most attractive methods for realizing high-quality visible lasers. We have recently newly developed a blue and green laser diode-pumped intracavity frequency doubling solid-state lasers through the use of periodically poled bulk MgO-LiNbO3. The periodically poled MgO-LiNbO3 with uniform periodicity was successfully obtained by a novel corona discharge method. The larger temperature-acceptance bandwidth of the periodically poled bulk MgO-LiNbO3 made it possible to realize the simultaneous temperature control of the laser diode and of the solid-state laser cavity. In addition, the stable single axial mode operation in the solid-state laser was accomplished by using an etalon. As a result, our new blue and green solid-state laser is compact, has high-stability laser power, low noise operation, and high beam quality. By using these blue and green solid-state lasers, a new digital photo-printing system and a new fluorescent image analyzer were realized.

We demonstrate control and synchronization of chaos in a Nd: YVO4 microchip laser. Stabilization of chaotic oscillations to high periodic orbits is experimentally and numerically accomplished by internal frequency resonance between the pump and loss modulation frequencies. Various periodic patterns can be extracted predictably from one chaotic oscillation by varing the pump modulation parameters. Characteristics of synchronization of chaos in two separate Nd: YVO4 microchip lasers are also analyzed in the case of employing two master-slave types and a mutually-coupled type. A secure optical communication system using chaos synchronization is numerically demonstrated.

The generation of narrow-band millimeter-wave radiation has been achieved by photomixing two longitudinal modes in a two-mode microchip laser. The two modes were frequency-converted to their second harmonics using an external cavity, then focused onto the photoconductive gap of an LTG-GaAs photomixer . A millimeter wave was generated from the photoconductive antenna and examined using a spectrum analyzer with a millimeter-wave mixer. The linewidth observed for the millimeter wave was 430 Hz at 101 GHz, which is only 1/230 the width of the individual laser modes. This narrow linewidth of the millimeter wave can be attributed to the cancellation of most of the frequency fluctuations embedded in the two modes due to their sharing the same volume in the same cavity.

Laser alignment thermal sensitive paper can be used for laser applications such as spot size measurements, beam characteristics, and determining beam mode. Thermal sensitive paper interactions with a 1.54 micron, 35 ns, 3.75 J, Er-Glass laser produced spots that had three concentric zones of response. These spots interact with each other if a minimum distance between exposures is not maintained. The distance needed between spots is directly related to the energy density incident upon the paper. Although there was no lot designation for the box of thermal sensitive papers used in this research, we were able to determine that the response of different papers in the same box could vary under constant laser exposure parameters. Therefore, investigators need to be cautious when extrapolating experimental data from exposures using this type of laser alignment paper.

High-power InGaN single-quantum-well (SQW) structure blue/green light-emitting diodes (LEDs) with an output power of 3-5mW were fabricated. The continuous-wave operation of bluish-purple InGaN multi-quantum-well (MQW)-structure laser diodes (LDs) was achieved at room temperature with a lifetime of 35 hours. The threshold current and the voltage of the LD were 80mA and 5.5V, respectively. By changing the indium composition of the InGaN well layers of the InGaN MQW LDs, the emission wavelength of the LDs was varied between 390nm and 440nm which was suitable for the application of a laser plant factory. Photocurrent spectra of the InGaN SQW LEDs were measured at room temperature. The energy differences between the absorption and the emission energy of the blue/green InGaN SQW LEDs were 290 and 570meV. Both spontaneous and stimulated emission originated from these deep localized energy states.

Self-sustained-pulsing A1GaInP laser diodes having very low intensity noise characteristics were successfully demonstrated by adopting a novel structure, which has highly doped saturable absorbing layer. Short carrier lifetime, which is indispensable for self-sustained pulsation, was realized by applying highly doped saturable absorbing layer. Self-pulsing laser diodes with the lasing wavelength of 650nm-band were fabricated, resulting in the threshold current of 76mA at 20°C. The relative intensity noise (RIN) was below - 138dB/Hz in the temperature range 20-60°C at the average output power of 5mW.

We have developed high-power and high-efficiency AlGaInP laser diodes with the power of 250mW and 700mW for a plant production light source. Their wavelength is 680nm that is efficient for the photosynthesis. By planting a lettuce seedling under the laser diode irradiation (250mW), the possibility of growing plant under the laser was confirmed. However, the leaves of the lettuce grown under the red laser diode were long and thin, and also their weights were light compared to the lettuce grown under high-pressure sodium lamp or metal halide lamp. Similar tendency was found on the lettuce grown at a higher light power. By adding a blue light, for example a blue fluorescent light or a blue LED, the shape of the leaves was much improved.

A high-power laser diode (>30mW) emitting at around 650nm is indispensable for a DVD-RAM system. Moreover, high-temperature operation (>-60°C) and high reliability are strongly required. In order to satisfy these requirements, optimization of active layer structure and development of a mirror hardening technology such as a window-mirror are introduced. In addition, some excellent laser performances that it suffers no optical damage up to 150mW and exhibits reliable 30-50mW operation at high-temperatures are presented.

Real refractive index guided self-aligned (RISA) AlGaAs laser diodes have various advantages over conventional complex refractive index guided lasers, which include low operating current, stablefundamental transverse-mode operation up to high power levels, good controllability of current and optica distributions, and so on. In this review, the concept of RISA lasers and their applications to optical data storage systems are presented. Taking advantage of low operating current characteristics of the RISA lasers, a number of optical elements which compose a conventional optical pickup are successfully integrated into a very small plastic package, which results in substantial reduction of pickup size in various optical disk systems.

Common experience indicates the quality of a printed image depends on the choice of the paper used in the printing process. In the current report, we have used a recently developed device called a micro-goniophotometer to examine toner on a variety of substrates fused to varying degrees. The results indicate that the relationship between the printed color gamut and the topography of the substrate paper is a simple one for a color electrophotographic process. If the toner is fused completely to an equilibrium state with the substrate paper, then the toner conforms to the overall topographic features of the substrate. For rougher papers, the steeper topographic features are smoothed out by the toner. The maximum achievable color gamut is limited by the topographic smoothness of the resulting fused surface. Of course, achieving a fully fused surface at a competitive printing rate with a minimum of power consumption is not always feasible. However, the only significant factor found to limit the maximum state of fusing and the ultimate achievable color gamut is the smoothness of the paper.

Drawings were made on various types of paper using lead pencils of grades from 4H through 10B. Raman spectroscopy verified both G and D peaks on all the drawings on PC print paper, PC photopaper, kent paper, and paper for silver halide print. After irradiation with a scanning femtosecond laser, silver halide paper drawn on with a 10B lead pencil maintained its surface flatness compared with the other types of paper. Raman spectroscopy on silver print paper showed a high-intensity G peak and a low-intensity D peak. After irradiating the scanning femtosecond laser on silver halide paper drawn on with a 10B lead pencil, Raman spectroscopy showed a high-intensity G peak and less intense of D peak together with a 2D peak around 2,700 cm−1 corresponding to the existence of multigraphene.

Significant research and development in the areas of microwave photonics in Brazil are presented in this paper. These include direct microwave modulation of semiconductor laser diodes, optical control of MESFETs and HEMT's as well as high speed fiber optic components. Future directions for research in this area are discussed. © 1993 John Wiley & sons, Inc.

It is shown that the main equations of a deformation instability model, the solutions of these equations, and the results given in the paper of F Kh Mirzoev are contained in earlier published papers of other authors. Comment on F Kh Mirzoev 1996 Quantum Electron. 26 806.

Mass ablation rate increases with laser power density following a power law dependence and a significant change occurs at 0.3 GW/cm $^2$ . A reflected laser temporal profile was measured from a brass sample. When the power density is greater than 0.3 GW/cm $^2$ +, the temporal profile changes. The transmitted laser-pulse temporal profile through a glass sample also was measured. When the power density is greater than 0.3 GW/cm $^2$ , the later part of laser pulse becomes truncated. The power density at which the laser temporal profile changes for each case is same as the power density that the mass ablation rate coefficient changes. The ablated mass can absorb incoming laser radiation through inverse Bremsstrahlung. The mass becomes thermally ionized and opaque to the incident radiation, preventing laser light from reaching the surface. A model based on thermal evaporation and inverse Bremsstrahlung absorption was developed. Calculations show that plasma shielding occurs at approximately 0.3 GW/cm $^2$ . The experiments and model suggest that the significant change observed in mass ablation rate coefficient is caused by plasma shielding.

Laser atomic layer epitaxy technique is reviewed, and growth characteristics and surface processes in laser Atomic Layer Epitaxy (ALE) are described. The self-limiting mechanism is the key to attain the ideal layer-by-layer controllability in growth rate. The self-limited growth is obtained in a wide range of several growth parameters. The self-limiting mechanism is induced by the site-selective decomposition of alkylgallium precursors (alkylgallium precursors decompose only at the As surface, but not at the Ga surface), and the direct absorption of laser light in the chemisorbed alkylgallium layer provides the site selectivity.

Copper-phthalocyanine (CuPc) thin films were successfully fabricated via pulsed laser ablation. In order to maintain a molecule architechture in the deposited films, laser fluence must be kept near the laser ablation threshold. Despite of poor crystallinity exhibited in the films, the CuPc film still maintains its electrical property and works as a hole-transport layer in a double-layer electroluminescence cell emitting -500nm light. The crystallinity of CuPc thin films was improved by heating a substrate at -320K during the deposition or by irradiating the film surface with He-Ne laser at room temperature.

We have studied dynamical mechanism of laser ablation using combined time- and spatially-resolved measurements of laser plasma soft x-ray absorption spectroscopy and visible light emission imaging/spectroscopy. The obtained results indicate that there are no significant formation of silicon clustres and no growth of silicon nanoclusters till 2.55 ms after laser ablation. We have fabricated nanocluster-based silicon films by laser ablation in ambient gases and investigated photoluminescence at room temperature from the films. It is found that the growth of silicon nanocluster-based films with visible light emission can be well controlled by means of novel laser ablation methods.

The propagation of broadband ultrasonic pulses in combined media that consist of printing paper of different porosity saturated with different liquids is studied. The experiments are performed with three types of paper, namely, Zoom Ultra (Stora Enso, Finland) with surface densities of 80 and 100 g/m2 and Data Copy (Mo Do, Sweden) with a surface density of 160 g/cm2, and with two types of saturating liquids: ethanol and transformer oil. To excite ultrasonic pulses and to detect them with a high time resolution, the laser optoacoustic spectroscopy method is used. For each type of liquid-saturated paper, the phase velocity of ultrasound is measured in the frequency range of 5–35 MHz. The absence of any noticeable frequency dispersion of the phase velocity is revealed. The possibility of measuring the porosity of printing paper on the basis of the theoretical model of a two-phase medium with the use of the corresponding experimental data is demonstrated.

In 1990’s laser technology increased its volume in papermaking industry. Advantages of laser technology in these branches are flexibility, high speed, contact-free processing and possibilities of multifunctional applications. Anyhow, use of laser technology in papermaking has a minor role, mainly because of shortage of basic research results.Previous laser cutting trials performed within a national project in Finland had shown that uncoated paper and board can be laser cut with high speeds and good cutting edge quality (bright kerf, no carbonisation). The materials used in this study were talc, calcium carbonate and clay coated commercial LWC (light weight coated), CWF (coated wood free) paper grades and SC (supercalandered) papers. Also uncoated LWC paper was included. The cutting experiments contained tests of effect of different laser parameters like power, focal point position and focal length on the cutting speed and the cut edge quality.Tested papers all were suitable for laser cutting. Behaviour of cutting speed in relation to laser power was linear. Increase of mineral pigment coating increased laser power needed to cut mineral coated papers.Some of these cutting tests of coated papers showed also nonlinear behaviour. This occurred when CWF papers were cut with laser beam and laser power values were above 1100 W and a short focal length (63.5 mm) were used. Also cutting kerf widths were broadened. This behaviour was related to blue flame which occurs during cutting. This blue flame was concluded to consist of ionized CaCO3 pigment particles, which formed a cloud that blocked the laser beam entrance to workpiece. However, tested CWF-papers can be cut successfully with focal lengths 127 mm and 190.5 mm. With 127 mm focal length optics CWF papers could be even laser cut faster than with 63.5 mm focal length optics.In 1990’s laser technology increased its volume in papermaking industry. Advantages of laser technology in these branches are flexibility, high speed, contact-free processing and possibilities of multifunctional applications. Anyhow, use of laser technology in papermaking has a minor role, mainly because of shortage of basic research results.Previous laser cutting trials performed within a national project in Finland had shown that uncoated paper and board can be laser cut with high speeds and good cutting edge quality (bright kerf, no carbonisation). The materials used in this study were talc, calcium carbonate and clay coated commercial LWC (light weight coated), CWF (coated wood free) paper grades and SC (supercalandered) papers. Also uncoated LWC paper was included. The cutting experiments contained tests of effect of different laser parameters like power, focal point position and focal length on the cutting speed and the cut edge quality.Tested papers all were suitable for laser cutting. Behaviour of...

The effect of laser radiation on a German geographic map printed in 1846 is investigated. The sample is irradiated with pulsed and continuous wave radiation (cw) at a wavelength of 532 nm and fluences of 5 and 3 kJ/cm 2, respectively. A visible decrease in discoloration resulting from the pulsed irradiation is demonstrated. ATR FTIR and fluorescence spectroscopy are used for diagnostics. The discolouration of the laser irradiated map after five years and the corresponding spectral changes are discussed.

Laser consolidation (LC) is a novel computer-aided manufacturing process developed by the Industrial Materials Institute of National Research Council of Canada (NRC-IMI). This rapid manufacturing process produces net-shape functional metallic parts layer-by-layer directly from a computer aided design (CAD) model by using a laser beam to melt the injected powder and re-solidifying it on the substrate or previous layer. As an alternative to the conventional machining process,this novel manufacturing process builds net-shape functional parts or features on an existing part by adding instead of removing material. In this review paper,LC of CPM-9V tool steel,Ni-based IN-625 and IN-718 superalloys,and Ti-6Al-4V alloy will be discussed. The microstructures and functional properties of these laser consolidated materials will be examined along with several potential industrial applications.

The size distribution and total amount of the particles in paper pulp is vital information for the paper manufacturer in optimising process control and maintaining a high product quality. There is a further need for improving the on-line measurement methods to measure these parameters. It is known that fibre and fines fractions in the pulp have different optical and acoustic properties. In this study, we simultaneously use laser radar and laser generation of acoustic waves to further study optical and acoustic parameters, such as optical time delay, acoustic speed and attenuation. A near infrared pulse laser is used to illuminate the pulp suspensions and the time-of-flight of scattering photons is recorded; and at the same time, a high energy pulsed laser is applied to produce an acoustic wave. The acoustic wave propagates through the pulp suspensions and an acoustic transducer is used to detect the signals from which the attenuation and acoustic speed are determined. The results show that these combined optical techniques can potentially determine the content of fibres and fine particles simultaneously.