Energy deposition and heating during laser processing of materials are a consequence of the balance between the deposited energy, governed by optical parameters of the surface and characteristics of the laser radiation, and the heat diffusion, determined by thermophysical parameters and the interaction time. The kinetics of laser-induced plasma with maximum values of absorptance is described giving indication that maximum efficiency and optimum quality only can be achieved in a narrow range of intensity. The optical feedback resulting stochastically in temporal and spatial changes of intensity distribution controls surface finish and reproducibility that diagnostics and monitoring of laser intensity and mode structure during processing are essential requirements for optimum processing results. The heat flow governs the load and the losses of the heat affected zone with the different analytic and numerical models for the mathematical analysis of the multiparameter problem laser materials processing providing a testing comparison with the physical picture and an easy estimation of process parameters in applications.

Mechanism of laser beam absorption was analyzed in key hole welding of thin plate and deep penetration welding of thick plate on the basis of the two-dimensional cavity model where beam is absorbed by cavity wall and ionized metal vapor. The beam absorptivity of the cavity wall A and the absorption coefficient of the plasma u are approximately 50 % and 1- 1.5 cm^-1, respectively. In key hole welding of thin plate, laser beam is absorbed predominantly by the liquid cavity wall and the cavity shape is self-controlled so as to absorb the energy required for bead formation. In deep penetration welding of thick plate, laser power is absorbed mainly by plasma where the self-controlling is less effective, and hence excess energy absorbed at low welding speeds is w'sted to widen the bead with little increase in penetration depth. In vacuum of 10^-3-10^-4 torr, u decreases down to approximately 0.5 cm^-1, providing large penetration depth.

Heating effects in laser processing of metals are greatly influenced by the metal reflectivity, R and by the coupling coefficient ε = 1 - R. In this paper we discuss several methods by which ε may be measured, including a simple calorimetric technique that yields ε(T) for highly reflecting metals. This technique has been applied to measure E(T) for a variety of metals for CO₂ and excimer laser radiation.

Steel and cast iron surfaces that are to be laser transformation hardened must first be coated with an absorptive layer to enhance coupling of the CO₂ laser beam with the workpiece. A series of laser surface heating experiments was performed on plain carbon steel plates which had been coated with an absorptive copper selenide layer. A 1.5 kw cw CO₂ laser was used to scan the steel surfaces with a Gaussian beam of constant power and spot size. An analytic solution to the heat transfer equation was used to calculate the hardened depths for comparison with measured values. A comparison of calculated and measured hardened depths yielded values of the effective coupling coefficient as a function of the beam interaction time. The effective coupling coefficient decreases from ≈1 at the shortest interaction times to ≈0.6 at the longest. Reduction of the effective coupling coef-ficient is associated with destruction of the copper selenide layer.

The beam characteristics from two 2kW CO₂ lasers coupled as an oscillator/amplifier pair is discussed with particular reference to the power gain and mode structure variations generated in the amplifier section. It was found that gain saturation, plasma saturation and beam clipping phenomenon were the dominant effects governing power amplification. The mode structure was essentially unaltered by the presence of a plasma in the amplifying section. Some alteration in the mode was noticed for high input powers from the oscillator due to clipping.

The industrial future of lasers in material processing lies in the combination of the laser with automatic machinery. One possible form of such a combination is an intelligent workstation which monitors the process as it occurs and adjusts itself accordingly, either by self teaching or by comparison to a process data bank or algorithm. In order to achieve this attractive goal in-process signals are required. Two devices are described in this paper. One is the Laser Beam Analyser which is now maturing into a second generation with computerised output. The other is the Acoustic Mirror, a totally novel analytic technique, not yet fully understood, but which nevertheless can act as a very effective process monitor.

Experience with lasers in manufacturing industry over the last twenty years has highlighted the flexibility of the equipment by the diversity of its applications. As a result, the use of the CO₂ laser for cutting, welding and heat treatment is now commonplace on the factory floor. Falling into line with current manufacturing philosophy, the laser has been seen to be used increasingly in multipurpose, multi-axis type applications. The design and development of these Flexible Laser Manufacturing Systems has exploited the particular features of the CO₂ laser light. This paper will generally consider the various beam and work handling techniques available to the laser systems designer. Consideration will also be given to the mechanical, optical and system control parameters. A number of examples of Flexible Laser manufacturing systems will be reviewed. Particular reference will be made to the development of a laser beam guide suitable for use with a conventional industrial robot.

Most laser cutting systems utilise a gas jet to remove molten or vaporised material from the kerf. The speed, economy and quality of the cut can be strongly dependent on the aerodynamic conditions created by the nozzle, workpiece proximity and kerf shape. Adverse conditions can be established that may lead to an unwelcome lack of reproducibility of cut quality. Relatively low gas nozzle pressures can result in supersonic flow in the jet with its associated shock fronts. When the nozzle is placed at conventional distances (1-2mm) above the workpiece, the force exerted by the gas on the workpiece and the cut products (the cutting pressure) can be significantly less than the nozzle pressure. Higher cutting pressures can be achieved by increasing the height of the nozzle above the workpiece, to a more damage resistant zone, provided that the shock structure of the jet is taken into account. Conventional conical nozzles with circular exits can be operated with conditions that will result in cutting pressures up to 3 Bar (g) in the more distant zone. At higher pressures in circular tipped nozzles the cutting pressure in this zone decays to inadequate levels. Investigations of a large number of non-circular nozzle tip shapes have resulted in the selection of a few specific shapes that can provide cutting pressures in excess of 6 Bar(g) at distances of 4 to 7mm from the nozzle tip. Since there is a strong correlation between cutting pressure and the speed and quality of laser cutting, the paper describes the aerodynamic requirements for achieving the above effects and reports the cutting results arising from the different nozzle designs and conditions. The results of the work of other investigators, who report anomalous laser cutting results, will be examined and reviewed in the light of the above work.

In the present paper the electric field and currents in the air-breakdown plasma, produced by the train of nanosecond pulses of TEA-002 - regenerative amplifier near the un-charged targets are studied. The breakdown thresholds and the efficiency of plasma-target heat transmission are also measured. The results of numerical calculations made for increasing of the pulse train contrast with respect to the background in a regenerative amplifier are advanced.

Simultaneous measurements of the transient conductance, to determine the molten layer thickness versus time, and the time-dependent surface reflectance, to determine the melt duration at the surface during pulsed laser irradiation, are reviewed. These real-time measurements have been applied in a variety of studies of Si and Si-based alloys. In crystalline Si, melt initiates at the surface and propagates to some depth, whereupon the motion of the liquid/solid interface reverses and the material solidifies. In amorphous Si, these measurements were used to determine the melting temperature of the amorphous phase and the mechanism by which explosive crystallization occurs. In Si implanted with impurities, combined transient conductance and reflectance measurements reveal the occurrence of such novel melt and solidification scenarios as internal nucleation of melt and surface nucleation of solid on molten Si. Internal melts, which were previously unexpected, appear to be quite common and explain unusual microstructures observed by TEM.

We review recent advances in studies of solid phase crystallization of amorphous silicon at high temperatures. The kinetics of solid phase epitaxy and random crystallization have been investigated over the temperature range from 550°C to -1350°C using cw Ar laser and flashlamp-pumped dye laser heating and time-resolved reflectivity measurements of crystallization rate. We examine the interplay between solid phase epitaxy and random crystallization in lightly doped films, and the temperature and concentration dependent competi-tion between crystallization, precipitation and phase separation in amorphous layers containing In and As at concentrations greater than 0.5 at.%.

Pulsed or scanned energy beams have been shown to be very useful for many semiconductor applications, ranging from annealing of ion-implanted damage to preparation of materials.

The surface morphology of CdTe, Cd and InSb targets following vacuum pulsed laser evaporation has been examined. Vaporization of CdTe does not change the stoichiometric conditions of the surface, but precipitation of In is observed in the case of InSb. A stable vaporization rate can be obtained with a scanning laser beam after an initial layer of material is removed from the target and a characteristic surface structure is formed.

Epitaxial regrowth of ion implanted silicon and formation of metal silicides through the reaction of Si single crystals with thin deposited metal (Pt, Pd, Cr, Mo, Ti) films was obtained with different (ruby, Nd:glass, excimer) pulsed laser sources. Temperature profiles and evolutions into the samples were calculated. It was found that partial and even complete reactions of the metal films with silicon can be obtained at laser fluences lower than those needed for melting of the materials. The morphology of the irradiated surfaces was studied with a scanning electron microscope. Formation of damage ripple patterns is discussed. Epit-axial regrowth and silicide formation without surface damage of the irradiated materials was obtained by using excimer lasers.

A brief outline of several approaches taken to model the thermal behavior of laser materials interaction is presented. Starting with simple one-dimensional analytic solutions for heat conduction in opaque solids; it then transcends through numerical simulation in two dimensions by finite difference techniques; and finally discusses more complex finite element analysis. This rationale is based upon findings that gentler forms of heat treatment by an extended laser source may be modeled quite accurately by one-dimensional analytic expressions in closed form, while harsher situations such as those encountered in laser welding by a concentrated source generally require the use of numerical simulation methods. Illustrative examples are used to highlight thermal modeling approaches, graduating from simpler to more complex laser material interaction situations.

A fully automated laser process has been installed on a main stream production line for the manufacturing of electrical steel. The process uses high power continuous wave Nd:YAG lasers to refine the magnetic domain structure in a high magnetic permeability sheet steel product. The result is a typical 10% reduction in the electrical energy lost when the steel is used in a transformer core. A mathematical model of the process with dynamic sensor input is used by a computer to control the laser power and scan rate to ensure magnetic quality improvement independent of processing speed.

A wear-resistant Cr-Mn-C clad was produced on an AISI 1016 substrate by a laser technique using a defocused beam and a powder delivery system. The resulting physical properties were measured and correlated to processing parameters. The tribology and micro-structure of the clads were evaluated and compared to hardened 440-C stainless steel, Stellite 6, and AISI 1016. The laser processed clads were more wear-resistant than the materials they were compared to. The alloy distribution varied within the clads. The variation agreed with predictions of theoretical models of laser molten regions.

Observations are reported on the microstructure, defects and diffusion in AISI 1018 steel, surface alloyed with chromium by 2KW continuous wave CO₂ laser. The nature of alloying and chemical diffusion profile as a function of intertrack separation distance affects the final content of alloying element in surface layer. The ratio of number of laser tracks to width can be optimized to get minimum of cracking, maximum hardness and most uniform alloying of species.

The role of the plasma during laser materials interaction is studied using emission spectroscopy. The experiments were carried out in two stages: firstly, with a pure argon plasma and secondly with an aluminum target. The electron temperature distribution and electron density were determined. The experimental results were used to estimate laser attenuation and refraction as the beam propagates through the plasma column. Thus, transmitted energy and energy distribution on the surface were determined. This is expected to be a more realistic input for transport phenomena models based on absorbed energy.

Metallographical (optical, TEM, SEM), spectroscopic, abrasive wear resistance and microhardness investiga-tions of Fe/Cr/Mn/C steels heat-treated by a continuous CO₂ laser are described. Laser hardening resulted in wear resistance of 1.4 - 1.6 times better than that of conventionally hardened steels. Laser melting followed by rapid solidification allows formation of a solidified layer with high wear resistance only when the scanning velocity and mass of the samples were sufficient to realize high cooling rates. The variations in the wear resistance and microhardness with distance from the heated surface were similar. The grain refinement caused by rapid laser-heating and high stresses induced during cooling create essentially fine, highly dislocated lath and internally twinned martensites with some amount of stable, interlath retained austenite. This structure has in turn beneficial effects on wear resistance, and toughness. Laser-heat treatment for deep melting of the surface layers of the steels shows only a small improvement in wear resistance. Such heat-treatment results in delta ferrite retention (10Cr steel) and chromium segregation to cell-boundaries.

This paper reviews CO₂ laser processing of glass and single crystal fibers. For such applications it is necessary to restructure the laser beam and uniformly distribute it around a rod. A reflaxicon system using a concave conical axicon as the first reflector has been described. An interesting feature of this scheme is that the radiation intensity profile is similar to the shape of the neck down region observed in fiber drawing and the single crystal growth process. This provides a more uniform temperature distribution in the laser irradiated region. Analysis of a simple model and experimental results show that the short heat zone length and the corresponding radial temperature gradients limit the preform size and fiber drawing speed. However these very features are beneficial in fabricating fiber based components, drawing of fibers from glasses prone to devitrification, and the growth of single crystal fibers.

We propose an original approach to describe the transient behaviour of experimental optical coupling parameters of materials, i.e. absorptivity, reflectivity, ... at frequency w, versus time t. This analysis, based on the distribution theory and Laplace transforma-tion, extends and generalizes the classical definition of stationnary parameters, including temporal variations of surface temperature. It provides a method to deduce characteristic coefficients of laser-material interaction from experimental data on reflected and transmitted laser beams. At last, this method presents advantage of using simple rules of operational calculus as developped for electronic applications.

In this paper, we report the manufacture of the ring color tape for teleprinter cut by laser beam, including the priciple, the processing, the experimental device, results and the discussion about the optimum operation condition etc.

The total value of all lasers sold during 1986 in the non-Communist world will exceed US $600 million. This paper examines these sales and categorizes them according to application and according to type of laser. The results are presented both in terms of numbers of lasers sold, and in terms of the value of those lasers. The data are based on extensive interviews with laser manufacturers and laser users.

The development of the CO₂ gas laser in the mid-sixties, has paved the way for the potential use of lasers in the fabrication of various driveline and body parts for automobiles. Much laser and laser metalworking research has been conducted in the United Kingdom and Europe (early research on cutting dates back to 1967). However, the automobile industries in both communities have been cautious in using lasers in production for heat treatment and welding. This paper outlines, in respect to the automobile industry, developments in laser equipments, current production applications, potential application studies and particular problem areas which are being researched. The application areas discussed cover: laser cutting, heat treatment and welding.

The decision in favour of active research into laser technology was taken in our company in 1978. In the following years we started with the setting-up of a laser laboratory charged with the task of performing basic manufacturing technology experiments in order to examine the ap-plications of laser technology for cutting, welding, hardening, remelting and secondary alloys. The first laboratory-laser - a 2,5 kW fast axial flow CO2 laser - is connected with a CNC-controlled workpiece manipulation unit, which is designed in such a way that workpieces from the smallest component of a car gearbox up to crankcases for commercial vehicles can be manipulated at speeds considered theoretically feasible for laser machining. The use of the laser beam for cutting, hardening and welding tasks has been under investigation in our company, in this laboratory for some 6 years. Laser cutting is now no longer a question of development, but is instead standard practice and is already used in various sec-tions of our production division for pilot-series manufacturing and for small batches. Laser hardening has, in our opinion, great possibilities for tasks which, for distortion and accessibility reasons, cannot be satisfactorily performed using present-day processes, for instance induction hardening. However, a great deal of development work is still necessary before economically reasonable and quality-assured production installation can be undertaken. Laser-welding is now used in series-production in our company for two engine components. More details are given below.

Recently in Japan, laser processing is increasingly being employed for production, so that laser cutting, laser welding and other laser material processing have begun to be used in various industries. As a result, the number of lasers sold has been increasing year by year in Japan. In the Japanese automotive industry, a number applications have been introduced in laboratories and production lines. In this paper, several current instances of such laser applications will be introduced. In the case of welding, studies have been conducted on applying laser welding to automatic transmission components, in place of electron beam welding. Another example of application, the combination of lasers and robots to form highly flexible manufacturing systems, has been adopted for trimming steel panel and plastic components.

Demands for greater flexibility and accuracy in the manufacture of automobile trim parts has made single-ply laser cutting an attractive proposition. Lasers are able to cut a large variety of cloth types, from vinyls to velours. Unlike mechanically cut parts, which in the case of velours produce rough edges and dust problems, laster cutting of parts produces smooth edges, fumes and fine particulate. A detailed study of the nature of the laser effluent from a cross section of typical synthetic cloth found in an automotive trim plant was undertaken. Most samples were cut by a fast axial flow, 500 Watt, continuous wave CO₂ laser. A 254 mm (10-inch) focussing optics package was used. The width of the kerf varied with the material, and values were determined at between 0.2 and 0.7 mm. Particle size distribution analysis and rates of particulate emission for each cloth were determined. Gases were collected in gas sample bags and analyzed using Fourier transform infrared analysis. Low boiling point organics were collected on activated charcoal tubes, identified on a gas chromatograph mass spectrometer, and quantified on a gas chromatograph. Inorganic contaminants were collected on filter paper and analysed on an inductively coupled plasma atomic emission spectrometer. A number of different effluent control systems were evaluated. Due to the very fine and sticky nature of the particulate, filters capable of removing particulate sizes in the 10 μm or lower range, tend to clog rapidly. Laboratory scale models of wet scrubbers, and electrostatic precipitators were built and tested. The most effective dust and effluent gas control was given by a wet electrostatic precipitator. This system, in conjunction with a scrubber, should maintain emission levels within environmental standards.

This paper will outline the basic information that determines the approach that a prospective CO₂ laser cutting user will take to the purchase of a system. The ability of this type of machine to cut a wide range of materials will be reviewed along with speed and edge-quality parameters. A discussion of the choices available in the marketplace for each of the basic components in a laser maching system will be presented. Three commercially available laser machining systems will be described and compared and the widely different approach taken by each of the design engineering groups involved will be detailed. The effect of upcoming innovations in CAD-CAM and Robotics on the laser cutting systems of the future will also be discussed.

With the greater acceptance of laser technology as a viable alternative to traditional metals joining methods, the need has arisen to integrate lasers into efficient high production systems. This paper will describe one such system which is dedicated to the automated processing and laser welding of automotive transmission gear components. The system features two (2) 6 KW CO₂ lasers, automated part manipulation, vapor degreasers, air cylinder press stations, fully enclosed weld stations incorporating bottom delivery methods, and programmable computer control which allows complete monitoring throughout the entire production cycle. It is the intent of this paper to describe all segments of the system in detail as to design, manufacture, and integration. Concerning this specific application, an overview from initial inquiry through final installation of the manufactured system will be presented and will focus on the laser welding process and parameter development as it relates to the total systems concept and production goals.

Systems used in observing laser beam shape and output power are described in the following text with block diagram illustrations. This equipment is integrated into Combustion Engineering's product line of high power (up to 8.0 kW) A.C. excited industrial CO2 gas transport lasers. Also outlined are systems for opto-mechanically adjusting laser beam profile and in controlling laser beam output via a closed-loop feedback servo mechanism.

Until recently, applications of carbon dioxide (CO₂) lasers in industry have primarily used high-power laser systems for cutting and welding. Today, the most rapid growth rate is occuring in applications of small, sealed laser systems to soldering, wirestripping, marking, sealing, degating and slitting of a wide variety of materials. In the future, small CO₂ laser based systems will be in use in shopping centers and department stores, and unit sales will be in the multiple thousands per year.

While laser cutting of sheetmetal has attained wide acceptance in the automotive industry for the purposes of prototyping and very limited preproduction work, the production rates possible with currently available systems have precluded the use of this technique in a production environment. The device design to be described embodies a high speed X-Y positioner carrying a cutting head with limited Z-axis capability. This approach confers two main benefits, first, production rate is limited only by laser power, since the positioner technology selected will permit movement at rates up to 1.5 m/s (60 in/s), second, the use of a high speed non-contact surface follower to control the Z-axis movement reduces the need to clamp the workpiece rigidly to a precision reference surface. The realized reduction of the clamping requirement permits some latitude in the feed methods that can be employed, allowing the use of coil or sheet feeding as appropriate. The author will provide estimated production rates for the proposed design and demonstrate that a suitable choice of laser source and material feed will permit the production of parts at a rate and cost comparable to conventional blanking with the advantage of much greater flexibility and reduced retooling time.

The outstanding potential of radio-frequency discharges for the excitation of high power CO₂-lasers has been demonstrated for fast axial flow and transverse flow lasers. Outcoupled optical power densities up to 5 W/cm³ have been obtained with nearly diffraction limited beam quality. Good beam quality has been achieved for cw as well as for pulsed mode operation by applying a double pass unstable resonator in the transverse flow laser.

This paper introduces some of the important aspects of using lasers with robots for an automated environment. Salient features of a laser robotic cell are discussed. Potential error sources are illustrated. The goal of this paper is to provide a background for understanding the makeup of today's laser robotics systems.

A five axis robotic laser welding system has been designed and built for an "on-line" automotive joining application. A high power CO2 laser beam is manipulated through the use of a robotic beam delivery system and is focused onto the work piece. An optical probe communicates the coordinates or geometry of the parts to the clamping and welding robots. The essential features of the robots, laser, optical probes and clamping system have been discussed. The system versatilities also have been outlined.

Although lasers have, for some time now, been used for performing a wide range of industrial material processing tasks, most of these applications have involved simply moving a workpiece under a fixed laser beam - in order to accomplish the specific processing action desired. This method of doing laser material processing, although highly effective, produces certain limitations on the overall shape of the workpiece that can be processed. As such, a number of manufacturers of laser material processing systems now supply units which instead fix the workpiece - and provide the necessary processing motion by moving the laser beam itself. In the following, systems having different degrees of laser beam manipulation capability are fully described - and the enhanced flexibility this method of laser processing provides users is then discussed in detail.

The RL5, a five-axis robot, is designed to steer a powerful laser beam on 3 dimensional (3D) trajectories with a great accuracy. Cutting and welding with a CO₂ laser beam, drilling with a YAG laser beam are some applications of this machine which can be integrated in a production line. Easy management and modifications of trajectories, obtained either in a teaching mode or by a CAD-CAM system, give the laser tool its main interest : flexibility.

A flexible laser robot system is described which has been selected for the purpose of cutting additional openings in entire bodies in white on the conveyor. The lightweight CO₂ 400-W-laser generator is carried and moved computer-controlled by the VOLKSWAGEN robotic system with a fixed 3-mirror robot arm for minimizing losses of energy and for increasing quality and reliability. In a pilot project this technique is integrated in the production line at a final stage of production and can be started with the designation of the vehicle's body.

A composite is a mixture of two or more materials which are mutually insoluble and as a whole make up a new and improved material. Composites are becoming the desired materials of the future as many new organic and inorganic materials are improved. But in order to keep up with this advancing technology, machining methods must also advance in parallel.

The use of laser systems in the production environment is becoming increasingly important as a more sophisticated technology is needed to solve manufacturer's needs. While users are becoming more knowledgeable about this type of equipment, it remains a major goal for the system builder to develop reliable systems based on sound process definition, design and integration, and support.

Raycon Corporation is a builder of quality machine tools. Combining this with applications expertise to produce high technology production machinery systems using EDM, lasers and other processing methods to solve our customers' production problems is our product. The company has several standard laser machine systems which can be constructed from standard building blocks. The number of axes and travel, the controller requirements, and the required laser type, size and manufacturer are discussed with our customers, and the system to meet their needs is decided upon. These requirements are then built into a processing system for manufacturing use. Several of these systems which are in the field are described, and their purposes and how they accomplish their task are explained. Also, types of YAG and C0₂ lasers available are described and their optimum use explained. Some specific examples of type versus applications are: YAG low-divergence lasers for trepanning heat-resistant alloys for jet engine turbines; YAG oscillator-amplifier lasers for percussion drilling of cooling holes in jet engine turbine blades; and several special laser machine systems for processing automotive parts are discussed. A few words on laser safety are included to allay some common fears concerning the use of laser technology in the factory environment.

High-speed laser welding systems have been developed to hermetically seal electronic packages, diaphragms, etc., for commercial, medical, and military applications. An inert atmosphere chamber is incorporated when welding must be done in a moisture-free and oxygen-free gas environment. Interface of a multi-axis positioner and computer numerical control with the laser allows programmability of all weld schedule parameters. This degree of automation minimizes process deviation, decreases the risk of human error, and accommodates dimensional tolerances and dissimilarities in part configuration.

Some preliminary results are presented concerning the damages and the evolutions of metallurgical properties of Fe-C alloys induced by laser shock waves at two different laser wavelengths. In the present work, changes induced by laser shocking have been measured : pressure, microhardness, residual stresses. In addition microstructural variations at the surface and in depth have been observed.

The design and development of an industrial CO₂ laser marking system is discussed with specific reference to the reliability and lifetime performance of the laser subassemblies. The design and development of the various laser subassemblies has continued over the last ten years, and lifetime and reliability data is available from many in-house life tests and also from an installed product base of over 1400 lasers.

The use of pulsed lasers for date stamping and batch coding of products has become an established technique. A common approach is to illuminate a specially prepared stencil mask with the laser pulse and image this onto the target material. To change the inscription the mask must be changed manually or electromechanically, which becomes unwieldy in applications requiring individual inscriptions such as serialisation or the recording of quality control data. This problem can be overcome by the use of a novel acousto-optic technique wherein a row of dot matrix alpha-numerics can be generated from a single laser pulse. By this means any alphanumeric mark can be produced on a shot by shot basis under computer control. A computer controlled marking system is described which utilises this technique together with a flashlamp pumped Nd:YAG laser, in which the single multiple acoustic column deflector, the anamorphic optical train and the laser cavity are all contained within a compact head assembly. The design of the multi-character cell, optical train, beam delivery system and electronics are discussed. A new multiple Q-switched version of the Nd:YAG system is also described enabling a wider range of harder materials to be marked. The technique is applicable also to CO₂ TEA laser systems, although a different cell design philisophy is required. Such a system has also been developed and this is briefly outlined. The performance of both systems against various target materials is reviewed.

The first discharge pumped excimer lasers introduced in the 1970's were derivatives of N₂ and C0₂ TEA lasers. They had spatially non-uniform outputs, relatively small output energies, low average powers, short operating lifetimes, and poor reliability. Today, more than a decade later, excimer lasers are just now maturing to the point where they are starting to enter the industrial workplace. This paper will review the transition from CO₂/N₂ to excimer technology, the engineering hurdles excimer lasers must overcome to make them viable industrial tools, and the current state of the "industrial excimer laser".

Excimer lasers are finding increasing use in both semiconductor and materials processing. In the semiconductor area, this has led to the development of excimer based processes for lithography, film deposition, etching, doping and annealing. In materials processing, the unique capabilities of the excimer laser offers the potential for greatly extending the range of laser based cutting, drilling and marking techniques. This paper is intended to provide an overview of these areas. Attention is given to the means by which the excimer laser addresses the critical needs in each particular case.

We have designed, constructed, and begun activation of a large scale laser facility for the Laser Isotope Separation Program at LLNL. The system integrates high-performance copper lasers and dye lasers, as well as optical and instrumentation and control systems to produce high-power, high-repetition rate, multi-wavelength tunable light. Performance characteristics as well as packaging and operating philosophies will be discussed.