Interferometric lithography (IL) techniques provide a demonstrated, low-cost, large area nanoscale patterning capability with feature resolution to approximately 50 nm. Combining IL with anisotropic etching and with 3D oxidation techniques provides a suite of techniques that accesses a broad range of Si nanostructures over large areas and wit good uniformity. Optical characterization includes measurements of reflectivity for a wide range of 1D grating profiles, and Raman scattering characterization of Si nanostructures. Three regimes are found for the Raman scattering: bulk, resonant enhanced and asymmetry and splitting.

Optics with resolution within the wavelength - scanning near-field optical microscopy - is highly important science field nowadays. Main parameters of the SNOM - resolution, contrast, energetic efficiency are defined by optical probes characteristics: aperture size or curvature radius of the sharp, geometry, material, etc. Fabrication and testing of optical probes in nanometric scale of size are described in the paper. For fabrication of near-field probes the laser many-steps drawing and chemical etching of single- and multimode optical fibers is realized. Investigation of far- field light distribution and theoretical reconstruction of near field carried out the testing of probes.

We review the bond breaking and structural changes on clean surfaces of Si(111)-(7X7) and of InP(110)-(1X1) induced by ns- and fs-laser irradiation with fluences below thresholds of melting and ablation. Atomic imaging of the irradiated surface by scanning tunneling microscopy (STM) has shown that the bond breaking of adatoms of Si(111)- (7X7) is induced by an electronic process to form adatom vacancies mostly at individual adatom sites. Si atoms in the electronic ground state are desorbed with a peak translational energy of 0.06 eV, as a direct consequence of the bond breaking. On the other hand, STM images of the irradiated InP(110)-(1X1) surfaces have revealed the preferential removal of the top-most P atoms, with significant formation yields of vacancy strings consisting of several adjacent vacancies on the quasi-one dimensional P rows. The isolated In vacancies are also formed, but with a much smaller yield. For both surfaces, bond breaking takes place at intrinsic sites of the surface structures, and the efficiency is strongly site-sensitive, resonantly wavelength-dependent, and highly super-linear with respect to the excitation intensity. The electronic bond breaking is shown originate from non-linear localization of excited species in surface electronic states.

We have compared the desorption of positive ions, including Mg⁺ and MgO⁺, form ionic magnesium oxide single crystals following pulsed laser excitation using either nanosecond or femtosecond sources. Following optical excitation, desorbed ions are rapidly extracted and mass analyzed using standard time-of-flight techniques. Ion yields and velocities are determined as a function of laser fluence. The threshold similarity is a surprising result, as sub-band gap nanosecond pulses are only likely to excite defect states efficiently, while the ultrahigh peak-power femtosecond pulses could in principle induce multiphoton and avalanche excitation. We argue that at least in this specific case, the important factor appears to be merely the number of photons and not the pulse duration. However, it is observed that femtosecond excitation yields considerable H⁺ and less interference from impurity alkali ions than does nanosecond excitation. The source of the protons is presumably the hydroxylated MgO surface.

This article presents an overveiw of recent mechanistic studies of laser-stimmulated desorption from rough metal surfaces and, as an application, describes novel experiments taht expoit thermal desorption to fabricate small silver particles with an extrmely narrow size distribution. Such systems are of great interst in catalysis or integrate doptics and many other fields.

We have succeeded for the first time to simulate phase transition from metal to vapor. This success is due to the CIP method that can treat solid, liquid and gas together and can trace a sharp interface with almost one grid. For these types of problems such as welding and cutting processes, we need to treat topology and phase changes of the structure simultaneously. Furthermore, the grid system aligned to the solid or liquid surface has no meaning and sometimes the mesh is distorted and even broken up. The CIP method developed by the authors does not need adaptive grid systems and therefore removes the problems of grid distortion caused by structural break up and topology change. In this paper, we will give a brief introduction of the CIP method, then report here the application to laser-induced evaporation and welding process. In the former case, aluminum is evaporated well after the laser beam needed and evaporation occurs with a large angle to the target normal leading to large debris. In the latter case, a deep penetration welding of SUS304 by TAG laser has been successfully replicated the experiments and the simulation clarifies the formation mechanism of keyhole.

Laser plasma interaction during pulsed laser ablation is investigated by ultrafast phototube detection. There are two peaks in an optical signal with the first peak attributed to laser scattering and the second one to plasma generation. As laser fluence increases, the second peak rises earlier to overlap with the first one. The signal is fitted by different distribution functions for the laser scattering and the plasma generation. Peak amplitude and its arrival time, full width at half maximum (FWHM), starting time and termination time of the distributions are studied for different laser fluences and detection angles. Laser pulse is mainly scattered from the plasma during the laser ablation. Peak amplitude of the laser scattering increases but its FWHM decreases with laser fluence. Angular distribution of the peak amplitude can be fitted with cosⁿ while detection angle has no obvious influence on the FWHM. In addition, FWHM and peak amplitude of the plasma increase starting and scattered laser pulse termination is proposed as a quantitative parameter to characterize laser plasma interaction. threshold fluence for the interaction can be estimated to be 3.5 J/cm² for KrF excimer ablation of silicon. For laser fluence above 12.6 J/cm², the plasma and scattered laser pulse distributions tend to saturate.

Ultrashort-pulse lasers are increasingly being used for laser-induced surface modification, texturing and marking of insulators. Ultrashort pulses interacting with insulators in the vibrational IR produce a number of novel effects of potential utility in materials processing and analysis applications, including the creation of microbumps, microdimples, generation of hydrodynamic instabilities, and creation of smooth ablation craters. This paper describes recent results in the study of ultrashort-pulse laser interactions with surfaces when the irradiation is in the 2- 10 micrometers range. The laser source was a tunable, free- electron laser with 1-ps micropulses spaced 350 ps apart in a macropulse lasting up to 4 microsecond(s) , with an average power of up to 3W. This unusual pulse structure makes possible novel test of the effects of resonant vibrational excitation, controlling the ratio of absorption depth to thermal diffusion length, and desorption and ionization by resonant excitation. The mechanisms underlying these effects, including vibrational excitation and relaxation dynamics, as well as their implications for materials-modification strategies, are discussed with reference to recent experimental examples.

Ultrashort laser pulses have considerable potential for micron and sub-micron structuring of several materials. The lower energy impact, the reduction of thermal damage, the elimination of laser-plume interaction, and the exploitation of nonlinear optical effects all contribute to a strong improvement when compared to results using pulse widths in the nanosecond range. Depending on the choice of fluence compared to the damage threshold, with ultra-short laser pulses one is able to generate different types of structures, minimizing the heat affected zone. The damage threshold drops dramatically during the first laser shots, due to defect incubation. This has important consequences for applications, such as laser machining and for the lifetime of optical components. At a fluence below surface damage threshold we were also able to generate bulk modifications of different size and location in a controllable fashion by variation of laser pulse width, energy and number of shots, utilizing the beam narrowing effects during self focusing. A study of the dependence of the structure depth on the square root of the laser power for a given pulse length provides a straightforward method for determining the non-linear index of refraction.

Practical high precise and efficient micromachining can be realized with computer controlled ultrashort laser pulses suppressing the thermal diffusion effect inside the material to be ablated. A direct translation from solid to the vapor state takes place at sufficient intensity levels. Experimental results of micromachining of different materials with femtosecond laser pulses at wavelengths of 800 nm and 267 nm from a commercial Ti:sapphire laser are presented. Holes down to a diameter below 1 micron have been drilled with 800 nm pulses into aluminum as an interesting metal with an absorption peak in the IR-range nearby 800 nm. Because of their low energy band gap semiconductors have a strong absorption at UV wavelengths. Arrays of holes down to 1 micrometer in diameter have been drilled into silicon and InP using 267 nm pulses. Results of fused silica as an example for transparent insulator materials are compared to result of semiconductors. The hole array manufacturing process takes only a few seconds. Precision can be improved by matching laser parameters to the processed material.

Recently there has been renewed interest in the grating alignment of liquid crystals because of its application in bistable nematic displays. In this paper, gratin and photoinduced liquid crystal alignment techniques based on excimer laser exposure of thin polyimide films are discussed. Gratings are etched into the alignment film using a KrF laser illuminated through a phase mask. These give homogeneous liquid crystal alignment with the liquid crystal directors aligned along the grooves of the grating. The observed azimuthal anchoring strength is compared with that predicted using Berreman theory. No pretilt is observed because of the grating symmetry. When a polarized excimer laser beam is incident on the film with a fluence below that required for ablation, an anisotropy is created photochemically by selective depletion of the polymer chains. Exposure of the polyimide with elliptically polarized light at non-normal incidence gives pretilted alignment. Grating etching followed by photoinduced alignment can be used to obtain pretilted grating alignment with a pretilt angle of 3 degrees.

We examined the feasibility of making various microscopic modifications in glasses by ultra-short pulses. It was confirmed that permanent refractive index changes, photo- reduction of samarium ions, the phenomenon of long-lasting phosphorescence, and creation of microcrystals with second- order nonlinear optical functions can be produced with a femtosecond pulse laser only in selective internal areas in glasses. By using a femtosecond laser with a high repetition rate, permanent optical waveguides can be successfully written in various glasses, where refractive index changes are continuously induced along a path traversed by focal point. We also confirmed that only rare earth ions of the core region in the waveguides are reduced by the laser irradiation.

This paper reports the development of high power excimer lasers with enhanced spatial and temporal coherence. These excimer lasers are applicable to writing fiber Bragg gratings by interferometric or phase-mask techniques. An excimer laser with a novel unstable resonator will be analyzed with respect to its suitability to the production of passive fiber optic components and in terms of production flexibility, efficiency, and reliability. A survey of applicability of this tool to short and long period fiber Bragg gratings will be presented.

Refractive index modification in optical multimode fibers was firstly demonstrated, as a fabrication method of double cladding structure, using plasma channeling excited by a high intensity femtosecond Ti:Sapphire laser. The induced refractive index modification in a pure silica multimode fiber with 100/110 micrometers core/cladding diameter was reached to the length of approximately 9-10 mm from the end of optical fiber with the diameters ranging form 5 to 8 micrometers at more than input intensity of 1.5 X 10¹² W/cm². It had graded refractive index profile that was a symmetric form from the center of a multimode fiber and the maximum values of refractive index change was 1.6 X 10^-2. According to the ESR spectroscopic measurement, it was observed that the concentration of defect of SiE center was heavily increased in refractive index modification refer to that of non-modification region. It was suggested that the defect was induced by the multiphoton absorption process through plasma channeling. Near-field pattern and beam intensity profile of a modified multimode fiber showed that bulk modification played a role as a double cladding structure. The fabrication method of double cladding structure in the end of multimode fiber can be useful tool for mode converter and single-mode connector in the fields of optical communication and optical sensor.

Low fluence UV laser stimulate desorption of ions form metal surfaces leads to the production of high kinetic energy species and also modifies the surface left behind. Both of these effects are small for an individual laser shot. The number density of the desorbed ions by the laser is very low - much less than a monolayer per pulse. The changes in the crystal surface are also subtle. However, in both cases there are cumulative effects after many laser shots which cannot be attributed to thermal or plasma pulse laser interaction processes. There is no evidence for thermal ions in the TOF mass spectrum. A laser ionization experiment was performed to measure the kinetic energy distribution of the desorbed neutral aluminum species. The high kinetic energy Al⁺ ions were used as monitor for insuring that the laser induced desorption process was always in the non- thermal regime during the surface modification experiments. We observe, via SEM, surface modification only after exposure to a large number of laser shots. Examination of the laser exposed surface with electron microscopy reveals quasiperiodic patterns made up of sub-micron scale ridges. After exposures to more than 100K laser shots, the quasiperiodic patterns break-up into irregular nodule-like shapes. Our data indicates the surface modification occurs without desorbing significant amounts of material.

Selective area CW Nd:YAG laser annealing of GaInAsP/InP quantum well (QW) structures has been investigated as a possible route towards the fabrication of monolithically integrated photonic circuits. Laser irradiation of a 5 QW laser structure, originally designed to yield lasers emitting at 1.5 micrometers , yielded material having a continuously changing band-gap ranging from 1.5 to 1.38 micrometers over the distance of about 3 mm. Bars with arrays of broad area lasers, having lengths from 300 to 600 micrometers , were fabricated form the processed materials. An individual bar comprised lasers operating typically between 1.4 and 1.5 micrometers . The lasers showed stable threshold current density and quantum efficiency as function of the operating wavelength. This demonstration indicates that the applied technology has the potential to realize the cost-effective fabrication of advanced photonic devices and photonic integrated circuits.

This work investigates the transient process of melting and microscale surface deformation upon pulsed Nd:YLF laser heating of Ni-P hard disk substrates. The laser pulse energy is in the range of 1.0 (mu) J to 5.0 (mu) J. The features produced by laser heating have a diameter of approximately 15 micrometers and height in the tens of nanometers range. A laser flash photography system is developed to visualize the transient topography development during the laser texturing process. The system has a nanosecond time resolution and sub-micron spatial resolution. A numerical analysis based on finite difference method is conducted to simulate the microscale energy transport and fluid glow. Comparison between the numerical and the experimental result helps to understand the physical mechanism of the process.

The laser combined express technique has been applied to high temperature measurements optical and thermal properties of different ceramics. It was found that the ambient atmosphere noticeably affects the physical properties of the heated ceramics that marks a noticeable structural and chemical modification of the material.

This paper explains current status and technological trends in laser materials processing applications in electronics and optoelectronics industry in Japan. Various laser equipment based on solid state lasers or gas lasers such as excimer lasers or CO₂ lasers has been developed and applied in manufacturing electronic and optoelectronic devices to meet the strong demands for advanced device manufacturing technologies for high-performance, lightweight, low power-consumption portable digital electronic appliances, cellular mobile phones, personal computers, etc. Representative applications of solid-state lasers are, opaque and clear defects repairing of photomasks for LSIs and LCDs, trimming of thick-film chip resistors and low resistance metal resistors, laser cutting and drilling of thin films for high-pin count semiconductor CSP packages, laser patterning of thin-film amorphous silicon solar cells, and laser welding of electronic components such as hard-disk head suspensions, optical modules, miniature relays and lithium ion batteries. Compact and highly efficient diode- pumped and Q-switched solid-state lasers in second or third harmonic operation mode are now being increasingly incorporated in various laser equipment for fine material processing. Representative applications of excimer lasers are, sub-quarter micron design-rule LSI lithography and low- temperature annealing of poly-silicon TFT LCD.

Photonics Research Ontario (PRO) is an Ontario Provincial Center of Excellence supporting a broad range of laser- processing activities within its photonics program. These activities are centered at the University of Toronto, and split between an industrial-user facility and the individual research programs of principal investors. The combined effort furnishes forefront laser system and advanced optical tools to explore novel processing applications in photonic, biomedical, and microelectronic areas. Facilities include laser micromachining stations, excimer-based mask-projection stations, extremely short wavelength lasers such as the molecular fluorine laser, and ultrafast laser systems. The latter two advanced laser offer interesting advantages and contrast in processing 'difficult' materials through linear and nonlinear absorption processes, respectively. These laser systems provide fine precision and strong interaction with a wide range of materials, including 'transparent' glasses, and also ceramics and metals. Applications fall broadly into several areas: wafer-level circuit trimming, high-resolution ultrasonic transducers, and the shaping of optical waveguides and Bragg-gratings for photonic components. This paper summarizes the laser-processing infrastructure and research activities at PRO.

Reports in 1982 of polymers ablated and etched by excimer laser radiation mark the founding of laser micromachining as a technology that in the intervening period has matured into a manufacturing process used by a diverse range of industries. This paper describes some of these industrial applications.

We are presenting a very successful new method of a laser welding technology developed in the Laser Institute of Mittel-sachsen. It allows us to join parts of alumina without any changes of their properties base don an additive free procedure. Furthermore it enables us to carry out the procedure without furnaces and in natural atmosphere within only a few minutes. In order to avoid thermally included stresses two laser beams are used. We will describe this procedure of laser welding of ceramics including the manner of preheating: their limits and advantages. The thermal influence on the welding bath and the grain structure will be discussed. High pure laser welded Al₂O₃-ceramic parts of various shapes will be presented. This new method of laser welding of ceramics opens up a wide field of new application. Almost now a lot of branches of industry have already shown their interest in this promising technique. Most applications are expected with sensor elements generally, and in the protection of electronic elements against high temperatures, abrasion and/or chemical attacks.

Laser cleaning was demonstrated both theoretically and experimentally to be an effective cleaning techniques for removing particulate and thin film contaminants from electronic materials. Two types of laser cleaning techniques have been discussed, relying on pulsed laser of the surface without or with the presence of a thin liquid coating. For dry and steam laser cleaning, cleaning models were established for removal of particles from substrate surfaces without or with a thin liquid layer by taking adhesion forces and cleaning force into account. The models not only explain the influence of laser fluence on cleaning efficiency, but also predict the cleaning thresholds. The laser-induced removal of organic thin film contaminants is considered due to laser ablation of the contaminants. Applications of laser cleaning to clean magnetic sliders, magnetic media surfaces, IC mold and PCB will also be addressed.

Chlorofluorocarbon-free laser cleaning techniques, compatible with cluster tool processing, have been developed for application to microelectronics processing, A KrF excimer laser is directed toward the wafer to be cleaned and rastered over the surface which might be intentionally covered by a thin liquid layer. It is demonstrated that various types of submicrometer-sized particles including polystyrene latex, silica and alumina, can be efficiently removed, by laser cleaning, from the front sides of silicon wafers. These results are explained by a particle adhesion model, including van der Waals forces and hydrogen bonding, and a particle removal model involving rapid thermal expansion of the substrate due to the thermoelastic effect and the pressure shock due to bubble generation in the condensed water film. The result of the calculations of the adhesions and removal models are consistent with the experimental observations. In addition, the excimer laser technique was successfully used to remove micrometer-sized metallic particles from the backsides of silicon wafers; such a removal represents a challenging task in today's integrated circuit technology.

The excimer laser annealing of amorphous silicon thin films has been investigated via optical diagnostics. Amorphous silicon films of 50 nm thickness are used in laser annealing. To obtain the transient temperature variation in the laser annealing process, the thermal emission and near- IR optical properties are measured. The front transmissivity and reflectivity are measured to obtain the emissivity at the 1.52 micrometers wavelength of the probe IRHeNe laser. Significant undercooling of the liquid silicon is observed during the cooling stage. The emissivity is almost constants during the melting period, but increases during the melting and solidification transformations.

The grain size of polycrystalline silicon by the excimer laser annealing (ELA) is primarily determined by the fluence, and the distribution uniformity is strongly influenced by the intensity fluctuation. Instead of the conventional CCD profile, a resist film is used to monitor the light intensity distributions over whole illumination area in submicron resolution. The high resolution measurements show speckle patterns with 0.1-0.15 spacing with maximum 10mJ/cm² variation. The fluctuation does not influence the grain size variation in the lateral growth region over 1-2 micrometers area, however, the undulation of intensity about 10mJ/cm² over 10 micrometers distance produces an appreciable changes in the grain sizes. Such a local temperature distribution corresponds to the envelop obtained by averaging small area, and is maintained during crystallization process.

The lattice strain in excimer laser crystallized polycrystalline Si thin films reflects the grain growth induced by the laser irradiation. In this report, the measurement of the lattice strain is made by using the energy-dispersive grazing-incidence x-ray diffraction with synchrotron radiation. The excimer laser crystallized poly- Si thin films show tensile lattice strain in the directions parallel to the substrate surface. The strain increases from 2.2 X 10^-3 to 5.0 X 10^-3 when the grain size increase from 40 to 200 nm. The strain is anisotropic between the strain and the strain in the layer near the substrate interface when the grain size is small. Carrier mobility in a thin film transistor tends to increase when the strain increases and the anisotropy decreases.

A novel approach for maskless deposition of numerous materials has been developed at the Naval Research Laboratory. This technique evolved from the combination of laser induced forward transfer and Matrix Assisted Pulsed Laser Evaporation (MAPLE), and utilizes a computer controlled laser micromachining system. The resulting process is called MAPLE-DW for MAPLE Direct Write. MAPLE-DW can be used for the rapid fabrication of circuits and their components without the use of masks. Using MAPLE-DW, a wide variety of materials have been transferred over different types of substrates such as glass, alumina, plastics, and various types of circuit boards. Materials such as metals, dielectrics, ferrites, polymers and composites have been successfully deposited without any loss in functionality. Using a computer controlled stage, the above mentioned materials were deposited at room temperature over various substrates independent of their stage, the above mentioned materials were deposited at room temperature over various substrates independent of their surface morphology, with sub-10micrometers resolution. In addition, multilayer structures comprising of different types of materials were demonstrated by this technique. These multilayer structures from the basis of prototype thin film electronics devices such as resistors, capacitors, cross-over lines, inductors, etc. An overview of the result obtained using MAPLE-DW as well as examples of several devices made using this technique is presented.

Presently, there is a going demand from the industry for microprocessing of materials. In particular, for application in the field of microsystem technology it is necessary to produce structures with dimensions down to the micrometer scale in various materials. We have been investigating the structuring of silicon, anodic bondable PYREX glass, Al₂O₃-ceramic and PMMA by means of laser microprocessing using an excimer laser and TEA CO₂ laser. Both the mask projection technique and the focusing technique have been employed. We will show the dependence of the ablation thresholds and the ablation rates on the laser parameters and on the physical properties of the materials, i.e. absorption coefficient, melting point and thermal conductivity. During and after the laser processing of different glasses we observed the formation of cracks in the laser irradiated region and partly in the glass wafer surrounding the drilled holes. Those crack formations should be due to the developed of thermally induced mechanical stress in the glass.

Ceramics like Si₃N₄, Al₂O₃ and ZrO₂ and also diamonds can be hardly machined by conventional methods. Short pulse lasers, especially frequency-tripled, diode pumped Nd:YAG-lasers with a high beam quality offer the possibility to ablate these materials with high quality. With a spot size of about 10 micrometers , high fluences can be achieved, so that the materials are vaporized without or with only a small holes with diameters >= 5 micrometers and cutting of thin ceramic substrates. The edges are sharp and the face of the cut is very smooth. Furthermore it is possible to ablate three dimensional microstructures. Therefore the laser beam is scanned over the surface and the materials is ablated pulse beside optimized machining parameters the surface roughness can be reduced to R <EQ 0.1 micrometers . Due to the low ablation rate of around 0.05 (mu) g/pulse the ablation depth of a single slice can be controlled very precisely. Depending on the material and the machining parameters the depth is in the range of 1 to 10 micrometers .

Ablation yields and thresholds for 193 nm UV laser ablation of ultrathin HfO₂ are presented. The single shot threshold fluence increases approximately linearly with HfO₂ thickness form 28 nm to 120 nm. Due to the logarithmic dependence of ablation depth on fluence this result with increasing layer thickness in an exponential increase of fluence necessary for clean ablation of the whole layer. The observed ablation depth for fixed HfO₂ thickness can be reproduced phenomenologically by taking ablation from the HfO₂ film as well as the quartz substrate into account. As a first approach to a quantitative understanding we calculate numerically the heat evolution in the layered system and identificate ablation with the onset of melting of the absorbing layer. Whereas the ablation curve for a 74 nm thick film can be reproduced that way, this is not the case for the case for the overall thickness dependence of the ablation threshold. This points to possible finite size effects for the phonon-phonon scattering rate in the thin dielectric layers.

We report precision micromachining of fused quartz and Pyrex glass by laser-induced plasma-assisted ablation (LIPAA) using a conventional nanosecond UV or visible laser. High- quality micrograting structures with periods of 1.06 and 20 micrometers using a phase mask and a mask projection technique, respectively were fabricated by LIPAA. The Fresnel zone pattern was also produced in fused quartz. The hole with the size of 700 micrometers in diameter was fast drilled in fused quartz and Pyrex glass. A possible ablation mechanism was discussed based on the dependence of ablation metal target and glass substrate.

Jefferson Lab is commissioning a high-average-power IR FEL during 1998. When driven with its superconducting linac operating in a recirculated mode, the IR Demo FEL is capable of producing kilowatt-level average power in the mid-IR range. With operational experience and hardware changes involving primarily change-out of the optical cavity mirrors, the FEL is capable of covering a wide range of the IR at power levels exceeding 100 watts. This tuning range combined with a unique pulse structure makes the Jefferson Lab FEL a versatile research and development tool for a wide variety of laser applications. A core group of industrial partners has been involved in planning applications using the FEL since 1991. This initial user group was augmented with university partners in 1993 and with participants from several national laboratories in 1996-1997. With the initiation of construction of the FEL and the associated 600 m² user facility laboratory in 1996, a number of topical user groups were formed to plan and implement the first series of user experiments. The industrial partners have formed user groups planning applications in polymer surface processing, metal surface processing, microfabrication, and electronic materials. University partners have submitted proposals, metal surface processing, microfabrication, and electronic materials. University partners have submitted proposals on basic science topics which complement and planned applied research topics, in addition to proposing experiments in atomic physics, chemical physics and materials science which take advantage of one or more of the unique characteristics of the FEL. A synopsis of the proposed user experiments for the first phase of operation of the Jefferson Lab FEL will be presented.

A diode-pumped laser system is described operating at 1 Hz-7 kHz repetition frequency. Average powers of more than 5 W at 355 nm are achieved. With it is beam quality of M² better than 1.1 it is excellently suitable for micro- machining applications generating smaller spot sizes with rather simple imaging system. Laser parameters such as pulse duration, average power as well as energy stability are investigated. Long term test results above 4.0 X 10¹⁰ shots are presented.

Mask based structuring in excimer laser applications is costly if mask with a small ratio of the hole pattern area compared to the whole illuminated area are used. In this case, the major part of the laser beam is reflected or absorbed at the mask. The herein presented system shapes the reflected part of the beam and guides it onto the mask again. This principle has been realized for up to eight irradiations of the mask. In order to achieve high quality ablation result both the beam divergence as well as the homogeneity play an important role. Therefore, a special homogenizer was developed which converts the excimer laser beam efficiency into a flat-top profile with negligible influence on the beam quality. The achieved optical resolution keeps within 2 micrometers and the homogeneity is sufficient to achieve nearly the same structure quality over the entire image field. Providing that the transmitting areas of the mask do not exceed a few per cent of the total irradiated area. An efficiency enhancement by more than a factor of five was achieved for eight mask irradiation passes compared to a single irradiation.

The condensation of vapor within the expanding plume produced by ns-laser ablation is discussed in the frame of Zeldovich and Raizer theory of condensation. The calculations have been performed for Si, Ge and C-vapors. It is shown that the size of clusters formed during the condensation is very small, typically of the order of few nanometers. The averaged cluster radius is calculated for different temperatures and densities of the initial plume. The generalization of the theory is made for inhomogeneous plume where the rates of nucleation as well as condensation times are different at different parts of the plume. The size distribution function is calculated for the plume expansion into vacuum. For the clusters moving together with vapor one can distinguish three different waves propagating through the plume: (1) The saturation wave, where the vapor becomes saturated, (2) The supercooling wave, where the highest supercooling is reached, and (3) The quenching wave, where the growth of cluster stops. The last stage of cluster formation is related to cooling of clusters and their crystallization. This leads to delay in photoluminescence signal with typical delay time from 0.1 to 7 ms depending on the type of the background gas and its pressure.

Nanocomposite thin films formed by metal or semiconductor nanocrystal (NCs) embedded in a host exhibit interesting nonlinear optical properties relate to the small size of the NCs. These properties make these materials potential candidates for the development of all-optical switching devices. The challenge is to produce nanocomposite materials with controlled and suitable characteristics. The present work aims to show that nanocomposite materials produced by pulsed laser deposition (PLD) might have superior structural and non-linear optical properties than those obtained by other techniques. This result will be illustrated in systems formed by metallic NCs embedded in an Al₂O₃ host. Fundamental aspects related to the nucleation and growth mechanisms or the reactivity of the NCs with the host will be discussed. Finally, the excellent nonlinear properties of the PLD synthesized composites will be illustrated in the case of Cu:Al₂O₃ films, in which the dependence of the nonlinear third order optical susceptibility has been investigated as a function of the NCs size and (chi) ⁽³) values as large as 10^-7 esu have been achieved.

Pulsed laser ablation (PLA) in inert background gases can synthesize the nanoscaled silicon (Si), for studying its material properties as one of the quantum confinement effects. We report an optimized condition in Si nanocrystalline formation by the PLA in inert background gas, varying processing parameters: pulse energy and width, inert background gas pressure. The optimized process can prepare well-dispersed Si nanocrystallites without any droplets and debris. Furthermore, we investigate the influence of the processing parameters Si nanocrystallites without any droplets and debris. Furthermore, we investigate the influence of the processing parameters on transition from amorphous-like Si thin films to nanocrystallites. It was found that there is a processing window of the inert background gas pressure where the carrier confinement effects become apparent. Next, we have fabricated electroluminescent (EL), diodes with active layers of the Si nanocrystallites. The structure of the EL diodes was semitransparent platinum electrode/Si nanocrystallite layer/p-type Si/Pt electrode. We have observed visible spectra of not only green photoluminescence, but also red EL, at room temperature. Furthermore, we have found that the EL diodes showed strong nonlinear dependence of EL intensity on current density.

Pulsed laser deposition of nitride semiconductor films offers an alternative to more usual techniques, such as MOCVD and MBE. PLD can produce good quality films at reduced growth temperatures. Rapid progress has been achieved in the laser few years, including demonstrations of epitaxial growth of GaN directly on sapphire. Work on PLD of direct- transition III- nitrides is briefly reviewed and our recent results for these materials are presented. Growth of these nitrides requires provision of nitrogen in a reactive form, which is usually supplied by NH₃ gas flow. With the approach described here, reactive nitrogen is provided in an atomic beam, which has the advantage of reducing dependence on substrate temperature to surmount the kinetic energy barrier for formation, while eliminating a source of hydrogen during growth. Films grown from ceramic GaN targets are compared with those grown from liquid Ga. The latter method can offer better control of unintentional doping. InN films were also grown directly from In metal targets, with very good results in term so stoichiometry and crystalline quality. AlN films were grown from ceramic AlN targets, with excellent texture at reduced temperatures. Results are presented for crystal structure, composition and surface morphology. Optical properties were studied by transmission and luminescence spectroscopy.

Advanced materials are being designed and tested for use on ball bearings that have wide-ranging applications in almost any type of spacecraft. There has been considerable interest in 'hard' or wear-resistant coatings for protecting steel surfaces present in bearing components. Titanium carbide (TiC) has received serious consideration as a wear-resistant coating material that could be suitable for use in such applications. At present, the commercially available process for the deposition of TiC involves heating the steel substrates to fairly high temperatures. High-temperature coating deposition is not desirable for applications involving steel substrates as it results in a softening of the steels. This further necessitates post-deposition heat- treatments for re-hardening the steel and re-polishing the coating. This paper will describe the use of Pulsed Laser Deposition (PLD) to deposit high-quality thin films of TiC on bearing steels at room temperature. Such a process eliminates the problems associated with high temperature deposition, and the costs and complexities involved in the post-deposition heat treatment of steels. To develop an understanding of the deposition process, the plasma generated by laser ablation has been investigated using time-resolved emission spectroscopy. The PLD of TiC films on bearing steels, the material properties of these films, and the spectroscopy of the ablated plume will be discussed.

Amorphous carbon films with variable sp³ content were produced by ArF pulsed laser deposition. An in-situ ion probe was used to measure kinetic energy of C⁺ ions. In contrast to measurements made as a function of laser fluence, ion probe measurements of kinetic energy are a convenient as well as more accurate and fundamental method for monitoring deposition conditions, with the advantage of being readily transferable for inter-laboratory comparisons. Electron energy loss spectroscopy and spectroscopic ellipsometry measurement reveal that tetrahedral amorphous carbon films with the most diamond-like properties are obtained at the C ion kinetic energy of approximately 90 eV. Film properties are uniform within a 12-15 degrees angle from the plume centerline. Tapping-mode atomic force microscope measurements show that films deposited at near- optimum kinetic energy are extremely smooth, with rms roughness of only approximately 1 angstrom over distances of several hundred nm. Field emission (FE) measurements show that ta-C does not appear to be a good electron emitter. After conditioning of ta-C films deposited on n-type Si a rather high turn-on voltage of approximately 50 V/micrometers was required to draw current of approximately 1 nA to the probe. The emission was unstable and typically ceased after a few minutes of operation. The FE tests of ta-C and other materials strongly suggest that surface morphology plays a dominant role in the FE process, in agreement with conventional Fowler-Nordheim theory.

We have investigated the emission spectra of a carbon plume generated from graphite by a visible pulsed laser for diamond-like coatings (DLC). The laser utilized was a 300- watt class copper vapor laser with a pulse duration of approximately 40 ns. To better understand the laser-target interaction, we have visualized plume dynamics near the graphite surface via Schelieren method. We found that the laser ablation process was accomplished with explosive material ejection during pulsed laser deposition (PLD). The ejection of material started at about 500 ns after the onset of laser pulse and lasted for about 10 microsecond(s) . The material ejection is very directional and introduced large amount of micro particulates in the DLC film. We have found that the use of a random phase plate to smooth the laser intensity profile effectively eliminated this ejection of material with additional advantage of higher coating rate. The spectra in the visible and UV of the plume emission were analyzed to correlate with DLC quality and coating rate. We have characterized the carbon plasma based on emissions from C, C₂, C⁺, and C⁺⁺ for laser peak intensities between 0.1 - 5 GW/cm² and 0.8 GW/cm². The kinetic energy of C⁺ was estimated to be approximately 20 eV at this optimized coating condition. We found that greater C⁺ kinetic energy at higher laser intensity does not necessarily produce better DLC. This process optimization enabled us to demonstrate a coating rate as high as 2000 micrometers -cm²/hr. The C₂ swan-band emission from the plume was most pronounced in the optimized coating condition and was used as a process diagnostic tool.

The problems of the atom beam formation and its application to the micro- and nanoelectronic manufacturing are considered. The method introducing a useful information into the structured atom beam and focusing this beam is described. This method named the atom projection is relevant to atom optics. Negative detuned laser radiation field controls the beam. Features of the cooling, structuring, information input, focusing processes are discussed. The scheme of the plant using the atom beam with adjustable density distribution. The atom beam cross-section and the processed area are shaped according to the desired profile. The scheme of the atom projector and the functions of its units are described. The spatial resolution of processing and the resolution of surface analysis are evaluated to be about 10 nm and 1 nm correspondingly. Presented process is maskless, in-situ, with high output rating. The atom projector can be applied for the manufacturing, analysis and in-line reconstruction of the IC as well as for basic researchers of matter. Authors consider the nanoelectronic chip manufacturing as the most perspective application for the atom projector.

We show that irradiation by the second harmonic (SH) of Ti:Sapphire femtosecond laser provides well-defined spots with micrometer diameter by controllable manner in pure PMMA. Combined effect of SH and fundamental frequency (FF) radiation of Ti:Sapphire laser yields significant decrease in recording time. These results relate to 3D bitwise optical information storage. Usually in order to produce irreversible detectable changes, either single amplified Ultra-Short Laser Pulse (USLP) irradiation of pure matrix or multi-shot irradiation of matrix with dyes by nonamplified USLP is employed. In our present experiments the 1.5 percent transformation of nonamplified Ti:Sapphire laser radiation into the Sh has been obtained by means of BBO crystal with thickness of 300micrometers . The SH beam was then focused within the PMMA matrix by a lens with NA equals 0.55. The onset of emission corresponds to the onset of detectable irreversible changes in PMMA detected by optical microscope. The SH provides two-photon electronic transition to the absorption band of PMMA. Theoretical analysis of experimental data shows that preliminary matrix excitation by SH is followed by a self-developing process. This process can be driven not only by SH radiation but by potentially more powerful FF radiation as well.

Laser texturing technique has been established to provide low flying height and low stiction required for manufacturing high storage density media. The characteristics of the laser bumps can be precisely controlled, and are critically important for the excellent tribological performance. In the study, the hard disks have been textured successfully using the argon ion laser with the aid of an acoustic-optic modular in the optical path. Alternative laser bumps can be formed with various bump shape and bump height. The topography of the laser bumps are observed using AFM. Laser bumps are formed because of the modification of laser beam on the substrate during the heating and cooling processes. In attempt to study the bump formation mechanisms, a photodiode was employed to detect the reflected and scattered laser light, which irradiates on the hard disk surface to form laser bumps. The detected signals were studied under various laser power and pulse duration. It was found that there is a good correlation between the detected signal and the laser bump characteristics. The system has been proved to be an effective and convenient method to study the laser bump formation processes, and to in situ diagnose the laser bump characteristics.

A pulsed UV laser based technique has been developed which permits the transfer, by direct-write exposure, of 3D image into a photosensitive glass/ceramic material. The exposed latent image volume is developed via temperature programmed bake process and then etched away using HF in solution. The height of the 3D microstructures is controlled by the initial laser wavelength used during the exposure and the time duration of the etching cycle. Using this technique we have fabricated large arrays of microstructures which have applications to microfluidics, microelectromechanical systems and optoelectronics. The resulting master copy can be used either as is or by use standard injection modeling techniques converted into a metallic or plastic copies. We present these results and others which have specific applications to miniature 1Kg class satellites - nanosatellites.

We describe the concurrent in-line inspection system, which controls the CO₂ laser drilling machine for printed wiring boards. The performance of a CO₂ laser drilling process was improved drastically by the introduction of this inspection system. The principle of this inspection systems is based on the relationship between the exposed bottom area of the inner layer copper foil in via hole and the intensity of the reflected laser beam. The end of drilling process is detectable by the saturation of the reflected laser beam intensity generate at the copper foil surface of the blind via hole. We have carried out the drilling process for glass-cored epoxy substrate and have observed that the productivity of the drilling process i increased by 30 percent due to this inspection system.

It has been studied the direct dry etching of GaAs/AlGaAs multilayer using argon ion laser. To analyze etching characteristics at an interface between GaAs and AlGaAs, local temperature profiles on the surface by a laser irradiation were calculated through 3D heat transfer equation. Etching profiles obtained in this study were somewhat different from that of GaAs bulk obtained in our previous study. Etch width of GaAs/AlGaAs interface was larger than that of the AlGaAs/GaAs. Now until, accurate mechanism of the dry etching for multilayer has not ben reported. But, it is assumed that the mechanism has to do with thermal characteristics such as thermal conductivity, absorption coefficient, and the mechanism has to do with thermal characteristics such as thermal conductivity, absorption coefficient, and melting point of materials. The phenomenon result from the fact that laser direct dry etching is dominantly thermal reaction. The maximum etching rate was 32.5 micrometers /sec and the aspect ratio of etched groove on multilayer was 0.5. This special etching profiles obtained in this study are expected to apply for a waveguide of optoelectronics and cantilever of MEMS.

Laser direct writing using thin solid films of metallo- organic precursors offers some unique advantages in terms of materials design, process control, and safety over gas phase or solution processor. Micro patterned copper films were obtained by laser-induced deposition using Cu(HCOO)₂ 4H₂O films as a precursor. Then the new applicabilities for interconnection of integrated circuits were preliminary studied by the estimation of physical and electrical properties of copper films after annealing. The growth kinetics of these Cu films was investigated as a function of the laser power and the scan speed which were varied in the range of 70 to 600 mW and 0.1 to 20 mm/s, respectively. The high-purity of the deposit was also confirmed by Auger electron spectroscopy analysis. The resistivity of the patterned copper films was a factor of about 20 higher than that of bulk value however, the resistivity decreased due to changes in morphology and porosity of the deposit and was about 10 (mu) (Omega) cm after annealing at 300 degrees C for 5 minutes.

In-situ excimer laser irradiation on growing films is expected to progress the surface reaction i.e. oxidation and surface migration of adatoms. This method therefore will be adequate for the low temperature formation of oxide semiconductor films showing a wide band energy gap. We studied the effect of in-situ excimer laser irradiation on the electron beam deposited Indium-Tin-Oxide (ITO) films and evaluated the electrical and optical properties. The ITO films deposited without laser irradiation at room temperature were opaque and had an amorphous structure, and its resistivity was higher than 0.04 (Omega) cm. On the other hand, the ITO films deposited with in-situ laser irradiation at room temperature showed good transparency and electric properties. The low resistivity, smaller than 9 X 10^-4 (Omega) cm, and high transparency, more than 90 percent, were achieved simultaneously at room temperature. The films crystallized with in-situ laser irradiation had a cubic crystalline structure. The Hall mobility and carrier density of the ITO film were 12 cm²/Vs and 5.5 X 10²² cm^-3, respectively. These result suggested that the in-situ excimer laser irradiation progressed the surface oxidation and eliminated the unstable adatoms on the surface of growing ITO films.

In the recent years, great progress in development of spontaneous UV and VUV sources, radiating on the transitions of excimer and exciplex molecules has been achieved. However, practical use of sealed-off excilamps is limited by low lifetime of gas mixture. In this paper, stability of output parameters of the excilamps pumped by glow, barrier and capacitive discharges is studied and the mechanism of chlorine losses in low pressure halogen containing excilamps made of quartz is determined.

A titanium target was ablated by a KrF excimer laser with fluences varying from 4 to 8 J/cm² in an argon filled environment with pressures ranging from vacuum to 1 torr. The effects of laser fluence and background gas pressure on the kinetic energies of the ablated species were investigated by temporally and spatially resolved emission spectroscopy. The maximum surface temperatures were calculated by a 1D conduction mode. Experimentally obtained surface temperatures from the kinetic energy of the ejected plume were one order of magnitude higher than the calculated temperatures. This discrepancy is most likely due to the absorption of laser energy by the plasma that is formed early in the pulse. Temporally resolved imaging with 10 ns gate width was also employed to reveal the evolution of the ablated plume against the background gas. Separation of slower and faster components were observed for exposures above 50 mTorr, and angular concentration of titanium in the plume was determined.

We describe the deposition of Ti:sapphire thin films by the pulsed-laser deposition (PLD) method for the waveguide laser application, with an emphasis on the reduction of droplets which is inevitably generate during PLD. In order to eliminate the droplets for the film surface, we introduced centrifugal separation of the droplets out of the laser ablation plume using a high-speed rotating target. The behavior of droplets in the ablation plume generated with a high-speed rotating target is presented along with the film properties.

For studying the material properties of nanostructured group IV materials, we have developed a pulsed laser ablation method into inert background gases. SiGe alloy nanocrystallites have possibility of novel band structure engineering by controlling not only compositions but also particle sizes. An ArF excimer laser was focused onto the surface of the powder-sintered Si_xGe_1-x target. During the laser ablation, He gas was introduced into a vacuum chamber and was maintained at a constant pressure. Size distribution of the Si_xGe_1-x ultrafine particles decreases with decreasing composition x under fixed conditions of deposition such as background gas pressure. Raman scattering spectra of the deposited SiGe ultrafine particles show three peaks ascribed to mixed crystalline SiGe after annealing, and the linewidths of the peaks broaden due to the reduced size of the crystallites. The frequencies and intensities of the peaks depend on the composition x. Visible PL spectra have broad peaks from 2.25 eV to 2.10 eV, at room temperature. The peak positions show blue shifts with increasing x. Electroluminescent diodes with the Si_0.8Ge_0.2 nanocrystallite active region were fabricated, and emit visible high peaked at around 1.8 3V, at room temperature.

Boron-Carbon-Nitride B_xC_yN_z thin films were deposited by excimer laser ablation of boron carbide under nitrogen ion-beam bombardment. Thin films were deposited in the intersection of the ablated B-C plasma and nitrogen ion beam on the silicon substrates. The laser pulse energy was selected in the range of 30-100 mJ with pulse duration of 23 ns. The electronic and compositional properties of the deposited thin films were analyzed by x-ray photoelectron spectroscope, Raman and IR spectroscope, scanning tunneling microscopy and ellipsometry measurements. The influence of the ion beam bombardment on the optical, electrical and electronic properties of the deposited thin films was studied.

GaN surface is clear etched by combination of KrF excimer laser irradiation and post chemical wet treatment using hydrochloric acid. KrF excimer laser irradiation ablates GaN surface and turns the ablated surface to Ga-rich layer. The Ga-rich layer is etched off by the hydrochloric acid treatment. X-ray photoelectron spectroscopy analysis reveals that the chemically etched surface has similar composition and chemical bonding to untreated GaN. The average roughness amazingly decreases to approximately 48 percent compared to the untreated GaN samples at the laser fluence increases beyond 1.5 J/cm².

The use of fluorine (F₂) lasers, emitting at 157 nm, offers new possibilities for key applications demanding very high resolution and/or higher photon energy to expand the laser-processable material spectrum. Promising results have been achieved using F₂ lasers at 157 nm for micromachining of various materials that are very difficult to process at other laser wavelengths. This paper reports about new F₂ laser source developments and their efficiency in processing Teflon/Polytetrafluoroethylene and fused silica under moderate, uniform illumination conditions. Ablation rates and threshold parameters have been investigated. Scanning electron micrographs of the produced microstructures are presented.