This PDF file contains the front matter associated with SPIE Proceedings Volume 6454, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Reproducible and sensitive elemental analysis of solid samples is a crucial task in areas of geology (e.g. microanalysis of fluid inclusions), material sciences, industrial quality control as well as in environmental, forensic and biological studies. To date the most versatile detection method is mass-spectroscopic multi-element analysis. In order to obtain reproducible results, this requires transferring the solid sample into the gas-phase while preserving the sample's stoichiometric composition. Laser ablation in combination with Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is a proven powerful technique to meet the requirements for reliable solid sample analysis. The sample is laser ablated in an air-tight cell and the aerosol is carried by an inert gas to a micro-wave induced plasma where its constituents are atomized and ionized prior to mass analysis. The 193 nm excimer laser ablation, in particular, provides athermal sample ablation with very precise lateral ablation and controlled depth profiling. The high photon energy and beam homogeneity of the 193 nm excimer laser system avoids elemental fractionation and permits clean ablation of even transmissive solid materials such as carbonates, fluorites and pure quartz.

Extreme ultraviolet lithography (EUVL) is the candidate for next generation lithography to be introduced by the semiconductor industry to HVM (high volume manufacturing) in 2013. The power of the EUVL light source has to be at least 115W at a wavelength of 13.5nm. A laser produced plasma (LPP) is the main candidate for this light source but a cost effective laser driver is the key requirement for the realization of this concept. We are currently developing a high power and high repetition rate CO₂ laser system to achieve 50 W intermediate focus EUV power with a Tin droplet target. We have achieved CE of 2.8% with solid Tin wire target by a transversely excited atmospheric (TEA) CO₂ laser MOPA system with pulse width, pulse energy and pulse repetition rate as 10~15 ns, 30 mJ and 10 Hz, respectively. A CO₂ laser system with a short pulse length less than 15 ns, a nominal average power of a few kW, and a repetition rate of 100 kHz, based on RF-excited, fast axial flow CO₂ laser amplifiers is under development. Output power of about 3 kW has been achieved with a pulse length of 15 ns at 130 kHz repletion rate in a small signal amplification condition with P(20) single line. The phase distortion of the laser beam after amplification is negligible and the beam can be focused to about 150&mgr;m diameter in 1/e². The CO₂ laser system is reported on short pulse amplification performance using RF-excited fast axial flow lasers as amplifiers. And the CO₂ laser average output power scaling is shown towards 5~10 kW with pulse width of 15 ns from a MOPA system.

In this paper a numerical simulation of laser hardening process is presented. The Finite Difference Method (FDM) was used to solve the heat transfer and the carbon diffusion equations for a defined workpiece geometry. The model is able to predict the thermal cycle into the target material, the phase transformations and the resulting micro-structures according to the laser parameters, the workpiece dimensions and the physical properties of the workpiece. The effects of the overlapping tracks of the laser beam on the resulting micro-structures is also considered. The initial workpiece micro-structure is taken into account in the simulation by a digitized photomicrograph of the ferrite perlite distribution before the thermal cycle. Experimental tests were realized on a C43 plate and the good agreement between the theoretical and experimental results is shown.

Cutting performance of a laser based hybrid technique on concrete was measured under different conditions, which are laser power (1-20kW), scan speed (1-100mm/s), laser beam diameter (5-10mm), and O₂ gas flow rate (0-50L/min).

First experiments on fundamental band CO lasing in sealed-off cryogenically cooled slab facility with RF discharge excitation were carried out. Repetitively pulsed and CW modes of RF discharge excitation were studied. The laser output characteristics for different slab geometries were compared. Average output power achieved 12 W. Lasing efficiency came up to ~14 %. The output laser spectrum was observed within wavelengths range 5.08-5.34 &mgr;m. Stable lasing was obtained for more than one hour.

Electra is a repetitively pulsed, electron beam pumped Krypton Fluoride (KrF) laser at the Naval Research Laboratory that is developing the technologies that can meet the Inertial Fusion Energy (IFE) requirements for durability, efficiency, and cost. Electra in oscillator mode has demonstrated single shot and rep-rate laser energies exceeding 700 J with 100 ns pulsewidth at 248 nm. Continuous operation of the KrF laser has lasted for more than 2.5 hours without failure at 1 Hz and 2.5 Hz. The measured intensity and energy per shot is reproducible in rep-rate runs of 1 Hz, 2.5 Hz and 5 Hz for greater than thousand shot durations. The KrF intrinsic efficiency is predicted to be 12% with measurements and modeling (Orestes Code). In addition we have compared Orestes with initial results of 23 J for the Electra Pre-Amplifier. The positive agreement between Orestes and our results lead allow us to predict that large KrF laser systems will meet the efficiency requirements for inertial fusion energy driver. The focal profile measurements show for single shot conditions recovery in less than 200 ms, the time needed for 5 Hz operation. Rep-rate focal profile measurements at 1 Hz show reproducibility in spatial extent and energy.

The way of transfer from CO small-scale model installation to industrial CO laser is proposed. A calculation model scaling of CO laser with RF discharge is developed. The calculation model is used for scaling small-scale experimental CO laser installation on which laser generation is received. It is proposed industrial CO laser for dismantlement of obsolete nuclear reactors and laser-hardening of working surfaces of railway rails. Estimated cost proposed CO laser makes several hundred thousand US dollars. Proposed CO laser can work without an optical cable due to installation of the laser head on the manipulator.

The multi-stage hybrid laser system producing ultrashort pulses of radiation with peak power ~10¹⁴ - 10¹⁵ W now under developing at the Lebedev Physical Institute of the Russian Academy of Sciences is discussed. The distinctive feature of the laser system is direct amplification of ultrashort pulses produced by solid state laser system, first going through a prism stretcher with negative dispersion, in gas active medium without using a rather expensive and complicated grating compressor of laser pulses. Two hybrid schemes are being developed now based on the amplification of femtosecond pulses of the third harmonic of Ti:Sapphire laser at the wavelength 248 nm in the active medium of KrF laser amplifier, and on the amplification of the second harmonic of Ti:Sa laser at the wavelength 480 nm in the active medium of photochemical XeF(C-A)-laser excited by VUV radiation of an e-beam pumped Xe₂ lamp. The final stage of the laser system is supposed to be an e-beam pumped facility with a laser chamber of 60 cm in diameter and 200 cm long in the case of KrF laser, and with another laser chamber of 30-40 cm in diameter put into the former one in the case of XeF(CA) laser. The parameters of such e-beam facility are close to those of previously developed at the Institute of High- Current Electronics: electron energy ~600 keV, specific input power ~ 300-500 kW/cm³, e-beam pulse duration ~ 100- 200 ns. A possibility of using Kr₂F as an active medium with saturation energy 0.2 J/cm² for amplification of ultrashort laser pulses is also under consideration. There was theoretically demonstrated that the energy of a laser pulse at the exit of the final stage of the laser system could come up to ~ 17 J with pulse duration ~50 fs in the case of KrF laser, and ~75 J with pulse duration of 25 fs in the case of XeF laser. Two Ti:Sa laser systems producing ~50 fs pulses with energy ~0.5 mJ at the wavelength 248 nm and ~5 mJ at the wavelength 480 nm have been already developed and are being now installed at the Lebedev Institute. Preliminary

We propose a new concept for a retro-directive tracking system applicable for communication and power transmission. In the proposed concept, the power transmitter utilizes a beacon emitted from the receiver to obtain information about its direction by conjugating its phase inside a nonlinear medium. Power is therefore transmitted back to the receiver by the phase conjugated beam. The power can be amplified by an array of phase conjugators which provides a large aperture so that the intensity can be increased on the receiver's photovoltaic panels compared to a single element. A system design provides the basic understanding of this setup and basic experiments are conducted with two Co-doped Sr_xBa_1-xNb₂O₆ (Co:SBN) crystals. We confirm the occurrence of interference of two beams that are generated by four wave mixing from a divergent signal beam. In areas of constructive interference, we could observe a higher intensity than the single non-interfering beams provides.

We have introduced the additional prepulse with main pulse to generate the stimulated Brillouin scattering (SBS) and investigated the effect of this technique. In general, temporal pulse shape deformation takes place when the pulse is reflected from the medium breeding SBS. This deformation of the SBS wave can cause optical breakdown in the optical components and consequently it leads to low reflectivity and low fidelity of the phase conjugated wave in the SBS medium. It has been shown that there is optimum prepulse time delay and minimum energy for preserving the SBS waveform. This method is so simple that it can be applied to other systems and utilized in many applications easily, such as high-power laser and optical isolator applications employing several SBS cells.

The beam combination technique using stimulated Brillouin scattering phase conjugate mirrors (SBS-PCMs) is one of the most promising technology to realize high energy/ high power/ high repetition rate. The beam combination technique using SBS-PCM can compensate any optical distortions occurred in the amplifier chain because it gives the phase conjugated wave for the good beam quality. In this paper we will introduce the cross type amplifier as a basic unit of the proposed beam combination system and show essential technology for realization of the beam combination system, such as the new SBS phase control technique proposed by the authors. These new techniques are the most simple among the phase locking techniques developed previously, and furthermore it is possible not only to lock but also to control the phases of the SBS waves very accurately.

The beam combination technique using stimulated Brillouin scattering (SBS) phase conjugate mirrors (PCMs) proposed by one of the authors, H. J. Kong, is a promising one for realization of high energy/power laser system with high repetition rate. However, phase controlling of the SBS waves is essentially required for beam combination system, since the SBS-PCM generates the random phase. Recently, we have achieved successful results for phase locking by the self-generated density modulation method. But it showed a long-term phase fluctuation due to the long-term fluctuation of the density of the liquid SBS medium. To compensate this long-term phase fluctuation, we have designed new phase stabilization system. In this paper, we will introduce this system and show successful experimental results.

We have found that it is possible to preserve the temporal waveform of the reflected wave generated from stimulated Brillouin scattering (SBS) by using a prepulse technique. In this work, the fundamental research has been carried out to preserve the deformed pulse shape reflected from SBS medium. It is well known that the reflected SBS wave has a steep rising edge. If one employs SBS cells in series, the rising edge of the pulse shape becomes steeper every time it reflects at every SBS cell. This deformation of the SBS wave can cause the undesirable effects when we employ several SBS cells in series, such as an optical breakdown in the optical components and the lower reflectivity and lower fidelity of the phase conjugated wave in the SBS medium. A prepulse energy of 5 mJ and a time delay of 5 ns have been measured to be the optimum values under this experimental condition. This prepulse method is useful in developing a multistage system employing several SBS cells in series for high-power laser applications.

We have demonstrated stable operation of a 2-kW Yb:YAG phase-conjugate master oscillator, power amplifier (PC-MOPA) laser system with a loop phase-conjugate mirror (LPCM). This is the first demonstration of a CW-input LPCM MOPA operating at a power greater than 1 kW with a nearly diffraction-limited output beam. The single-pass beam quality incident on the LPCM varied with the specific operating conditions, but it was typically ~ 20 times diffraction-limited (XDL). The measured beam quality with a MOPA output power of 1.65 kW was 1.3 XDL.

Microelectromechanical systems (MEMS) offer a promising approach for creating compact, efficient chemical oxygen iodine lasers. In this paper we report the demonstration and characterization of a chip-scale, MEMS-based singlet oxygen generator, or microSOG. The microSOG is a batch-fabricated silicon chip that is micromachined to form reactant inlets and distribution system, an array of microstructured packed bed reaction channels to ensure good mixing between the BHP and the chlorine, a gas-liquid separator that removes liquid from the output stream by capillary effects, integrated heat exchangers to remove the excess heat of reaction, and product outlets. The microSOG has successfully generated singlet delta oxygen, and the resulting singlet delta concentrations were measured in a quartz test cell downstream of the chip using absolutely-calibrated near-infrared emission measurements made by an InGaAs array spectrometer. A kinetics analysis was used to determine the concentration at the chip's outlet from the concentration at the measurement point. Singlet delta yield at the outlet was determined to be about 81% at 150 Torr plenum pressure with a 25 sccm flow of chlorine. The corresponding output flow carries about 1.4 W of power at the chip's outlet.

The electric oxygen-iodine laser (EOIL) concept uses an electric discharge plasma to generate an effluent flow containing singlet oxygen, O₂(a¹&Dgr;), and atomic oxygen, O, which react with I₂ to excite the atomic iodine laser transition at 1.315 &mgr;m. This chemically rich system has unique characteristics, whose understanding requires systematic chemical kinetics investigation under carefully selected conditions to isolate the key reaction mechanisms. We describe a series of reacting flow measurements on the reactions of discharge-excited active-O₂ with I₂, using a comprehensive suite of optical emission and absorption diagnostics to monitor the absolute concentrations of O₂(a¹&Dgr;), O₂(b¹summation), O(³P), O₃, I₂, I(²P_3/2), I(²P_1/2), small-signal gain, and temperature. These multispecies measurements help to constrain the kinetics model of the system, and quantify the chemical loss mechanisms for I(²P_1/2).

Laser oscillation at 1315 nm on the I(²P_1/2) → I(²P_3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O₂(a¹&Dgr;) produced using a low-pressure oxygen/helium/nitric-oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O₂(a¹&Dgr;) generation system. The advanced model BLAZE-IV has been introduced in order to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O₃, O₂(b¹&Sgr;), and O atom, and gas temperature measurements, but is under-predicting the increase in O₂(a¹&Dgr;) concentration resulting from the presence of NO in the discharge. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O₂(a¹&Dgr;) concentrations downstream of the discharge in part via a recycling process, however there are still some important processes related to the NO_X discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics.

The mechanism by which I₂(B) is excited in the chemical oxygen-iodine laser was studied by means of emission spectroscopy. Using the intensity of the O₂(b¹&Sgr;,&ngr;'=0) → O₂(X³&Sgr;,&ngr;''=0) band as a reference, I₂(B) relative number densities were assessed by measuring the I₂(B,&ngr;')→ I₂(X,&ngr;") emission intensities. Vibrationally excited singlet oxygen molecules O₂(a¹&Dgr;, &ngr;'=1) were detected using IR emission spectroscopy. The measured relative density of O₂(a¹&Dgr;,&ngr;'=1) for the conditions of a typical oxygen-iodine laser medium amounted to ~15% of the total O₂ content. Mechanisms for I₂(B) formation were proposed for both the I₂ dissociation zone and the region downstream of the dissociation zone. Both pumping mechanisms involved electronically excited molecular iodine I₂(A', A) as an intermediate. It has been suggested that, in the dissociation zone, the I₂ A', and A states are populated in collisions with vibrationally excited singlet oxygen molecules O₂(a¹&Dgr;,&ngr;'). In the region downstream of the dissociation zone the intermediate states are populated by iodine atom recombination process. I₂(B) is subsequently formed in collisions of I₂(A',A) with singlet oxygen. We also conclude that I₂(B) does not participate measurably in the I₂ dissociation process and that energy transfer from O₂(b¹&Sgr;) does not excite I₂(B) to a significant degree.

In the present study we have observed rapid quenching of O₂(a¹&Dgr;) in O(³P)/O₂/O₃ mixtures. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O₂(a¹&Dgr;) quenching were followed by observing the 1268 nm fluorescence of the O₂ a¹&Dgr;-X³&Sgr; transition. The temporal profiles of oxygen atoms O(³P) were monitored by means of the O+NO chemiluminescent reaction. The mechanisms of fast O₂(a¹&Dgr;) quenching in the presence of O atoms are discussed.

An efficient Cesium vapor laser pumped with a continuous wave narrowband Laser Diode Array (LDA) has been demonstrated. To obtain a high lasing efficiency, it is necessary to narrow the linewidth of the pumping LDA to match the Cs atom absorption line. An external cavity with holographic grating was used to narrow the linewidth of a commercially available LDA to a value of 11 GHz that matches the Cs vapor absorption line broadened by a buffer gas at atmospheric pressure. The developed pump source was used for pumping a Cs vapor laser, which operated at 894 nm. Preliminary experiments yielded 400 mW output power and about 20% slope efficiency. The laser efficiency can be significantly increased by optimizing the cell and cavity design and matching the pump beam to the cavity mode size.

The Solid-State, Heat-Capacity Laser (SSHCL) program at Lawrence Livermore National Laboratory is a multi-generation laser development effort scalable to the megawatt power levels with current performance approaching 100 kilowatts. This program is one of many designed to harness the power of lasers for use as directed energy weapons. There are many hurdles common to all of these programs that must be overcome to make the technology viable. There will be a in-depth discussion of the general issues facing state-of-the-art high energy lasers and paths to their resolution. Despite the relative simplicity of the SSHCL design, many challenges have been uncovered in the implementation of this particular system. An overview of these and their resolution are discussed. The overall system design of the SSHCL, technological strengths and weaknesses, and most recent experimental results will be presented.

A promising avenue in the development of pulsed chemical HF/DF lasers and amplifiers is the utilization of a photonbranched chain reaction initiated in a two-phase active medium, i.e., a medium containing a working gas and ultradispersed passivated metal particles. These particles are evaporated under the action of IR laser radiation, which results in the appearance of free atoms, their diffusion into the gas, and the development of the photon-branching process. The key obstacle here is the formation a relatively-large volume (in excess of 10³ cm³) of the stable active medium, and filling this volume homogeneously for a short time with a sub-micron monodispersed metal aerosol, which has specified properties. In this manuscript, results are presented for an extensive study of a gas-dispersed component of a H₂-F₂ laser active medium, including novel techniques for the formation of a two-phase active medium with specified properties; aerosol optics; degradation of the dispersed component; and beam stability of a chemically-active aerosol. These results should help lead the way to creating powerful, reliable and inexpensive self-contained pulsed sources of coherent radiation with high energy, high laser beam quality, and the possibility of scaling up the output energy.

The forced air Turbo Heat Sink / THS [1], an effective cooler for electronics, handles large flows of air and energy. AlN, a ceramic, sports low TCE and a good thermal conductivity; the deep, curved air-cooling channels are milled before firing; later, to suit an automated assembly, precision grinding forms a mounting plane with more linear grooves. The mounting plane solders directly the Laser Diodes / LD and a full fledged hybrid electronics, while the shallow grooves, part of a semi-kinematic positioning, locate accurately the coupling optics. Those AlN THSs are available up to &fgr;⩽300mm. Co-integrating optics with the driving electronics compacts the system. The on board &mgr;Processor with IOs programs currents and timings, logs temperatures and powers, compensates ageing. Running much hotter than the LDs, the digital and power dices are better rim mounted. The planar top of a THS solder mounts a large field of well spaced LDs, bars or single channel; this direct dice assembly at low density cuts the thermal losses to extend the operating life; at the same time it improves the emitted beams. Few shared optical elements collimate each beam, moderately elliptical and large as possible. In front of each row of LDs, a shallow groove seats a long cylindrical lens and a prism; both correct the astigmatism and bend upward the expanding rays. Above, an array of cylindrical and spherical lenses collimates collectively each expanding beam. Finally, a large hollow mirror focuses the pumping energy on the lasing rod; its conical or bell shape uniforms the feed intensity with an optimal, narrow range of incidence angles. The AlN THS and the grooves position the optical shaping elements on a regular matrix; this radial or parallel order needs simple methods to assembly few low-cost parts. The output window closes the hermetic chamber. Adapting the final coupling optics, the same light generating engine can side etc feed a lasing slab.

This paper refers to the development of a numerical simulator for Laser Milling process useful for industrial applications able to predict the machining results when different materials are processed, different surface conditions are encountered and spatial and temporal distributions of the pulsed beam are set. The original software presented, developed by the authors, are well suited for simulating laser milling or laser micromachining operations with power density up to 10¹⁴ W/m² and pulse duration in the order of nanoseconds. The temperature of the solid phase is evaluated by solving the Fourier equation by using the finite difference method (FDM). The recession velocity of the ablating surface is evaluated according to the Hertz-Knudsen equation assuming that the explosive effects are negligible. The plasma plume is considered in local thermodynamical equilibrium (LTE) and the energy balance permits to evaluate the plume temperature, ion distribution and pressure under the assumption that the gas expansion, from the surface target, produces a sonic front. The plume energy balance is influenced by the energy lost for irradiation from the plume and by the quantity of laser beam energy reflected from the target surface. Numerical simulations have been conducted to quantify this influence on the plasma plume physical state and, consequently, on the ablation process considering a Nd:YAG diode pumped source and three different target materials: Fe-C alloy, copper and aluminum.