High-power Excimer Research Articles

Studies in fiber guided excimer laser surgery for cutting and drilling bone and meniscus.

Our experiments on transmitting high-power excimer laser pulses through optical fibers and our investigations on excimer laser ablation of hard tissue show the feasibility of using the excimer laser as an additional instrument in general and accident surgery involving minimal invasive surgery. By combining XeCl-excimer lasers and tapered fused silica fibers we obtained output fluences up to 32 J/cm2 and ablation rates of 3 microns/pulse of hard tissue. This enables us to cut bone and cartilage in a period of time which is suitable for clinical operations. Various experiments were carried out on cadavers in order to optimize the parameters of the excimer laser and fibers: e.g., wavelength, pulse duration, energy, repetition rate, fiber core diameter. The surfaces of the cut tissue are comparable to cuts with conventional instruments. No carbonisation was observed. The temperature increase is below 40 degrees C in the tissue surrounding the laser spot. The healing rate of an excimer laser cut is not slower than mechanical treatments; the quality is comparable.

Generation of high peak power excimer laser radiation by pulse shortening

Techniques for shortening the pulses of a commercial oscillator-amplifier excimer laser have been investigated. By a combination of a H2-Raman cell and a saturable absorber dye jet the oscillator pulses are shortened from about 25 ns to typically 1.5 ns. Upon amplification pulses around 3.5 ns with peak powers of more than 100 MW for KrF (248 nm) and 25 MW for XeCl (308 nm) are obtained.

Super-polished silicon carbide mirror for high-power operation of excimer lasers in a vacuum ultraviolet spectral range

We demonstrate the usefulness of a high-quality SiC mirror for the high-power operation of vacuum ultraviolet lasers. A void free SiC film of 400-μm thickness was deposited onto a high-purity graphite substrate by chemical vapor deposition. The super-polished SiC mirror, whose surface roughness was 0.2 nm rms, was used as a cavity reflector of a high-power Ar excimer laser, which operates at 126 nm. The highest output energy of 400 mJ/cm2 per pulse, which corresponds to the energy density of 1 J/cm2 on the SiC mirror surface, has been obtained without any damage to the SiC mirrors.

Development of a high-power ultra-short pulse excimer laser in the Max-Planck-Institut.

Development of a high-power ultra-short pulse excimer laser in the Max-Planck-Institut.

A high-power long pulse excimer laser

Excimer lasers operating at high average powers are becoming important for materials-processing applications. A long-pulse excimer laser with automatic spark preionization which provides a pulse energy of 1 J with an optical pulse length of 200 ns full-width half-maximum for XeCl is described. Successful scaling of the repetition rate to 220 p.p.s. is discussed along with requirements for gas flow. >

1-ns high-power high-repetitive excimer laser oscillator

A 1-ns high-power high-repetitive excimer laser oscillator has been developed for which the peak power obtained was more than 1 MW with 1-ns pulse width for both XeCl and KrF gas mixtures. The characteristic output power per unit active volume is calculated to be more than 2 GW/L, which is nearly one order larger than that extracted from usual discharge devices. It is inferred that the gain depletion in the active medium under such an extremely large output power condition has led to successful pulse shortening. The device can be operated at a repetition frequency of at least 500 Hz without a gas circulation system. The beam divergence was reduced to near the diffraction limit, although the oscillated-pulse width is only 1 ns.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pulsed Laser Cleaning of Antimony Single Crystal &lt;111&gt; Surface

ABSTRACTThe&lt;111&gt; face of an antimony single crystal was irradiated under ultra-high-vacuum conditions by the 193 rn radiation of a high-power excimer laser. The effects of the laser beam on the sample as a function of the light Energy Density (ED) and of theannealing Repetition Number are presented.Surface studies by Auger electron spectroscopy, scanning electron microscopy and low energy electron diffraction show that an atomically clean and well ordered surface can be produced by t is method. A strong chemical reduction is induced by pulsed aser annealing above 100 to 130 mI/cm2. Surface analysis shows that, for an ED less than 500 mJ/cm2 the surface evaporates without melting deeper than 200 rim. Evidences for oxide modification and for organic molecule desorption were observed even after irradiations with an ED as low as 45 mJ/cm2.The surface reduction is described by a thermal model involving surface heating and subsequent evaporation of the oxide layer. The desorption and diffusion processes may involve both thermal and photolytic mechanisms.

High-power excimer lasers and new sources of coherent radiation in the vacuum ultraviolet

1. Introduction 1031 2. Generation of powerful ultrashort pulses of ultraviolet radiation with excimer lasers 1032 3. Generation of high harmonics and nonlinear frequency mixing in atomic and molecular gases 1034 4. Multiphoton pumping of atoms and molecules with subsequent stimulated emission in the vacuum ultraviolet region 1036 5. Lasers based on anti-Stokes Raman scattering 1037 6. Conclusions 1039 7. References 1040

Tunable oscillation of a high-power argon excimer laser in the vacuum-ultraviolet spectral region

Successful oscillation of a tunable, high-power argon excimer laser is reported. The wavelength was tuned from 124.5 to 127.5 nm with a spectral width of 0.3 nm. The output power of 2.2 MW, obtained at the line center, is 3 orders of magnitude larger than the value reported previously by Wrobel et al. [Appl. Phys. Lett. 36, 113 (1980)]. The possibility of frequency conversion of the argon excimer laser radiation to other wavelengths by a stimulated Raman scattering process is discussed.

Moshchnye eksimernye lazery i novye istochniki kogerentnogo izlucheniya v vakuumnom ul'trafiolete

Moshchnye eksimernye lazery i novye istochniki kogerentnogo izlucheniya v vakuumnom ul'trafiolete

High-power argon excimer laser at 126 nm pumped by an electron beam

A high-power argon excimer laser has been developed with an output power exceeding 2 MW in the VUV region at 126 nm. As an alternative to a conventional Al/MgF(2)-coated mirror, which was susceptible to damage, an uncoated quartz plate was successfully used as a reflector for reproducible high-power operation of the argon excimer laser without any mirror damage. Observation of the temporal behavior of the laser pulse in relation to that of the gain coefficient is discussed.

Investigation of dye lasers excited by high-power KrF laser radiation

An investigation was made of the lasing characteristics of ethanol solutions of the dyes rhodamine 6G (R6G), coumarin 47 (C47), p-terphenyl (PTP), and POPOP pumped by high-power KrF laser radiation (λ = 248 nm) pulses of up to 10 J energy and 80 nsec duration. A laser output energy of 1.1 J at an efficiency of 14% was obtained from the R6G and C47 solutions. The optical strength of the R6G and C 47 solutions at the pump radiation wavelength was determined. The construction of dye lasers pumped by high-power excimer laser radiation was considered.

Saturation of resonant third-harmonic generation due to self-defocusing and a redistribution of the population densities

Using a high-power excimer laser, pumped dye laser third-harmonic generation in strontium was investigated around several two-photon resonances for input intensities which are well above the onset of saturation. The dominant role of self-defocusing and of the time-dependent redistribution of the population densities is demonstrated. Strong stimulated emission on several transitions branching off from the excited state of the two-photon resonance and several competing parametric processes have been observed. Good agreement is obtained with a theoretical model which accounts for the redistribution of the population densities and which shows the importance of the ac Stark effect for the central structure of the high-intensity conversion profiles.

Injection-locking unstable resonator excimer lasers

We review the basic criteria for effective and efficient injection locking of high-power excimer lasers, and enumerate the various parameters of practical concern for experimental implementation. Various injection schemes are compared and the fundamental limitations of the process are covered. Corroborative experimental results are also reviewed, and applications made possible by injection locking are discussed.

Plasma-surface interaction studies using laser resonance scattering

Results of systematic plasma-surface interaction studies by laser resonance scattering are presented. Conventional laser sources have been used to obtain improvements in metallic atom detection of (i) absolute calibration of the optical system, (ii) velocity-distribution function measurements, and (iii) angular distribution measurement of sputtered atoms by ion-beam bombardment. In addition, wide-range (from vacuum UV to visible) tunable sources have been developed based on a high-power excimer laser. Single-shot velocity-distribution function measurements are also described using a fast-frequency scan dye laser.

Deep uv submicron lithography by using a pulsed high-power excimer laser

Deep uv lithography by using a pulsed high-power excimer laser is demonstrated, in which submicron patterns with high resolutions were fabricated on PMMA (polymethyle methacrylate) photoresists by laser irradiation for 20 ns.

Ultrafast deep UV Lithography with excimer lasers

The use of high-power pulsed excimer lasers for photolithography is described for the first time. Short exposure times, high resolution and absence of speckle are experimentally demonstrated. Using a XeCl laser at 308 nm and a KrF laser at 248 nm, excellent quality images are obtained by contact printing in two positive photoresists. Resolution down to 1000 line-pairs/mm is demonstrated. These images are comparable to state-of-the-art lithography done with conventional lamps; the major difference is that the excimer laser technique is ∼ 2 orders of magnitude faster. Preliminary results on reciprocity behavior in several resists are also presented.

Ultrafast High-Resolution Contact Lithography with Excimer Lasers

A new technique for speckle-free, fine-line high-speed lithography using high-power pulsed excimer lasers is described and demonstrated. Use of stimulated Raman shifting is proposed for obtaining the most desirable set of spectral lines for any resist. This permits, for the first time, the optimization of the exposur wavelengths for a given resist, rather than the reverse situation. Excellent-quality images are obtained in 1-µm-thick diazo-type photoresists such as ® AZ-2400 and a diazonaph-thoquinone-®Novolak resist system by means of contact printing with a XeCl laser at 308 nm and a KrF laser at 248 nm. Resolution down to 1000 line pairs per millimeter is experimentally demonstrated. These images are comparable to state-of-the-art contact lithography obtained with conventional lamps. The major difference is that the excimer laser technique is approximately two orders of magnitude faster. Tests on reciprocity failure ins everal resists indicate a decrease in sensitivity by only a factor of three, despite the ≅108 times larger power density used in the laser exposures. The possibility of photochemical reactions being diflerent from those taking place in the case of lamp exposures is discussed in view of these results.

High-Power XeCl Excimer Laser by Discharge Pumping

High-Power XeCl Excimer Laser by Discharge Pumping