D.W. Coutts

UV laser ablation and irm-GCMS microanalysis of 18O/16O and 17O/16O with application to a calcium-aluminium-rich inclusion from the Allende meteorite

Abstract Analyses of 18O/16O and 17O/16O in silicate and oxide minerals by UV laser ablation of 100 × 80 × 50 μm sample pits combined with irm-GCMS yield precision and accuracy similar to that of conventional methods. This represents a 100-fold reduction in minimum size relative to other fluorination methods based on gas-source mass spectrometry and enables high-precision in-situ intracrystalline analysis of silicate minerals. Analyses of almandine, forsterite, and schorl of known isotopic compositions indicate an analytical precision of ±0.3‰ (1σ) in δ18O and ±0.4 in δ17O with an accuracy of similar magnitude. Application to meteoritic samples is demonstrated by in-situ analysis of pyroxene and melilite from a type B CAI inclusion from the Allende meteorite. The CAI data adhere to the carbonaceous chondrite anhydrous mineral line defined by conventional macroscopic fluorination methods and demonstrate that non-mass dependent differences of 1‰ amu−1 are discernible. The unique combination of analytical and spatial resolution afforded by the new UV laser microprobe will allow high-precision mapping of the distribution of anomalous oxygen in minerals from calcium-aluminum-rich inclusions on a previously unattainable scale.

Double-pass copper vapor laser master-oscillator power-amplifier systems: generation of flat-top focused beams for fiber coupling and percussion drilling

In this paper, a compact master-oscillator power-amplifier laser system incorporating telescopic beam expansion in a high-gain double-pass amplifier is presented. A miniature (0.5 W) master-oscillator copper vapor laser is used to efficiently extract over 37 W of high-beam-quality (full transverse coherence) output power from a kinetically enhanced nominally 35-W copper vapor laser at 12-kHz pulse repetition frequency. By configuring the oscillator for low coherence output and using a multimode optical fiber between the oscillator and the double-pass amplifier, a high-power (34 W) low-divergence output beam having a well-defined flat-top far-field beam profile was also produced. The flat-top farfield beam profile arises from control of the spatial coherence of a flat-top near-field beam, rather than the usual techniques for producing flattened Gaussian beams from coherent Gaussian beams. Use of the flat-top focused beam for high-speed percussion drilling of high quality 100-/spl mu/m diameter holes in metals was demonstrated, as well as high-power (34-W average power, 80-kW peak power) damage-free power transmission through 100-/spl mu/m core diameter step-index optical fibers.

High-repetition-rate polymeric solid-state dye lasers pumped by a copper-vapor laser

We report on the laser action of pyrromethene 567 incorporated into polymeric matrices and pumped longitudinally with the green line of a copper-vapor laser. When the dye was dissolved in a copolymer of methyl methacrylate and pentaerythritol triacrylate, 290 mW average power at 1 kHz (37% lasing efficiency) was obtained. The laser output decreased to 150 mW after 30 min irradiation time (1.8×106u200ashots) and to 32 mW after 70 min of operation (4.2×106u200ashots). Output power of up to 1 W at 6.2 kHz was obtained for short periods of time. Polymeric matrices incorporating rhodamine 6G were also studied.

High average power blue generation from a copper vapour laser pumped titanium sapphire laser

A high power (6.2 W) titanium sapphire laser pumped by a high beam quality copper vapour laser (CVL) at 6.2kHz has been demonstrated. The high beam quality copper vapour laser consisted of a small-scale master oscillator and a double-pass power amplifier giving nearly 20 W output with better than 2 times diffraction-limited beam quality. Up to 5.0 W of narrowband 780nm output was obtained from a ring Ti:sapphire laser when seeded with a 7mV CW single mode diode laser. Wavelength tuning of an astigmatically compensated Z-cavity Ti:sapphire laser using up to four intracavity Brester prisms yielded up to 3.3output at 920nm, and up to 1.8 W blue output at 460 nm then frequency doubled in an intracavity LBO crystal.

Method for determination of the volume of material ejected as molten droplets during visible nanosecond ablation

A novel method is presented for determining the volume of molten material ejected from a substrate as a result of visible pulsed-laser ablation. A 100-microm-wide pulsed-laser light sheet (tau approximately 5 ns, lambda = 532 nm) was used in conjunction with a CCD camera to provide high-speed cross-sectional images of single-pulse ablation of aluminum with a visible nanosecond laser source. Computational analysis of the two-dimensional gray-scale images was used to determine the total volume of material ejected from the substrate in the form of molten droplets. Ablation with dual-wavelength (511- and 578-nm) pulses of 30-ns duration was characterized under various fluence conditions (0-25 J cm(-2)), allowing a quantitative threshold for explosive melt ejection in aluminum to be established at approximately 10 J cm(-2). The temporal evolution of the ejected material showed that, for an incident fluence of approximately 40 J cm(-2), molten-droplet ejection commenced at approximately 400 ns and ceased after approximately 2 micros.

Progress in high-speed UV micro-machining with high repetition rate frequency-doubled copper vapour lasers

We report on progress in uv micro-machining with high repetition rate (4.5 kHz) frequency-doubled copper vapour lasers (CVLs). Characteristics of drilling 2 to 300 micron diameter holes in several materials, including polyethylene and polyimide, will be discussed.We report on progress in uv micro-machining with high repetition rate (4.5 kHz) frequency-doubled copper vapour lasers (CVLs). Characteristics of drilling 2 to 300 micron diameter holes in several materials, including polyethylene and polyimide, will be discussed.

Plasma kinetics issues for repetition rate scaling of kinetically enhanced copper vapour lasers

The performance of a small-scale KE-CVL operating at a pulse repetition rate of 50kHz has been investigated by comparing modelling results and experimental data to understand the underlying plasma kinetics issues for pulse repetition rate scaling. Comparison between initial modelling predictions and experimental results relating to the laser output power and the population densities of the metastable lower laser levels (Cu* 4s2 2D3/2,5/2 ) suggests that there is an additional de-excitation mechanism for the metastables in the KE-CVL. The most likely de-excitation mechanism involves vibrationally-excited H2(v) molecules Cu*2D+H2(v) => CuH+H. A rate-coefficient of 2x10-16m3s1 is obtained by comparing modelling results with experimental data relating to the laser output power and the time-evolution of the axial 2D3/2 metastable population density.

Kilohertz pulse repetition frequency slab Ti:sapphire lasers with high average power (10 W)

High-average-power broadband 780-nm slab Ti:sapphire lasers, pumped by a kilohertz pulse repetition frequency copper vapor laser (CVL), were demonstrated. These lasers are designed for damage-free power scaling when pumped by CVLs configured for maximum output power (of order 100 W) but with poor beam quality (M(2) approximately 300). A simple Brewster-angled slab laser side pumped by a CVL produced 10-W average power (1.25-mJ pulses at 8 kHz) with 4.2-ns FWHM pulse duration at an absolute efficiency of 15% (68-W pump power). Thermal lensing in the Brewster slab laser resulted in multitransverse mode output, and pump absorption was limited to 72% by the maximum doping level for commercially available Ti:sapphire (0.25%). A slab laser with a multiply folded zigzag path was therefore designed and implemented that produced high-beam-quality (TEM(00)-mode) output when operated with cryogenic cooling and provided a longer absorption path for the pump. Excessive scattering of the Ti:sapphire beam at the crystal surfaces limited the efficiency of operation for the zigzag laser, but fluorescence diagnostic techniques, gain measurement, and modeling suggest that efficient power extraction (>15 W TEM(00), >23% efficiency) from this laser would be possible for crystals with an optical quality surface polish.

On Pulsed Laser Ablation of Metals: Comparing the Relative Importance of Thermal Diffusion in the Nanosecond - Femtosecond Regime

Objectives Ths TMR programme ((EREIFMRXcN80188) aims to study the fundamental physical and chemical asps of pulsed laser-solid inleraetlons lading to any form of surface cleaning in ader (0 develop the l ax r cleaning technique as a reliable industrial production ml. h c r cleaning appears to be a suitable replacement fM Solvent based iechniques in a wide range of domains covenng from the semimnductor technology to the nuclear technology. Pulsed laser irradiation (few nanoseconds or shorter) of high energy will be applied an a large range of wavelengths (from UV to IR) for cleaning of vaious kinds of pl luted or mntamimkdsubsmies e.g. merallic surface plymenc surlacc ceramic surface sIone ... Methods using lm to ;lean and Io ppre ~u&ces can be deli&rcd relatively f& large fields ofapplicationsconceming various mateialsorenginceing pocesses like: i) Metals, Insulators, Polymers. ii) Semiconductor Technology. ni) Hostile Environments (nuclear technology), iv) Restoration of An Work.. .

Influence of temperature-dependent excited state absorption on a broadly tunable UV Ce:LiLuF laser

We report the experimentally measured polarized small signal gain for Ce:LiLuF at 309 nm and 327 nm. The gain was found to be anisotropic and temperature dependent. Using a rate equation based model we have simulated the affect of excited state absorption (ESA) on the small signal gain in Ce:LiLuF. As a result we report the polarized emission and ESA cross-sections for Ce:LiLuF at 309 nm and 327 nm. We show the ESA to be temperature dependent and consequently demonstrate that ESA is the cause of the change in small signal gain with temperature in Ce:LiLuF. Further, we experimentally show the decrease, with temperature, of the ESA cross-sections at 309 nm causes a 70% increase in the laser output at 309 nm. We demonstrate how the introduction of a σ-biased loss into the cavity suppresses σ-polarized lasing at 327 nm. This counteracts the decrease in laser output below ~10°C caused by the anisotopic nature and temperature dependence of the ESA in Ce:LiLuF at 327 nm.