Peter Langston

Point defects in Sc 2 O 3 thin films by ion beam sputtering

We show that the concentration of oxygen interstitials trapped in Sc2O3 films by ion beam sputtering from metal targets can be controlled by modifying deposition conditions. We have identified point defects in the form of oxygen interstitials that are present in Sc2O3 films, in significantly high concentrations, i.e., ∼10(18)  cm(-3). These results show a correlation between the increase of oxygen interstitials and the increase in stress and optical absorption in the films. Sc2O3 films with the lowest stress and optical absorption loss at 1 μm wavelength were obtained when using a low oxygen partial pressure and low beam voltage.

Influence of process conditions on the optical properties of HfO2/SiO2 coatings for high-power laser coatings

We investigate the variations that occur with changes in the number of layers and with the use of the assist beam main and assist beam energy on the morphology of HfO2/SiO2 quarter wave stacks deposited by dual ion beam sputtering. We show how the addition of sequential HfO2/SiO2 bilayers, up to eight, affects the surface roughness and micro-crystallinity of the top HfO2 layer. We also show that use of the assist source significantly smooths the surface while simultaneously reducing microcrystallinity. The HfO2/SiO2 structures are very robust and can withstand fluences in excess of 3 J/cm2 generated by 1ps pulses from a chirped amplified Ti:Sapphire laser.

Advances in ion beam sputtered Sc2O3 for optical interference coatings

Scandium oxide is an attractive candidate for the engineering of interference coatings, although not widely explored. This paper describes the ion beam sputtering of Sc2O3. It is shown that the structural properties of the material are affected by the deposition conditions. Laser damage in different regimes of pulsewidths is investigated. These results show that the 1-on-1 laser damage fluence, in both the thermal and deterministic regimes, varies with deposition conditions but this is not the case for S-on-1, indicating that laser-induced defects are important.

What role do defects play in the laser damage behavior of metal oxides

We have investigated the role of native point defects in the laser damage behavior of amorphous thin films of Sc2O3 deposited by ion beam sputtering. Through systematic characterization and detailed modeling we show that native defects influence the 1-on-1 laser induced damage threshold fluence of the Sc2O3. This effect, as shown by the model and confirmed by experiments, is pulse duration dependent.

Ion beam sputtered Y2O3

We have investigated the ion beam sputtering (IBS) of Y2O3 as an alternative to HfO2 for high index layers in interference coatings for high power lasers. We present results on structural and optical properties of Y2O3 deposited from an oxide target. The IBS Y2O3 films are amorphous with a surface roughness of <6 Å for λ/4 thickness at 1 μm. The Y2O3 films are transparent with extremely low absorption loss at 1 μm and laser damage is in the range 10 J/cm2 when tested at a wavelength of 1.03 μm and pulse duration of 375 ps.

Femtosecond to nanosecond laser damage in dielectric materials

We present a consistent model supported by experimental data of damage of dielectric films by femtosecond to nanosecond pulses. Special emphasis is given to the role of defects and transient processes in the material. New imaging and diagnostic techniques are discussed to characterize the film performance.

Scandium Oxide Thin Films Deposited by Dual Ion Beam Sputtering for High-Power Laser Applications

Scandium oxide films were deposited using reactive dual ion beam puttering. At 1 micron, the refractive index of the films is 1.95 and the absorption loss is 18.5 ppm. X-ray photoelectron spectroscopy showed oxygen defects.

Optimization of scandia thin films for high power laser coating applications

We discuss the physical and optical properties of Sc2O3 single layers deposited by the dual ion beam sputtering technique at oxygen partial pressures ranging from 1.7×10-5 to 5.1×10-5 Torr. The films are amorphous with crystallite size ~10 nm and have surface roughness RMS values of 1.2±0.3 nm. The refractive index at 1 μm is 1.95. Absorption loss is shown to be sensitive to the oxygen partial pressure during growth. Multiple-pulse damage experiments suggest that the scandia film deposited at the higher oxygen partial pressure accumulates laser-induced trap defects more slowly than the scandia film deposited in a lower oxygen partial pressure atmosphere.

Influence of Process Conditions on the Optical Properties HfO 2 /SiO 2 Thin Films for High Power Laser Coatings

The influence of process conditions on loss, refractive index, and laser induced damage threshold of HfO2/SiO2thin films grown by ion beam assisted sputtering is investigated to realize films with losses less than 20 ppm.

Influence of oxygen pressure variations on the optical properties of ion beam sputtered metal oxide coatings

Small variations of oxygen partial pressure during the ion beam sputtering of metal oxides strongly influence the optical properties, causing an increase in the absorption loss and a decrease in laser damage fluence.