162,183 research outputs found
Micro patterning of fused silica by laser ablation mediated by solid coating absorption
No full textPrecise patterning by laser ablation requires sufficient absorption. For weak absorbers like fused silica indirect methods using external absorbers have been developed. A novel approach using a solid SiO absorber coating is described. Irradiation by an ArF excimer laser ( wavelength 193 nm) is leading to ablation of the coating and, at sufficiently high fluence, of the fused silica substrate. The remaining coating in the unexposed areas is removed afterwards by large area irradiation. The fluence threshold for substrate ablation using a 28 nmthick absorber layer is about 1.1 J/cm(2). Single pulse ablation rates of up to 800 nm and a surface roughness of R-a < 5 nm are obtained. High resolution grating patterns with 400 nm period and a modulation depth of 80 nm are possible. The process can be described as controlled plasma mediated ablation
High resolution patterning of sapphire by F2-laser ablation
No full textThe ablation behavior of single crystalline sapphire with nanosecond laser pulses at 157 nm wavelength is investigated. Ablation rates of about 10 to 100 nm/pulse are obtained at fluences ranging from 1 to 9 J/cm(2). At moderate fluences, incubation behavior is observed, i.e. ablation starts after material modification by a number of laser pulses. The ablation can be utilized to fabricate sapphire micro-optics. The capability of creating lenses or gratings on the tip of sapphire fibers is demonstrated. Multilevel diffractive optical elements and high resolution gratings with 1 mu m period are fabricated on planar sapphire substrates.German Ministry of Economics and Technology [16IN0505
Ablation of microstructures applying diffractive elements and UV femtosecond laser pulses
No full textA new method for simple and economic fabrication of diffractive optical elements (DOEs) with three and four phase levels, by UV nanosecond (ns) laser ablation is presented. The technique is based on the combination of two sequentially generated complementary 2-level phase elements. During the fabrication, complete ablative removal of a highly absorbing silicon suboxide layer by pixelated backside illumination ensures the necessary high precision and optical quality. Full functionality of the new DOEs is demonstrated by fabricating micro-structures using UV femtosecond pulses.TEKES; TEKES, the Finnish Agency for Technology and Innovatio
Laser patterning of SiOx-layers for the fabrication of UV diffractive phase elements
No full textDiffractive phase elements (DPE), consisting of a patterned UV-transparent layer on a UV-transparent substrate, were fabricated by three steps. A UV-absorbing SiOx-coating (x < 2) with a thickness matching to the required phase delay was deposited on a fused silica substrate. The coating was removed on a pixel array corresponding to a calculated two-dimensional quantized phase function (DPE-design). By a thermal annealing process the SiOx-coating was oxidised to UV-transparent SiO2, resulting in a UV-grade surface relief element. (c) 2005 Elsevier B.V. All rights reserved
Patterned laser annealing of silicon oxide films
No full textUV-absorbing silicon monoxide (SiO (x) , xa parts per thousand 1) thin films on fused silica substrates are irradiated by an ArF excimer laser (wavelength 193 nm) in the sub-ablation threshold regime. Multi-pulse irradiation of films with similar to 200-nm thickness at a fluence of about 100 mJ/cm(2) leads to a significant increase of the UV transmission, indicating the oxidation of SiO (x) to SiO(2). The quality of the obtained films after this laser annealing process depends on the oxygen content of the environment. Irradiation in air at atmospheric pressure leads to the formation of sub-micron-sized oxide particles on top of the film. Structured illumination is applied either to form areas of the film with changed transmission and refractive index, or for the formation of regular particle patterns with sub-micron periods. These processes can be utilized for the fabrication of phase masks or for various types of surface functionalization.German Ministry of Economics and Technology [16IN0505
Deterministic sub-micron 2D grating structures on steel by UV-fs-laser interference patterning
No full textLarge area linear and crossed grating structures on steel surfaces are obtained by UV-femtosecond-laser ablation at 248 nm. High resolution on large areas is secured using a beam delivery system based on a two-grating interferometer. Thus, deterministic gratings with periods down to 330 nm and modulation depths of more than 100 nm are fabricated on tool steel and stainless steel. Areas of up to mm can be processed without stitching errors
Laser Based Rapid Fabrication of SiO2-phase Masks for Efficient UV-laser Micromachining
No full textThe laser based fabrication of surface relief SiO2 phase masks is demonstrated: First, a UV-absorbing coating of silicon monoxide (SiO, thickness 150-300 nm) is deposited on a fused silica substrate. Second, the SiO-coating is patterned by excimer laser ablation (248 nm or 193 nm) at fluences of 0.2 to 0.5 J/cm(2) to form the desired phase structure. Third, the SiO-material is oxidized to UV-transparent silicon dioxide (SiO2). Applications of these phase masks in combination with suitable imaging optics for efficient laser micro machining are demonstrated.BMWi of Germany [16IN0351
Submicron surface patterning by laser ablation with short UV pulses using a proximity phase mask setup
No full textA new approach for the generation of large-area periodic surface structures on different materials, like polymers and semiconductors, by direct laser ablation is presented. The surfaces were illuminated with the interference pattern emerging in close proximity behind a laser irradiated phase mask. In the experiments, nanosecond and picosecond laser pulses at 248 nm were applied. To prevent contamination or damage of the phase mask caused by the ablated material, the mask is protected by a thin water film or a thin quartz plate. In addition we present a technique to eliminate a lateral variation of the generated structures due to insufficient alignment precision of the workpiece.Ministry for Science and Culture of Lower Saxony [13-76102-11-1-15
Laser Based Rapid Fabrication of SiO2-phase Masks for Efficient UV-laser Micromachining
No full textThe laser based fabrication of surface relief SiO2 phase masks is demonstrated: First, a UV-absorbing coating of silicon monoxide (SiO, thickness 150-300 nm) is deposited on a fused silica substrate. Second, the SiO-coating is patterned by excimer laser ablation (248 nm or 193 nm) at fluences of 0.2 to 0.5 J/cm(2) to form the desired phase structure. Third, the SiO-material is oxidized to UV-transparent silicon dioxide (SiO2). Applications of these phase masks in combination with suitable imaging optics for efficient laser micro machining are demonstrated.BMWi of Germany [16IN0351
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
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