In this publication we present a novel setup for the Optical Trap Assisted Nanopatterning (OTAN) technology. The setup allows process parallelization and thus higher throughput in this inventive and flexible direct-nanopatterning technology. We have determined the stiffness of the optical traps and compared the obtained result with the single beam OTAN parameters. Furthermore we estimate the increase in throughput for the parallelized approach in comparison to the conventional system.

Indium tin oxide (ITO) is one of the few materials that combine optical transparency in the visible light spectrum with high electrical conductivity. These properties provide functionality in many optoelectronic applications but their application to certain fields is limited by the need to achieve advanced mechanical properties, hence requiring micromechanical characterization methods. In this paper, ITO coatings of 94–325nm thickness are produced from spin-coating of nanoparticle ink followed by consolidation by nanosecond UV laser irradiation in ambient air. These ITO layers are investigated by nanoindentation and scratch testing, which provide measurements of their hardness, Young's modulus and scratch resistance. This allows understanding the effect of the process parameters on the mechanical properties of the layers. It is concluded that a laser fluence of 59mJ/cm2 provides an effective mechanical consolidation of ITO particles up to 150nm thickness.

Layers of indium-tin-oxide (ITO) nanoparticles were deposited on the polymer substrates polypropylene and polyimide in ambient air. To decrease the electrical resistance of the deposited nanoparticle ITO layer precipitated organic compounds of the nanoink have to be removed. For temperature-resistant substrates a baking step is suitable for the removal of organic agents utilizing a hotplate. However, a hotplate baking is not suitable for organic substrates. In order to avoid thermal damage the polymer substrate laser based removal strategies were investigated utilizing ultraviolet and infrared laser irradiation. To further optimize the electrical conductivity of the ITO nanoparticle layer a final laser consolidation step is essential utilizing ultraviolet laser light provided by a KrF excimer laser.

Fabrication of phase only holograms via spatially selective ablation of an ITO nanoparticulate layer coated on an optical quality transparent substrate appears to be very attractive due to the simplicity and flexibility of this approach. A pre-calculated binary pattern can be directly written on such a layer in order to produce a desired intensity distribution in the focal plane of a focusing lens. In this contribution we analyze the performance of the fabricated holograms and their suitability for high power beam shaping as well as propose a way to improve the diffraction efficiency of such structures by transitioning from a single to multi-layer holograms.

High-power ultrashort pulsed lasers with average powers exceeding 100 W are commercially available. Yet, the successful transfer of such lasers into application, microstructuring in particular, lacks appropriate tools. The most promising strategies today are high-speed beam scanning or parallelization in terms of beam shaping or multi-spot generation. A combination of both strategies into one device would be the most promising tool to reach much higher processing efficiencies compared to date. We will present the first sub-steps we are undertaking to realize such devices, utilizing the acoustooptic effect as well as liquid crystal based modulators and phase holograms. First results include the rapid manufacturing of phase holograms and high-speed beam scanning and shaping using acoustooptical deflectors - reaching beam shape switching times of 1 mu s.

Phase holograms offer great potential e.g. for laser beam shaping and imaging applications. However, the generation of these structures typically requires multi-step processes which tend to be time-consuming and expensive, especially if high-quality structures are required. In this work we demonstrate a flexible and inexpensive method which allows for the production of binary phase-only holograms by laser ablation of ITO nanoparticle layers. Since these layers are ablated free of residues, accurately defined phase shifts can be achieved. While arbitrarily shaped structures can be generated, the ITO layer thickness can be adjusted in order to freely tune the phase shift for the desired wavelength. In the diffraction patterns generated by the holograms we observed an excellent zero order suppression.

Indium tin oxide (ITO) is one of the few materials, which combines optical transparency in the wavelength range of visible light and electrical conductivity. It offers a wide range of applications in the field of optoelectronic devices such as solar cells or displays. To the present day, ITO is commonly deposited in a vacuum environment. Deposition under vacuum atmosphere is a cost-intensive process and not compatible with modern manufacturing techniques, like roll-to-roll processing. To overcome this limitation we propose the generation of ITO layers by deposition of ITO nanoparticles under atmospheric conditions.For the generation of functional devices structured layers are required. The exact damage threshold of nanoparticulate ITO layers is essential to minimize influence of the structuring process on the substrate.In our measurements we used three different substrates, spin coated layers, annealed layers and consolidated layers.

We perform structural characterisation of direct laser write (DLW) waveguides. Quantitative phase microscopy, based on solution of the transfer of intensity equation, is used to measure the cumulative refractive index change through a waveguide perpendicular to its axis. Results are compared with interferometry, cross-sectional measurements using third harmonic microscopy, and analysis of the near-field image of the mode propagating in the waveguide. We show that in many situations, notably in the presence of depth dependent spherical aberrations, the cross-section for DLW waveguides may not be assumed symmetric about the waveguide axis. This is particularly important when fabricating at depths greater than 2 mm in fused silica. Therefore additional measurements are required to fully characterise the refractive index profile.

The spherical aberration generated when focusing from air into another medium limits the depth at which ultrafast laser machining can be accurately maintained. We investigate how the depth range may be extended using aberration correction via a liquid crystal spatial light modulator (SLM), in both single point and parallel multi-point fabrication in fused silica. At a moderate numerical aperture (NA = 0.5), high fidelity fabrication with a significant level of parallelisation is demonstrated at the working distance of the objective lens, corresponding to a depth in the glass of 2.4 mm. With a higher numerical aperture (NA = 0.75) objective lens, single point fabrication is demonstrated to a depth of 1 mm utilising the full NA, and deeper with reduced NA, while maintaining high repeatability. We present a complementary theoretical model that enables prediction of the effectiveness of SLM based correction for different aberration magnitudes.

Layers of ZnO nanoparticles with thicknesses of about 40 nm were prepared on silicon substrates. The layers were irradiated by single pulses of a 248 nm excimer laser, which proofed suitable for consolidation and significant densification of the particle layers under ambient conditions. Experiments as well as simulations have confirmed that the application of a SiO2 particle layer between the substrate and the ZnO particle layer can be used to hamper heat transfer towards the substrate. Thus the ZnO layer can be thermally insulated from the substrate while heating the ZnO up to its extremely high melting point. Consequently, such a layer stack could enable the application of consolidated particle layers on temperature-sensitive carrier substrates such as polymer foils which are to be used in low-cost mass production of devices like displays or solar cells.

Indium tin oxide (ITO) is one of the few materials available that display a high transparency in the visible wavelength region and at the same time can conduct electrical currents. Thus it is widespread in many optoelectronic applications such as displays or solar cells. Layers of this material are commonly deposited by vacuum deposition methods which are not compatible with inexpensive production methods such as roll-to-roll processing or printed electronics in general. In this work, we demonstrate the generation of arbitrarily shaped ITO layers by laser induced forward transfer of ITO nanoparticles. The transferred particle ink volumes range in the sub picoliter regime. Feature sizes as small as 20 μm are produced without any outward flow or “coffee-stain” effects. Furthermore, the feasibility of excimer laser consolidation of these nanoparticulate layers in ambient air for the generation of dense ITO films is shown. Conductivities of over 4000 Ω−1 m−1 were achieved. The presented methods are a promising alternative for the generation of transparent conducting layers for the inexpensive production of optoelectronics.

The functional and geometrical requirements to electronic, optoelectronic and mechatronic devices have significantly increased during the last years. Within the scope of the development and the fabrication of such components a very important aspect is the fast and flexible generation of conductive circuits respectively structures on work-pieces of various dimensions and materials. The presented work gives an overview about three promising laser-based approaches to generate microscopic and macroscopic circuits as well as conductive layers with a thickness in the order of a few hundred nanometers. In addition to processes for the fabrication of conductive structures laser-based soldering of piezo-composites is investigated.

Nanoparticles of transparent conducting oxides, such as indium tin oxide, can be used in printing techniques to generate functional layers for various optoelectronic devices. Since these deposition methods do not create fully consolidated films, the optical properties of such layers are expected to be notably different from those of the bulk material and should be characterized on their own. In this work we present a way to measure the effective refractive index of a particulate ITO layer by refraction of light. The obtained data points are used to identify an accurate layer model for spectroscopic ellipsometry. In this way the complex refractive index of the particle layer is determined in a wide spectral range from ultra violet to near infrared.

Layers of ZnO nanoparticles with thicknesses of about 40 nm were prepared on Si substrates. It was shown that UV laser irradiation is suitable for consolidation and significant densification of the ZnO particle layers under ambient conditions. Both experiments and simulations show that an underlying SiO2 particle layer has a beneficial effect in inhibiting heat transfer towards the substrate and thus enables the application of temperature-sensitive carrier substrates like polymer foils despite the extremely high melting temperature of ZnO.

Indium tin oxide (ITO) nanoparticle films for applications in printable electronics were prepared by dip-coating. The dispersion conditions (bead size, stabilizer concentration) strongly affect the particle size of the ITO suspensions and consequently determine the surface morphology of the ITO films. Deposition from ethanolic ITO suspensions with an extremely small particle size of 17nm to 21nm led to the formation of extremely smooth and spike-free ITO films with a typical root mean square surface roughness of 4.5nm±0.2nm and a high optical transparency above 95%. The effect of annealing with forming gas and CO2 laser treatment on the electrical properties of the ITO films was investigated. Annealing with forming gas and CO2 laser treatment led to a temporary increase in the electrical conductivity of the ITO films by up to a factor of 10 and 6, respectively. Specific conductivities of up to 196Scm−1 were obtained for our ITO nanoparticle films under optimized conditions.

Layers of ITO nanoparticles were deposited on soda-lime substrates by spincoating in order to produce conductive transparent electrodes. Different lasers in the UV and mid infrared wavelength region were used for post deposition treatment of the layers to remove stabilizing agents contained in the layers to enhance particle-particle contact and significantly increase conductivities. Irradiation with lasers in the infrared region showed good results in terms of stabilizer removal without undesired oxidizing effects to the particle layer. Conductivities of up to 120 S/cm were achieved, which is comparable to layer treatment by annealing and a subsequent chemical reducing step. DOI:10.2961/jlmn.2011.03.0003