Using an in-house developed micro scanner three-dimensional micro components and micro fluidic devices in fused silica are realized using the ISLE process (in-volume selective laser-induced etching). With the micro scanner system the potential of high average power femtosecond lasers (P > 100 W) is exploited by the fabrication of components with micrometer precision at scan speeds of several meters per second. A commercially available galvanometer scanner is combined with an acousto-optical and/or electro-optical beam deflector and translation stages. For focusing laser radiation high numerical aperture microscope objectives (NA > 0.3) are used generating a focal volume of a few cubic micrometers. After laser exposure the materials are chemically wet etched in aqueous solution. The laser-exposed material is etched whereas the unexposed material remains nearly unchanged. Using the described technique called ISLE the fabrication of three-dimensional micro components, micro holes, cuts and channels is possible with high average power femtosecond lasers resulting in a reduced processing time for exposure. By developing the high speed micro scanner up-scaling of the ISLE process is demonstrated. The fabricated components made out of glass can be applied in various markets like biological and medical diagnostics as well as in micro mechanics.

Single tracks and pairs of tracks are written in the volume of Pr-doped LiYF4-crystals using tightly focused femtosecond laser radiation (λ=1045 nm, τ p=400–500 fs, f=0.1–1 MHz). Waveguiding between the tracks is demonstrated and optimized by varying the distance between the tracks and the laser writing conditions. The stress-induced guiding mechanism is explained based on TEM, interference microscopy, near-field and far-field measurements. It is shown that the single-crystalline material is getting poly-crystalline under femtosecond laser irradiation. By measuring the lifetime of the 3P1→3H5 transition and the emission spectrum at excitation with λ=444 nm, no influence on these properties of the guided light is observed. This possibly enables the realization of a channel waveguide laser in the visible spectral range.

By focusing fs-laser radiation in the volume of a transparent material the refractive index can be changed locally, leading to 3-dimensional waveguiding structures. Waveguides are written in phosphate glass (IOG from Schott) at a depth of 100 μm below the surface. The pulse energy and the scan velocity are varied. For the first time the optical path difference caused by the waveguides and therefore the refractive index distribution of the waveguides and their cross sections are determined using interference microscopy. The optical path difference measured in the written structures and their cross sections is analyzed by a phase-shift algorithm. Thus, the refractive index distribution both along a line perpendicular to the waveguide and in the plane of a cross section is determined. The results are visualized as 2-dimensional graphics. Several regions of opposite sign of the refractive index change are observed in the cross sections of waveguides generated by femtosecond laser pulses. The number and the size of these regions are increasing with increasing pulse energy and decreasing scan velocity.

Refractive index modifications are fabricated in the volume of rare-earth-doped glass materials namely Er-and Pr-doped ZBLAN (a fluoride glass consisting of ZrF4, BaF2, LaF3, AlF3, NaF), an Er-doped nano-crystalline glass-ceramic and Yb- and Er-doped phosphate glass IOG. Femtosecond laser radiation (tau=500fs, lambda=1045nm, f=0.1-5MHz) from an Yb-fiber laser is focused with a microscope objective in the volume of the glass materials and scanned below the surface with different scan velocities and pulse energies. Non-linear absorption processes like multiphoton- and avalanche absorption lead to localized density changes and the formation of color centers. The refractive index change is localized to the focal volume of the laser radiation and therefore, a precise control of the modified volume is possible. The width of the written structures is analyzed by transmission light microscopy and additionally with the quantitative phase microscopy (QPm) software to determine the refractive index distribution perpendicular to a waveguide. Structures larger than 50 mu m in width are generated at high repetition rates due to heat accumulation effects. In addition, the fabricated waveguides are investigated by far-field measurements of the guided light to determine their numerical apertures. Using interference microscopy the refractive index distribution of waveguide cross-sections in phosphate glass IOG is determined. Several regions with an alternating refractive index change are observed whose size depend on the applied pulse energies and scan velocities.

Micro-channels in fused silica and waveguides in laser active glass materials are fabricated with fs-laser pulses. The use of a high repetition rate laser and a fast scanning system potentially allow the fabrication of laser sources and micro-mechanical components with high speed.

Using fs-laser direct writing periodical surface nanostructures are fabricated on the surface of dielectric materials. By using high repetition rate fs-laser radiation with a wavelength of 1045 nm periodical nanostructures with periods of 200-350 nm are obtained on dielectrics. In this paper the pump-probe technique is used for time-resolved investigations of the spectral reflectivity and transmittivity during and up to 1 ns after the fs-laser pulse. From this measurements the transient electron density in the conduction band and the transient dielectric function are calculated and used to extend the classical ripples theory with the transiently modified dielectric function. The periods of the surface nanostructures are compared to the calculations and discussed.

Since green laser diodes are still not commercially available, alternative technologies like frequency doubling have to be used for compact green laser sources. The goal of this work is to develop diode pumped green erbium-doped glass up-conversion waveguide lasers, instead. Planar fluoride glass waveguides are fabricated using a spin-coating technology. Until now, planar fluoride glass film waveguides with thicknesses are achieved down to 30 mum. The waveguides were doped with up to 3 mol% erbium. Scattering losses of 0.2 dB/cm at 975 nm and strong green emission at 520 - 550 nm is observed in erbium-doped waveguides 50 mum in thickness.

Thin films made by PLD from Er:ZBLAN and Nd:Gd3Ga5O12 are micro machined to form optical wave guiding structures using Ti:sapphire and Yb:glass fiber laser radiation. For the manufacturing of the ridge waveguides grooves are structured by ablation using femtosecond laser radiation. The fluence, the scanning velocity, the repetition rate, and the orientation of the polarization with respect to the scanning direction are varied. The resulting structures are characterized using optical microscopy and scanning electron microscopy. Damping and absorption coefficients of the waveguides are determined by observing the light scattered from the waveguides due to droplets in the thin films and the surface roughness of the structured edges. To discriminate between damping due to droplets and the structured edges, damping measurements in the non-structured films and the structured waveguides are performed. Ridge waveguides with non-resonant damping losses smaller than 3 dB/cm are achieved. Due to the high repetition rate of the Yb:glass fiber laser, the manufacturing time for one waveguide has been decreased by a factor of more than 100 compared to earlier results achieved with the Ti:sapphire laser.

Sub wavelength ripples (spacing < lambda/4) perpendicular to the polarisation of the laser radiation are obtained by scanning a tightly focused beam (-1 mu m) of femtosecond laser radiation from a Ti:Sapphire laser (tau=100fs, lambda=800nm & 400nm, f=1kHz) and from a Yb:glass fiber laser (tau=400fs, lambda=1045nm, f=0.1-5MHz) over the surface of various materials like amorphous Nd:Gd3Ga5O12 films 1 mu m in thickness on YAG substrates, diamond, polytetrafluoroethylene, LiF, MgF2, ZBLAN, Al2O3, LiNbO3, SiO2, Si, Cu and Au. The ripple patterns extend coherently over many overlapping laser pulses and scanning tracks.Investigated are the dependence of the ripple spacing Lambda on the material, the lateral distance of the laser pulses, the N.A. of the focussing optics, the repetition rate and the applied wavelength. The ripples are characterised using electron microscopy. Some possible models for the origin of the ripple growth are discussed. New results concerning the scaling of the production process using a high repetition rate laser and a fast translation stage are demonstrated. The cross-sections of the ripples are investigated using electron microscopy. A very large aspect ration of similar to 10 is observed for the periodical nanostructures in fused silica.Using in-volume selective laser etching (ISLE) of sapphire results in deep hollow nanoplanes similar to 200 nm in width and up to 1 mm in length. Microchannels have been produced using in-volume selective laser etching with a scanning speed of 1 mm/s.

Sub wavelength ripples (spacing < lambda/4) perpendicular to the polarisation of the laser radiation are obtained by scanning a tightly focused beam (similar to 1 mu m) of femtosecond laser radiation from a Ti:Sapphire laser (tau=100fs, lambda=800nm & 400nm, f=1kHz) and from a Yb:glass fiber laser (tau=400fs, lambda=1045nm, f=0.1-5MHz) over the Surface of various materials like amorphous Nd:Gd3Ga5O12 films 1 mu m in thickness oil YAG substrates, diamond, polytetrafluoroethylene, LiF, MgF2, ZBLAN, Al2O3, LiNbO3, SiO2, Si, Cu and An. The ripple patterns extend coherently over many overlapping laser pulses and scanning tracks. Investigated are the dependence of the ripple spacing A on the material, the lateral distance of the laser pulses, the N.A. of the focussing optics, the repetition rate and the applied wavelength. The ripples are characterised using electron microscopy. Some possible models for the origin of the ripple growth are discussed and conditions under which these phenomena occur are contained. New results concerning the scaling of the production process using a high repetition rate laser and a fast translation stage are demonstrated. Potential applications are presented and consequences for precise nano- and microstructuring using ultra short pulsed lasers are discussed.

Ridge waveguides are manufactured using laser radiation for the deposition of thin films and the micro structuring of the wave guiding structures.The optical properties of erbium, and praseodymium doped ZBLAN thin films and waveguides are investigated in view of the manufacturing of green integrated waveguide lasers.

Waveguide lasers are manufactured using laser radiation for the deposition of thin films and the micro structuring of the wave guiding structures. For the first time laser activity in fs-laser structured amorphous waveguides was achieved.

Ripples (spacing <λ/4) are obtained by scanning femtosecond laser radiation (τ=100fs & 400fs, λ=800nm & 1045nm) over the surface of various materials. The ripple patterns extend coherently over many overlapping laser pulses and scanning tracks.

Sub-wavelength (1/4*lambda-3/4*lambda) laser induced periodic surface structures are generated by irradiation of either bulk fused silica and silicon or Er:BaTiO3 thin films by scanning a tightly focused beam (phi=1mum) of femtosecond laser radiation (lambda=800nm, t(p)= 100fs) on the surface. The ripple pattern extends coherently over many overlapping laser pulses parallel and perpendicular to the polarisation of the laser radiation. The dependence of the ripple spacing on the spacing of successive pulses, the direction of polarisation and the properties of the material is investigated. The evolution of the ripples is investigated by applying pulse bursts with 1-20 pulses. The development conditions of the structures are specified and possible mechanisms of ripple growth are discussed.

Laser radiation is used for the deposition of dielectric erbium doped BaTiO3 thin films for photonic applications. Pulsed laser deposition with KrF excimer laser radiation (wavelength 248 nm, pulse duration 20 ns) is used to grow dense, transparent, amorphous, poly-crystalline and single crystalline erbium doped BaTiO3 thin films. Visible emission due to up-conversion luminescence (wavelength 528 nm and 548 nm) under excitation with diode laser radiation at a wavelength of 970–985 nm is investigated as a function of the erbium concentration of 1–20 mol % and structural film properties.

The deposition of BaTiO3 thin films by pulsed excimer laser radiation (248 nm) on Pt/Ti/Si(111) and Pt/Ti/Si(100) substrates is investigated as a function of the processing variables laser fluence, processing gas pressure and target-to-substrate distance. The influence of the kinetic energy of the film-forming particles on the crystalline structure, defects and orientation and on the resulting electrical properties of the films is investigated. X-ray diffraction measurements and polarisation-dependent micro Raman measurements reveal a c-axis orientation normal to the substrate surface, in the case of high particle energy (> 50 eV), while at low kinetic energies (<30 eV) a [111]pc or [110]pc orientation is preferred. The ferroelectricity and the dielectric constant of the films, determined by impedance measurements, decrease with increasing kinetic energy of the film-forming particles from εr=1000–2200 to εr=200–700. This decrease correlates with the change of the orientation and with an increasing lattice constant of the films, indicating that particles with high kinetic energies produce crystal defects and stress in the growing film.

Structuring of poly ether ether ketone (PEEK) by 193nm ArF excimer laser radiation has been investigated. Experiments were carried out in different atmospheres (air, vacuum, Ar, O2) in order to study its influence on the quality of the structures and the formation of the debris. Repetition rate makes little effect on the ablation rate and roughness of the structure in presence of any kind of atmosphere, indicating for the structuring of PEEK by ArF laser radiation a large window of processing. The roughness at the bottom of the structures and the morphology of the side walls are strongly affected by the properties of the atmosphere. The smallest roughness is achieved at 0.6J/cm2 for all kinds of processing gases. Debris around the structures can be diminished by structuring in vacuum. Plasma expansion speed has been measured by using high speed photography.

The dynamics of the laser induced plasma during pulsed laser deposition of BaTiO3 thin films is studied theoretically and experimentally and related to the resulting film properties. The expansion of the laser induced plasma is modelled taking inelastic collisions between ablated particles and processing gas particles into account. The predictions of the model are in agreement with data from high speed photography of the plasma emission. Pulsed laser deposition with KrF excimer laser radiation (wavelength 248nm, pulse duration 20 ns) is used to grow dense, transparent, amorphous, poly-crystalline and single crystalline erbium doped BaTiO3 thin films for photonic applications. Visible emission due to up-conversion luminescence (wavelength 528 nm and 548 nm) under excitation with diode laser radiation at a wavelength of 970-985 nm is investigated as a function of the erbium concentration of 1 - 46 mol % and structural film properties. The dielectric films are micro machined to form optical wave guiding structures using Ti:sapphire laser radiation (wavelength 810 nm, pulse duration 63 - 150 fs) by scanning the focussed laser beam relatively to the sample.

Using a high dielectric material as substitute for SiOxNy in dielectric film capacitors of dynamic memories (DRAM) allows a significantly higher integration density and a reduction of the die size, even with planar capacitors. BaTiO3 is such a material. A dielectric constant of epsilon(r) > 1000 has been achieved in thin films, made by pulsed laser deposition (PLD). For applications in microelectronic memories it is necessary to produce crystalline, defect-free and oriented BaTiO3 thin films at substrate temperatures, T-S < 450 degreesC.Sintered targets of BaTiO3 are ablated by KrF excimer laser radiation. The processing gas atmosphere consists of O-2 at pressures of 0.1-50 Pa. The substrate is resitively heated to 360-440 degreesC and annealed after or during PLD on Pt/Ti/Si multilayer substrates using KrF excimer laser radiation with fluences up to 120 mJ/cm(2).The temperature distribution in the BaTiO3/Pt/Ti/Si multilayers during laser annealing is dynamically modelled and related to the resulting crystal quality and the dielectric properties of the films. With PLD a minimum substrate temperature of 500 degreesC is necessary to deposit crystalline BaTiO3 films. Using in situ laser crystallisation crystalline BaTiO3 films can be deposited at substrate temperatures of T-S = 360-440 degreesC showing a dielectric constant of up to epsilon(r) = 1200.The ferroelectric and dielectric properties of the films are determined by C-V and P-V impedance measurements and correlated to the chemical and structural properties, as determined by X-ray photoemission spectroscopy, X-ray diffraction, micro Raman spectroscopy and scanning electron microscopy. (C) 2002 Elsevier Science B.V All rights reserved.

The deposition of different hard ceramics coatings as Al2O3, ZrO2, c-BN and DLC thin films by pulsed laser deposition (PLD) has been of increasing interest as alternative process compared to the latest progress in CVD and PVD deposition. For instance, in pulsed laser deposition, the properties of the resulting thin films are influenced by the composition, ionization state, density, kinetic and excitation energies of the particles of the vapor/plasma. In order to deposit hard ceramics with different properties and applications, various substrates as Pt/Ti/Si multilayer, glass (fused silica), steel, polymethylmethacrylate (PMMA), polycarbonate (PC), Si(100) and Si(111) are used. These thin films are deposited either by excimer laser radiation (lambda = 248nm) or by CO2 laser radiation (lambda = 10,6 mum). To characterize the structural, optical and mechanical properties of the hard ceramics thin films, different techniques as Raman spectroscopy, ellipsometry, FTIR-spectroscopy and nanoindentation are used.