This PDF file contains the front matter associated with SPIE Proceedings Volume 7585, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Now that high brightness laser sources featuring high output power are commercially available, extremely small focal diameters and high power densities permit laser welding with a high aspect ratio at low heat input. With regard to an increase in productivity this implies a deeper weld depth at a higher feed rate and hence at a shorter processing time. In this research, a modular optical system generates focal diameters from 195 μm down to 15 μm for the purpose of identifying the prospects and limitations of the application of high brightness beam sources in laser welding. Metallographical analysis and observation using a high speed camera give information about the weld seam geometry and weld pool dynamics. Thus, the influence of minimizing focal diameters on process stability is evaluated: From the correlation of longitudinal cross-sections and high speed camera observation, an interrelationship between spiking and keyhole breakdown results. In dependence of the particular spot size and the beam quality of the laser source a new processing range arises. These observations are traced back to theoretical beam properties and a fundamental thesis about the applicability of a high brightness laser is derived. Eventually it shows that a small beam diameter is most advantageous for micro application.

With the help of a CO₂-laser (λ = 10.64 μm) Silicon carbide (Trade name: Ekasic-F, Comp: ESK Ceramics) has been brazed to commercial steel (C45E, Matnr. 1.1191) using SnAgTi-filler alloys. The braze pellets were dry pressed based on commercially available powders and polished to a thickness of 300 μm. The SnAgTi-fractions were varied with the objective of improving the compound strength. Furthermore, tungsten reinforced SnAgTi-fillers were examined with regard to the shear strength of the ceramic/steel joints. Polished microsections of SnAgTi-pellets were investigated before brazing in order to evaluate the particle distribution and to detect potential porosities using optical microscopy. The brazing temperature and the influence of the reinforcing particles on the active braze filler were determined by measurements with a differential scanning calorimeter (DSC). After brazing. the ceramic-steel joints were characterized by scanning electron micrographs and EDX-analysis. Finally the mechanical strength of the braze-joints was determined by shear tests.

In recent years various techniques have been developed for the manufacture of microsystems and other miniature optoelectronic devices. One aspect where there remains significant room for improvement is the packaging process. Standard packaging techniques involve heating whole devices to high temperatures, in some cases combined with strong electric fields, preventing the use of temperature-sensitive materials within the package and generating problems in manufacturing processes where a number of thermal process steps are carried out sequentially, when a later heating step can cause parts joined earlier to disassemble. Here we describe the successful application of laser-based joining for the packaging of such devices.

Laser beam soldering is a packaging technology alternative to polymeric adhesive bonding in terms of stability and functionality. Nevertheless, when packaging especially micro optical and MOEMS systems this technology has to fulfil stringent requirements for accuracy in the micron and submicron range. Investigating the assembly of several laser optical systems it has been shown that micron accuracy and submicron reproducibility can be reached when using design-of-experiment optimized solder processes that are based on applying liquid solder drops ("Solder Bumping") onto wettable metalized joining surfaces of optical components. The soldered assemblies were subject to thermal cycles and vibration/ shock test also.

This work investigates fabrication of functional conductive carbon paste onto a plastic substrate using a laser. The method allows simultaneous sintering, patterning, and functionalization of the carbon paste. Experiments are carried out to optimize the laser processing parameters. It is shown that sheet resistance values obtained by laser sintering are close to the one specified by the manufacturer using conventional sintering method. Additionally, a heat transfer analysis using numerical methods is conducted to understand the relationship between the temperature during sintering and the sheet resistance values of sintered carbon wires. The process developed in this work has the potential of producing carbon-based electronic components on low cost plastic substrates.

We describe resonant infrared pulsed laser deposition (RIR-PLD) of cyclic olefin copolymer, a barrier and protective layer; for comparison, we describe RIR-PLD of polystyrene and poly(ethylene dioxythiophene) about which we already have significant knowledge. Film deposition based on resonant infrared laser ablation is a low-temperature process leading to evaporation and deposition of intact molecules. In this paper, we focus on deposition of this model barrier and protective material that is potentially useful in the fabrication of organic light emitting diodes. The films were characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. We also compared the properties of films deposited by a free electron laser and a picosecond optical parametric oscillator.

Growing carbon nanotubes (CNTs) of different alignments, including surface-bounded and vertically aligned arrays, on metallic electrodes was achieved by applying electric voltages of different polarities on metallic electrodes during the laser-assisted chemical vapor deposition process. Surface-bounded CNTs were found to crawl out from the positively charged electrodes. In contrary, vertically aligned CNTs dominated the negatively charged electrodes. The alignment control was ascribed to the movement of catalyst-nanoparticles (NPs) under the influence of external electric field. The surface-bounded CNTs were ascribed to the repulsive forces between the catalyst NPs and the anodes. The vertically aligned CNTs were ascribed to the joint interactions of catalyst-cathode interactions and tube-tube interactions. This investigation suggests a convenient approach to control the alignment of CNT arrays for applications in different fields.

CO₂ laser resonant excitations of precursor molecules were applied in combustion flame synthesis of diamond films. The combustion flame was produced from a mixture of ethylene (C₂H₄), acetylene (C₂H₂) and oxygen (O₂). A wavelength-tunable CO₂ laser with wavelength range from 9.2 to 10.9 μm was used for wavelength-matched excitation of the ethylene molecules. By irradiating the flame using CO₂ laser at 10.532 μm, the ethylene molecules were resonantly excited through the CH₂ wagging vibrational mode (ν₇, 949.3 cm^-1). Irradiation of the flame using the common CO₂ laser wavelength at 10.591 μm was also carried out for comparison. It was found that diamond synthesis was more obviously enhanced by the CO₂ laser resonant excitation at 10.532 μm as compared to that at 10.591 μm. Firstly, the flame was shortened by 50%, indicating a promoted reaction in the process. Secondly, the diamond grain sizes as well as the diamond film thicknesses were increased by 200~300% and 160% respectively, indicating a higher growth rate of diamond films. Finally, Raman spectra of the diamond sample showed a sharp diamond peak at 1334 cm^-1 and a suppressed G-band, indicating higher diamond quality.

Optical emission spectroscopy (OES) measurements were carried out to study premixed C₂H₄/O₂ and C₂H₄/C₂H₂/O₂ combustion flame for diamond deposition with and without a CO₂ laser excitation. Strong emissions from radicals C₂ and CH were observed in the visible range in all the OES spectra acquired. By adding a continuous-wave CO₂ laser to irradiate the flame at a wavelength of 10.591 μm, the common CO₂ laser wavelength, it was discovered that the emission intensities of the C₂ and CH radicals were increased due to the laser beam induced excitation. OES measurements of the C₂ and CH radicals were performed using different gas combinations and laser powers. The rotational temperatures in the flame were determined by analyzing the spectra of the R-branch of the A²Δ→X²Π (0, 0) electronic transition near 430 nm (CH band head). Information obtained from the OES spectra, including the emission intensities of the C₂ and CH radicals, the intensity ratios, and the rotational temperatures, was integrated into the study of diamond deposition on tungsten carbide substrates for mechanism analysis of the laser induced vibrational excitation and laser-assisted diamond deposition.

Femtosecond laser micromachining by filamentation is used to fabricate volumetric optical elements in polymer materials. In this paper, we review the induction of filamentary refractive index modifications and its application to the fabrication of diffractive optical elements in various polymer materials.

Micro-lenses, including Fresnel-Lenses, were fabricated by excimer laser ablation of polymers by means of lasergenerated grey-tone-masks. The smallest reproducible holes that could be fabricated by excimer laser ablation (193 nm, 1 J/cm²) of chromium-on-quartz (thickness 50-100 nm) were around 3 μm, the pitch of which should be at least at the same value to ensure a reproducibility of hole-arrays. To achieve acceptable ablation times during the fabrication of the grey-tone-masks, on-the-fly ablation instead of step-and-repeat technique was used, operating the laser at a constant pulse repetition rate <30 Hz with a continuously moving quartz-substrate. In this way and using different encoding techniques it was possible to generate at least 11 different grey-tones. The available grey-tones were used to generate grey-tone-masks for ablation of Polymethylmethacrylate (PMMA) and Polycarbonate (PC). For that, fluences in the range of 0.07-0.14 J/cm² could be applied, corresponding to a value of 1.25 J/cm² on the workpiece without grey-tonemask and a value lying well below the damage threshold of the chromium mask. Refractive micro-lenses fabricated in this way did not show a good imaging quality, since 11 grey-tones is less than required to generate a continuous surface profile over the full diameter of the lens during ablation and the achievable aspect ratio is limited with the small fluences. However, flat diffractive micro-lenses of the Fresenel type with a quasi-continuously surface profile could be fabricated in a sufficient manner. This can be attributed to the fact that each segment of the Fresenel-lenses can be encoded by 11 grey-tones, leading to much smoother surface reliefs and to a sufficient imaging quality.

Recently, hybrid integration of multifunctional micro-components for creating complex, intelligent micro/nano systems has attracted significant attention. These micro/nano systems have important applications in a variety of areas, such as healthcare, environment, communication, national security, and so on. Until now, fabrication of micro/nano systems incorporated with different functions is still a challenging issue, which generally requires fabrication of microcomponents beforehand followed by assembly and packaging procedures. Thus, the fabrication process is complex and costly. In recent years, the rapid development of femtosecond laser microfabrication technology has enabled direct fabrication and integration of multifunctional components, such as microfluidics, microoptics, micromechanics, microelectronics, etc., into a substrate. Particularly, in this talk, we show the use of femtosecond laser microfabrication for integrating microelectronics and microphotonics. Both microelectrodes and optical waveguides can be directly embedded in active materials after a femtosecond laser direct writing followed by electroless chemical plating. As examples, electric-optic (EO) modulators were fabricated in lithium niobate (LiNbO₃) crystal and their functions were demonstrated.

Femtosecond laser based micromachining technologies have the inherent capability of producing elements in 3D. Their ability of rapid prototyping can be exploited to develop novel Optofluidics devices. Microfluidic channels were fabricated and integrated with optical waveguides using a single femtosecond laser. Optically pumping the microchannel filled with polyfluorene solution and by dispersing nanoparticles in the solution, random lasing in the microchannel is obtained. We demonstrate a novel approach to organic photonic devices, where the unique properties of a conjugated polymer in solution are exploited in a microfluidic configuration in order to produce easy-to-integrate photonic devices.

Femtosecond laser direct writing in glass materials represents a simple single-step approach to generate threedimensional (3D) optical circuits that cannot be constructed with traditional fabrication techniques. In this paper, we present an attractive extension of such femtosecond laser processing to the writing of optical circuits directly inside the cladding of single-mode optical fiber. To enable the formation of strongly guided and undistorted waveguide modes within the small cylindrical fused silica volume (125 μm diameter), frequency-doubled (λ = 522 nm) Ytterbium fiber-amplified femtosecond laser light at high repetition rate (500 kHz) was tightly focused with a high 1.25 numerical aperture (NA) oil immersion lens. In this way, low-loss waveguides could be arbitrarily located in various cladding positions without generating ablation damage. Basic components such as directional couplers were demonstrated that present a new means for dense integration of optical elements that couple with the nearby fiber core. Such 3D all-fiber optical circuits represent practical tools to bypass tedious assembly and packaging steps such as fiber pigtailing with planar lightwave components. This formation of optical circuits directly within the cladding of optical fiber opens new prospects for manufacturing compact and functional optical and optofluidic microsystems for Telecom, sensing and lab-on-a fiber applications.

As the new method of machining, laser ablation has a lot of attractive advantages. The possibilities of dead end engraving and stable long term machining would be the great merits of micro-patterning to large metal mold which is used to the optical sheets for flat panel display for example. We developed pico-second laser machining system and manufactured micro-patterns on metal mold surface. And from those sample-machining results, we concluded it is possible to adapt this system to metal mold micro-pattern machining and decided to continue our development of laser machining.

High-precision micromachining with picosecond lasers became an established process. Power scaling led to industrial lasers, generating average power levels well above 50 W for applications like structuring turbine blades, micro moulds, and solar cells. In this paper we report, how a smart distribution of energy into groups of pulses can significantly improve ablation rates for some materials, also providing a better surface quality. Machining micro moulds in stainless steel, a net ablation rate of ~1 mm³/min is routinely achieved, e.g. using pulse energy of 200 μJ at a repetition rate of 200 kHz. This is industrial standard, and demonstrates an improvement by two orders of magnitude over the recent years. When the energy was distributed to a burst of 10 pulses (25 μJ), repeated with 200 kHz, the ablation rate of stainless steel was 5 times higher with the same 50 W average power. Bursts of 10 pulses repeated with 1 MHz (5 μJ) even resulted in an ablation rate as high as 12 mm³/min. In addition, optimized pulse delays achieved a reduction of the surface roughness by one order of magnitude, providing Ra values as low as 200 nm. Similar results were performed machining silicon, scaling the ablation rate from 1.2 mm³/min (1 pulse, 250 μJ, 200 kHz) to 15 mm³/min (6 pulses, 8 μJ, 1 MHz). Burst machining of ceramics, copper and glass did not change ablation rates, only improved surface quality. For glass machining, we achieved record-high ablation rates of >50 mm³/min, using a new state-of-the-art laser which could generate >70 W of average power and repetition rates as high as 2 MHz.

In this paper, a dual-beam laser micromachining system consisting of a femtosecond (fs) laser and a nanosecond (ns) laser has been developed to enhance the ablation efficiency. Experiments were conducted in different materials including dielectric (fused silica), semiconductor (silicon wafer), and metal (aluminum alloys). The amount of material being removed was determined for fs pulses alone, ns pulses alone, and pairs of fs and ns pulses with different time lags in between. It was found that the material removal efficiency increases in the dual-beam process for all materials being studied as compared to the fs alone or ns alone, particularly for dielectrics. The highest ablation efficiency for fused silica occurs when the fs pulse is shot near the peak of the ns pulse envelope. A corresponding numerical model for dual beam ablation of dielectrics was also developed by integrating the plasma model, the improved two-temperature model, and Fourier's law to understand the laser-material interaction. It was found that the fs laser pulse can significantly increase the free electron density and change the optical properties of the dielectric, leading to the increase of absorption for the subsequent ns pulse energy. This study provides a fundamental understanding for the enhancement of material ablation efficiency, particularly for wide-bandgap dielectrics.

Laser ablation milling with ultra short pulsed Nd:YAG lasers enables micro structuring in nearly all kinds of solid materials like metals, ceramics and polymers. A precise machining result with high surface quality requires a defined ablation process. Problems arise through the scatter in the resulting ablation depth of the laser beam machining process where material is removed in layers. Since the ablated volume may change due to varying absorption properties in single layers and inhomogeneities in the material, the focal plane might deviate from the surface of the work piece when the next layer is machined. Thus the focal plane has to be adjusted after each layer. A newly developed optical and acoustical process control enables an in-process adjustment of the focal plane that leads to defined process conditions and thus to better ablation results. The optical process control is realized by assistance of a confocal white light sensor. It enables an automated work piece orientation before machining and an inline ablation depth monitoring. The optical device can be integrated for an online or offline process control. Both variants will be presented and discussed. A further approach for adjustment of the focal plane is the acoustical process control. Acoustic emissions are detected while laser beam machining. A signal analysis of the airborne sound spectrum emitted by the process enables conclusions about the focal position of the laser beam. Based on this correlation an acoustic focus positioning is built up. The focal plane can then be adjusted automatically before ablation.

Due to current and future anticipated widespread use of thin silicon wafers in the microelectronics industry, there is a large and growing interest in laser-based wafer dicing solutions. As the wafers become thinner, the laser advantage over saw dicing increases in terms of both the speed and yield of the process. Furthermore, managing the laser heat input during the dicing process becomes more important with increasingly thin wafers and with increasingly narrow saw streets. In this work, shaped-beam laser-cutting of thin (100 μm and below) silicon is explored with Newport / Spectra- Physics Pulseo 20-W nanosecond-pulse 355-nm DPSS q-switched laser system. Optimal process conditions for cutting various depths in silicon are determined, with particular emphasis on fluence optimization for a narrow-kerf cutting process. By shaping the laser beam into a line focus, the optimal fluence for machining the silicon can be achieved while at the same time utilizing the full output power of the laser source. In addition, by adjusting the length of the laser line focus, the absolute fastest speed for various cutting depths is realized. Compared to a circular beam, a dramatic improvement in process efficiency is observed.

The nonlinear mechanisms of femtosecond laser damage allow tight control of ablation to precisely remove very small amounts of material, leaving holes as small as tens of nanometers wide. By serially targeting laser pulses in glass, a host of three dimensional nano- and microfluidic structures can be formed including nozzles, mixers, and separation columns. Recent advances allow the formation of high aspect ratio nanochannels from single pulses, thus helping address fabrication speed limitations presented by serial processing. Femtosecond nanomachining is enabling for a variety of applications including nanoscale devices for analytic separations, chemical analysis, and biomedical diagnostics.

Direct laser writing via two-photon absorption allows the fabrication of three-dimensional dielectric structures with submicron resolution by tightly focusing ultrashort laser pulses into a photo-sensitive material with a high-resolution microscope objective and scanning the laser focus relative to the material. Woodpile photonic crystals fabricated with this method show a characteristic dip in transmission at near-infrared wavelengths. The spectral position of this transmission dip scales with the grating period of the fabricated crystals. Metallo-dielectric structures can be obtained by first fabricating dielectric templates with direct laser writing and subsequently coating the templates with a thin conformal metal film by electroless plating. Contiguous and conducting silver films can be deposited even on convoluted 3D geometries.

Low temperature crystallization and the micropatterning of lead zirconate titanate (PZT) film were achieved by laser direct writing method using a sol-gel derived precursor film. After scanning of an Ar ion laser beam through an objective lens, the etching of the unirradiated area of the precursor film with an acidic solution gave micropatterns with a resolution of several ìm. The formation of crystalline micropatterns was confirmed by micro-Raman spectroscopy. The laser direct writing method provides a low-temperature processing of crystalline PZT film while the crystallization of PZT needs the heat treatment above 600 °C in the case of convenient methods. The influences of the power density of the laser beam were investigated. With increasing the laser power density, the change from tetragonal to rombohedral phase was observed. The micropattern with tetragonal phase showed residual carbon. The carbon contamination could be removed by heat treatment in air. The direct laser writing of crystalline barium titanate (BT) film was also successfully performed using sol-gel derived BT films containing BT nano-crystalline seeds. The dielectric constant of the crystalline BT micropatterns reached 76.2 at 100 kHz.

The material development for advanced lithium ion batteries plays an important role in future mobile applications and energy storage systems. It is assumed that electrode materials made of nano-composited materials will improve battery lifetime and will lead to an enhancement of lithium diffusion and thus improve battery capacity and cyclability. Lithium cobalt oxide (LiCoO₂) is commonly used as a cathode material. Thin films of this electrode material were synthesized by non-reactive r.f. magnetron sputtering of LiCoO₂ targets on silicon or stainless steel substrates. For the formation of the high temperature phase of LiCoO₂ (HT-LiCoO₂), which exhibits good electrochemical performance with a specific capacity of 140 mAh/g and high capacity retention, a subsequent annealing treatment is necessary. For this purpose laser annealing of thin film LiCoO₂ was investigated in detail and compared to conventional furnace annealing. A high power diode laser system operating at a wavelength of 940 nm with an integrated pyrometer for temperature control was used. Different temperatures (between 200°C and 700°C) for the laser structured and unstructured thin films were applied. The effects of laser treatment on the LiCoO₂ thin films studied with Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction to determine their stoichiometry and crystallinity. The development of HT-LiCoO₂ and also the formation of a Co₃O₄ phase were discussed. The electrochemical properties of the manufactured films were investigated via electrochemical cycling against a lithium anode.

Laser structuring of different types of thin film layers is a state of the art process in the photovoltaic industry. TCO layers and molybdenum are structured with e.g. 1064 nm lasers. Amorphous silicon, microcrystalline silicon or cadmium telluride are ablated with 515/532 nm lasers. Typical pulse durations of the lasers in use for these material ablation processes are in the nanosecond range. Up to now the common process for CIS/CIGS cells is needle structuring. Hard metal needles scribe lines with a width of 30 to 60 μm into the semiconductor material. A laser technology would have some advantages compared to mechanical scribing. The precision of the lines would be higher (no chipping effects), the laser has no wear out. The dead area (distance from P1 structuring line to P3 structuring line) can be significantly smaller with the laser technology. So we investigate the structuring of CIS/CIGS materials with ultra short pulse lasers of different wavelengths. The ablation rates and the structuring speeds versus the repetition rates have been established. For the different layer thicknesses and line widths we determined the necessary energy densities. After all tests we can calculate the possible reduction of the dead area on the thin film module. The new technology will result in an increase in the efficiency per module of up to 4 %.

In this paper we will discuss the fundamental aspect of ablation processes by using laser beams of different intensity profiles and cross sections. For characterizing the efficiency of pulse energy for the ablation process the effective energy efficiency and the effective overall efficiency can be used. The effective energy efficiency and effective overall efficiency of laser beams with circular Gaussian profile and two dimensional top-hat profile will be given. The circular Gaussian profile with a maximum effective overall efficiency of 30% is the most inefficient beam for ablation process. Ideal two dimensional top-hat profile has 100% effective overall efficiency and is the most efficient choice for thin film ablation process. Also the lowest influence of waste energy during ablation process with two dimensional top-hat profile is expected. In the talk energy and cost effective system concepts for "green processing" at high through put and application results in photovoltaic will be discussed.

Laser processing is an important application for fabrication of silicon solar cells, e.g. buried contacts, laser fired contacts or edge isolation. At Fraunhofer ISE a liquid-jet guided laser is used for Laser Chemical Processing (LCP). Both the fundamentals of laser material ablation with this system and the application of various processes for solar cell fabrication are investigated. The applications are divided into two main areas: Microstructuring and deep laser cutting (wafering) of silicon substrates. Microstructuring contains the investigation and characterization of laser induced damage and selective emitter formation for n- and p-type emitters depending on laser parameters and liquid properties. One of the most important and industrially relevant topics at the moment is the formation of a selective highly doped emitter under the metal fingers of solar cells. Wafering deals with the evaluation of suitable laser parameters, adequate chemicals or chemical additives and the understanding of ablation processes by simulation and experimental work. In this presentation newest results concerning n-type doping for varying laser and liquid parameters will be presented with regard to cell efficiency and contact resistance. Furthermore a short overview of promising LCP applications will be given, e.g. p-type doping and wafering.

For semiconductor manufacturing, a mature industry, a number of laser techniques are employed in production. Diodepumped solid-state (DPSS) lasers are used in applications that cannot be performed by mechanical, chemical, or other laser fabrication methods as well as where they add value through increased throughput and/or improved process quality. Applications such as edge isolation, wafer scribing/dicing, via formation, laser doping and annealing for Semicon are being applied to crystalline silicon PV manufacture as well as research and development for the next generation of high efficiency cells. Similarly, selective material removal for exposing underlying layers without thermal damage is vital in the production of thin film PV panels. In this paper, some of the most important applications of lasers along with experimental results will be reviewed to illustrate how laser methods can have a significant impact on the development and productivity of the photovoltaic industry.

We report on the selective structuring of CIS (Cu(In,Ga)(S,Se)₂) thin film solar cells applying picosecond lasers at 1064 nm. For a monolithic serial interconnection the thin layers are selectively separated by so called laser patterns 1, 2 and 3 (P1, P2 and P3). We demonstrate that the half micron thick molybdenum back electrode can be structured with a P1 process speed of more than 4 m/s without detectable residues and damages by direct induced laser ablation from the back side. A CIS layer (~2 μm thickness) is structured by standard direct laser ablation at higher energy densities and a process speed up to 200 mm/s. A 1.5 μm thick ZnO front electrode layer can be line separated with P3 speed up to several 1000 mm/s by indirect induced laser ablation. We demonstrate that direct induced (P1) and indirect induced (P3) picosecond laser ablation are not purely thermal processes working at energy densities far below the evaporation enthalpy. To increase the scribing speed elliptical and rectangular beam profiles were investigated. Validation of the processes for functionality within a CIS solar cell will be presented.

In a semi-conductor optical amplifier (SOA) as in any other optical devices, the performances that can be reached is strongly dependent on the chip temperature. For example, the optical output power of a laser or the optical gain in a SOA is reduced when the temperature of the junction increases. This latter can be controlled or monitored thanks to a thermo-electronic cooler (or a Peltier element) and a thermistor. In this paper, we first have calculated the thermal resistance of various semiconductor structures such as buried or ridge waveguides lasers. We then calculate the Peltier consumption necessary to maintain a given temperature. The influence of the thermistor position as well as the module conception have been investigated in these calculation. The size of the different mechanical elements, the nature and thermal properties of the material use for the module fabrication have been found to play an important role in the thermal performance of the optical modules. The Peltier size is defined by maximizing its efficiency. It depends on the power to be dissipated as well as the temperature operation of the device. The latter depends on the performance expected by the optical devices. We discussed the optimization of the device structure associated to its packaging to find the best compromise between performance and electrical consumption. The trade-off found depends on the temperature at which the device operates as well as on the thermal power to be dissipated.

A technique is suggested to measure a threshold of two-photon initiated photopolymerisation involving Z-scan of a thin film of sensitive material along the focusing axis of the laser beam. The condition of reaching the threshold when gradually increasing the light intensity by moving the film towards the focal spot of the beam is defined as that with minimal intensity at which polymerization occurs. The occurrence of the polymerization is detected by interferometric effect inside the transmitted beam itself, which is due to interference of the wave going through the polymerization area and the wave going around it. The technique is demonstrated for measurements employing Nd:YAG laser in nanosecond regime with fundamental frequency 1064 nm and its harmonic of 532 nm, as well as with pumped by its third harmonic optical parametric oscillator. Threshold data are presented for particular systems, indicating threshold of 5 GW/cm² for a system based on Rose Bengal exposed by 1064 nm nanosecond-pulsed radiation and 0.05 GW/cm² for Darocur initiators exposed to 532 nm.

Single pulse femtosecond laser damage in transparent dielectrics has been shown to occur through nonlinear damage mechanisms that can allow material removal on scales well below the classical limit of the order of the wavelength of the incident light. These mechanisms can be harnessed to allow the optical machining of devices on the nanoscale. We observe the formation of high aspect-ratio nanochannels by single femtosecond pulses. These channels, several microns in length, can be formed at the front or rear surface of a sample, corresponding to conditions under which spherical aberration is expected and where it is minimized. The presence of similar channels at both locations suggests that aberration does not play a critical role in nanochannel creation, and we present evidence supporting a dominant role of self focusing and microscale filamentation. Applications for these long nanoscale diameter channels include nanopores, nanowells, or out-of-plane vias. The ability to generate these channels with single pulses allows rapid fabrication that complements existing techniques, thus addressing a major limitation to fabrication of microfluidics and nanopores.