Novel glazing with embedded micro-mirrors can significantly reduce the energy consumption due to cooling and lighting in buildings. Especially promising are large arrays of periodic micro compound-parabolic-concentrators (CPCs) with angular-selected transmittance. For the production of micro CPCs, curved sidewall grooves with a controlled optical surface and an aspect ratio of about 2.3 are fabricated on polycarbonate substrates by scanning nanosecond 248-nm excimer laser ablation. The likewise obtained microstructures can be used as master mold for replication. The cross-sections of the micro grooves are characterized by confocal microscopy, and the extracted morphologies are used for the ray-tracing simulation of the optical devices. Prior to the scanning ablation using a suitable mask in the optical path, the depth profiles under static ablation are investigated to identify ablation rate, imaging resolution and produced surface. Interestingly for the width of the mask opening being less than 6 μm, the ablation rate is increased due to optical interference and /or less shielding by debris. Concerning the scanning ablation, the depth of the curved sidewall grooves ranges from 48 μm to 114 μm, corresponding to the width of the groove opening being in the range from 20 μm to 50 μm. The observed final shapes in cross-sections are in good agreement with the design of the mask. For both theoretical and fabricated groove shapes, the angular-selected transmittance profiles predicted from ray-tracing simulations are highly similar. Scanning nanosecond excimer laser ablation is therefore a promising approach for the realization of high-quality micro CPCs.
Focused electron beam induced processing (FEBID) equipments are the "all in one" tools for high resolution
investigation, and modification of nano-devices. Focused electron beam induced deposition from a gaseous precursor usually
results in a nano-composite sub-structured material, in which the interesting material is embedded in an amorphous
carbonaceous matrix. Using the Hydrogen free tetraisocyanatosilane Si(NCO)<sub>4</sub> molecule as Si source, we show how a
controlled oxygen flux, simultaneously injected with the precursor vapors, causes contaminants to vanish from the FEB
deposits obtained and leads to the deposition of pure SiO<sub>2</sub>. The chemical composition of the FEBID material could be
controlled from SiC<sub>2</sub>NO<sub>3</sub> to SiO<sub>2</sub>, the latter containing undetectable foreign element contamination. The [O<sub>2</sub>] / [TICS] ratio
needed to obtain SiO<sub>2</sub> in our FEB deposition equipment is larger than 300. The evolution of the FEBID material chemical
composition is presented as function of the [O<sub>2</sub>] / [TICS] molecular flux ratios. A hypothetical decomposition pathway of
this silane under these conditions is discussed based on the different species formed under electron bombardment of TICS.
Transmission electron microscopy investigations demonstrated that the deposited oxide is smooth (roughness sub 2nm) and
amorphous. Infrared spectroscopy confirmed the low concentration of hydroxyl groups. The Hydrogen content of the
deposited oxide, measured by elastic recoil detection analysis, is as low as 1 at%. 193nm wavelength AIMS investigations of
125nm thick SiO<sub>2</sub> pads (obtained with [O<sub>2</sub>] / [TICS] = 325) showed an undetectable light absorption.
Nano-optical devices are raising more and more interest for a variety of applications. From single molecule detection at high molecular concentration by Fluorescence Correlation Spectroscopy (FCS) through optical multiplexing with photonic crystal structures into the exciting field of negative index of refraction materials, the hardware functional dimensions and surely the tolerances are reaching the lower tens of nanometer range. The fabrication of such devices,
i.e. the machining of optically interesting materials and material combinations (dielectric, semiconducting, or metallic) at this scale needs adaptation of classical nanostructuring technologies like Electron Beam Lithography (EBL), or the application of serial direct machining technologies like Focused Charged Particle Beam Etching or Deposition with electrons or Ga ions. For low excitation volume FCS measurements, EBL is used for production of high quality nanoscale
sub-wavelength apertures in optically opaque (150 nm thick) metal films. The process consists in high aspect ratio patterning of a thick negative e-beam resist film followed by metal lift off. The optically transparent substrate allows the production of any 2D aperture geometry. Difficulties of the production process and their limits are presented. Direct serial machining with charged particle beams shows excellent flexibility and is an interesting 3D alternative method. Deposition by decomposing volatile chemicals under an ion/electron probe, which can be as small as 7nm/1nm, this
technique allows for rapid, local prototyping of 2D and 3D nano-structures with highest lateral and axial resolution. The deposited material can be tuned to homogeneous, nanocomposite or crystalline, metallic or transparent, opening the way to applications in photonic crystals and plasmonics. An original in-situ micro-reflectometry method permits the real time control of the growth of the deposits.
The coupling of a laser focused into a water microjet is studied. Using a high-power laser, the light guided in the jet is used to process various materials. To explain the observed ablation patterns, the propagation of a low-power and highly coherent laser beam coupled into a laminar water jet is studied. The light of a He-Ne laser (5 mW) is focused into the water jet, which behaves as a multimode waveguide. The distribution of the light intensity in the jet impinging on a glass plate cutting the jet perpendicularly to its propagation direction is recorded for various laser coupling conditions. The influence of the jet diameter, as well as the influence of the depth of focus of the incident beam and its position with respect to the center of the jet is studied. A nearly homogeneous grain size was observed over the whole jet cross section. The characteristic grain size was then compared with predictions from standard multimode fiber theory. Finally, it is confirmed that the structures resulting from material ablation using the laser-microjet technology when coupling Q-switched Nd:YAG (=1064 and 355 nm) are closely related to the predicted light intensity distributions. Furthermore, recommendations are made concerning the coupling conditions for optimizing the laser processing applications.
We report on the fabrication of Ti:sapphire channel waveguides. Such channel waveguides are of interest, e.g., as low-threshold tunable lasers. We investigated several structuring methods including ion beam implantation followed by wet chemical etching strip loading by polyimide spin coating and subsequent laser micro-machining, direct laser ablation or reactive ion etching through laser-structured polyimide contact masks. The later two methods result in ribs having different widths and heights up to ~5 μm. By reactive ion etching we have obtained channel waveguides with strong confinement of the Ti:sapphire fluorescence emission.
The focused electron beam of an electron microscope (SEM or TEM) decomposes tailored precursor molecules on substrates into functional deposits. Extremely high aspect ratios of more than 10 can easily be obtained. During the last years several materials could be deposited, most of them composed of metal nanoparticles embedded in amorphous matrices. The deposition process depends on the precursor supply, its surface adsorption behavior, and the beam induced chemical decomposition path of the molecule on one hand, and on the other hand on the electron beam properties like beam current, electron energy, and beam distribution. The limits in minimal size, growth rate, and chemical composition arise from all mentioned parameters, which are interdependent.
Monitoring biological relevant reactions on the single molecule level by the use of fluorescent probes has become one of the most promising approaches for understanding a variety of phenomena in living organisms. By applying techniques of fluorescence spectroscopy to labelled molecules a manifold of different parameters becomes accessible i.e. molecular dynamics, energy transfer, DNA fingerprinting, etc... can be monitored at the molecular level.
However, many of these optical methods rely on oversimplified assumptions, for example a three-dimensional Gaussian observation volume, perfect overlap volume for different wavelength, etc. which are not valid approximations under many common measurement conditions. As a result, these measurements will contain significant, systematic artifacts, which limit their performance and information content.
Based on Fluorescence Correlation Spectroscopy (FCS) and Fluorescence Lifetime Spectroscopy we will present representative examples including a thorough signal analysis with a strong emphasis on the underlying optical principles and limitations. An outlook to biochip applications, parallel FCS and parallel Lifetime measurements will be given with cross links to optical concepts and technologies used in industrial inspection.
We present an intelligent sensor, consisting in 2 CCDs with different field of view sharing the same optical motion, which can be controlled independently or not in their horizontal, vertical and rotational axis, and are connected in a closed loop to image processing resources. The goal of such a sensor is to be a testbed of image processing algorithms in real conditions. It illustrates the active perception paradigm and is used for autonomous navigation and target detection/tracking missions. Such a sensor has to meet many requirements : it is designed to be easily mounted on a standard tracked or wheeled military vehicle evolving in offroad conditions. Due to the rather wide range of missions UGVs may be involved in and to the computing cost of image processing, its computing resources have to be reprogrammable, of great power (real-time constraints), modular at the software level as well as at the hardware level and able to communicate with other systems. First, the paper details the mechanical, electronical and software design of the whole sensor. Then, we explain its functioning, the constraints due to its parallel processing architecture, the image processing algorithms that have been implemented for it and their current uses and performances. Finally, we describe experiments conducted on tracked and wheeled vehicles and conclude on the future development and use of this sensor for unmanned ground vehicles.
Excimer laser ablation of a scanned substrate can be used for prototyping of lab-on-a-chip microfluidic channels . Here, the relationship between the wetting properties of the channels and the irradiation conditions is described. The wetting properties are quantified by electro-osmotic flow measurements in channels, produced with different conditions of scanning ablation. The observed variations can be explained in terms of a competition between a direct and an indirect redeposition pathway for the debris.
Three different approaches to fast in situ processing of metal contacts are studied. The goal is to make high density interconnects with width, thickness and pitch respectively of the order of 10, 5 and 25 microns. The direct writing speed should be equal to or faster than 1 cm per second, while maintaining good electrical conductivity and surface adhesion of the metal stripes. The first approach is the classical laser chemical vapor deposition of copper from its bishexafluoroacetylacetonate (Cubishfa) precursor, which is pushed towards the practical limits of maximum writing speed. Seeding of the transparent glass-like substrates with layers of different metals and oxides which are extremely thin helps to increase the writing speed of this process significantly without substantially influencing the substrate's electrical properties. Writing speeds close to 1 cm l are attained. The second approach is to deposit metal from surface layers of metalorganic (MO) cluster compounds like Au55(P03)12Cl6 which have advantageous thermochemistry for the decomposition as well as a high metal content in the MO precursor. Such compounds can be decomposed with a laser to yield quite pure gold lines at speeds up to 10 cm s1. Such layers are also irradiated with ion and electron beams in an effort to try to make submicron metal contacts. The third approach consists of a fast in situ step in which the surface is locally prenucleated by decomposing an ultrathin MO layer with a photon or particle beam. In a second slow parallel processing step, a large number of prenucleated substrates are then "developed". The latter implies the selective metal deposition exclusively on top of the prenucleated stripes to create several micron thick metallic electrical contacts. We report on the selective metal deposition on ultrathin Pt prenucleation layers by electroless deposition from a copper sulfate bath, by decomposition from a copper formate solid surface layer, and by low pressure chemical vapor deposition from gaseous Cubishfa. Prenucleation was also tested with other metals.