Reinhard Noll

Fraunhofer Institute for Laser Technology ILT | ILT · Fraunhofer Institute for Laser Technology

In general, light scattering comprises any kind of interaction of light with matter, in which the light is not absorbed permanently. This definition includes the effects of reflection and refraction. In a narrower sense, the term light scattering deals only with interaction processes with microscopic particles, e.g. atoms or dust particles.

Inverse production strives for a selective dismantling of industrial mass products at their end-of-life (EOL) with the goal to generate highly enriched fractions of valuable materials for subsequent tailored recovery procedures. Since in many cases there is only fragmentary or even no information available about the chemical composition of such EOL...

The material ablation of focused laser pulses is an important aspect of laser-induced breakdown spectros-copy (LIBS). It has frequently been used to ablate non-representative layers from the surface or to...

Within the European project ADIR (www.ADIR.eu), a consortium of R&D institutes and companies have developed processes and machines to demonstrate the feasibility of a novel approach for an automated selective disassembly of consumer and professional electronics. The target of the ADIR project is to use selective physical separation methods to impro...

Am Ende der Lebensdauer elektronischer Produkte gehen immer noch viele der darin enthaltenen Wertstoffe verloren. Mithilfe moderner produktionstechnischer Methoden könnten diese Produkte gezielt zerlegt werden, um hochwertige Sortierfraktionen zu gewinnen. Der Beitrag zeigt Ansätze zu diesen Herausforderungen der inversen Produktion auf. Beispielha...

Measuring distances in the range between a few centimetres and a few metres are of special interest for automated industrial LIBS applications. They allow for a reliable optical access to measuring objects in a process line under harsh industrial environments. In that range a compromise can be found between the conflicting requirements with respect...

The European project ADIR – running since 9/2015 – coordinated by the Fraunhofer Institute for Laser Technology fits in with the subject of metals recovery from electronic waste. The goal of the ADIR project is to demonstrate the feasibility of a key technology for next generation urban mining in the scope of inverse production concepts. An automat...

An overview will be presented on current R&D activities of the European project ADIR-running since 9/2015-dealing with the automated disassembly, separation and recovery of valuable materials from electronic equipment. Main focus are end-of-life cell phones and printed circuit boards from server and network electronics. To date the material specifi...

Hard-tissue ablation was already investigated for a broad variety of pulsed laser systems, which cover almost the entire range of available wavelengths and pulse parameters. Most effective in hard-tissue ablation are Er:YAG and CO2 lasers, both utilizing the effect of absorption of infrared wavelengths by water and so-called explosive vaporization,...

To analyse continuous casting steel blooms a removal of non-representative surface layers is required prior to the analysis. In this work, an optimized process is developed to ablate such layers and to analyse the bulk material underneath with laser-induced breakdown spectroscopy (LIBS). A high ablation rate is crucial since the time slot for an in...

In a miniaturised flow switch fluid flows are controlled by reducing the local viscosity via absorption of laser radiation. Through this, the local flow rates are increased to switch the outlet port of a fluid flow carrying the analyte. The microfluidic chip is fabricated using Selective Laser-Induced Etching (SLE). SLE allows novel 3D-hydrodynamic...

The principle of holography is introduced comprising the formation of virtual and real images of the reconstructed object. Holographic interferometry allows to make visible slight changes of the object shape as those induced by deformations or vibrations. The quantitative determination of the displacement vector with the help of the phase-shifting...

At first, we summarize the properties of a transverse electromagnetic wave. This is followed by the discussion of the diffraction of light. We present the concept of coherence—temporal and spatial—and compare laser radiation with thermal light. After that, we treat the Gaussian beam and the higher transverse modes. An overview of typical laser para...

First, we explain the basics of interferometry. Then we deal with distance measurement using a polarization interferometer and a dual-frequency interferometer. This discussion also includes angular and straightness measurements. Finally, the Twyman-Green interferometer is presented, which can be used for testing the quality of optical imaging compo...

The basic principle of laser-induced fluorescence and fluorescence spectroscopy is presented to detect organic molecules with high sensitivity. We present various variants of this method: fluorescence correlation spectroscopy, fluorescence polarization spectroscopy, time-resolved fluorescence analysis. Examples of applications range from the inline...

The formation of speckles while illuminating an object with a laser beam is described. Different types of speckle interferometers are presented to measure out-of-plane, in-plane or derivatives of object displacements. The set-up of an electronic speckle interferometer is shown and examples of applications are given ranging from deformation analysis...

Different kinds of light detectors and their working principles are explained covering the following detector types: thermal detectors, photoelectric detectors, semiconductor detectors, space-resolving detectors. This is followed by the discussion of some general principles of electronic metrology, which must be considered when applying these detec...

Initially the particle concept of light is explained. Then we present the different kinds of interaction of light and matter. We start with the reflection and refraction, followed by the discussion of linear and non-linear absorption of light. The most important light scattering processes are described: Rayleigh, Mie and Raman scattering. Finally,...

We give an overview of confocal microscopy, discuss the physical principle and the achievable resolution. Different kinds of scanners are presented and some typical applications. In the second section we show, that a confocal measurement system can also be used to measure the surface profile of non-transparent objects. Finally, we discuss optical d...

Laser spectroscopy utilizes the specific properties of atoms and molecules to gain information about the chemical composition of the test object. The principle of laser material analysis is described as well as the important underlying physical processes. The evaluation of the emitted spectra yields the composition of the material. Examples of appl...

Optical coherence tomography (OCT) allows to measure geometric features inside translucent objects such as organic materials or organic tissues. The principle is based on interferometry. Time-domain and Fourier-domain methods are applied to make visible differences in the refractive index profile of the measuring object. We present the set-up of OC...

This chapter is divided in three parts. In the first section, various optical components for beam guiding and beam shaping are presented. In particular, we treat beam deflection, beam splitting, the modulation of polarization, intensity, wavelength and phase. This is followed by a section on beam shaping and focusing of a Gaussian beam. In the last...

Laser triangulation is a method to measure the absolute distance to an object. The principle of triangulation is presented including the extensions to 2-D and 3-D measurements. We discuss the characteristic curve of laser triangulation, the implications of the laser beam propagation and the properties of the object surface. Examples of applications...

Laser Doppler methods are used to measure the state of motion of objects and particles. Laser vibrometers and laser anemometers make use of this effect. Their interferometric principle is explained which allows to determine velocities and to discriminate as well the direction of movement. Signal processing schemes are described such as frequency de...

Introduction.- Properties of Laser Radiation.- Interaction of Laser Radiation and Matter.- Beam Shaping and Guiding.- Detection of Electromagnetic Radiation.- Laser Interferometry.- Holographic Interferometry.- Speckle Metrology.- Optical Coherence Tomography.- Laser Triangulation.- Laser Doppler Methods.- Confocal Measurement Systems.- Laser Spect...

Laser-induced breakdown spectroscopy (LIBS) is applied for the inline analysis of liquid slag at a steel works. The slag in the ladle of a slag transporter is measured at a distance of several meters during a short stop of the transporter. The slag surface with temperatures from ≈600 to ≈1400 °C consists of liquid slag and solidified slag parts. Au...

This paper presents R&D activities in the field of laser-induced breakdown spectroscopy for industrial applications and shows novel LIBS systems running in routine operation for inline process control tasks. Starting with a comparison of the typical characteristics of LIBS with XRF and spark-discharge optical emission spectrometry, the principal st...

The identification and separation of different alloys are a permanent task of crucial importance in the metal recycling industry. Laser-induced breakdown spectroscopy (LIBS) offers important advantages in comparison to the state-of-the-art techniques for this application. For LIBS measurement no additional sample preparation is necessary. The overa...

Several laser systems in the infrared wavelength range, such as Nd:YAG, Er:YAG or CO2 lasers are used for efficient ablation of bone tissue. Here the application of short pulses in coaction with a thin water film results in reduced thermal side effects. Nonetheless up to now there is no laser-process for bone cutting in a clinical environment due t...

The determination of types and size distributions of inclusions in steel samples from Optical Emission Spectrometry with Pulse Discrimination Analysis (OES/PDA) data requires advanced mathematical tools. The main task is to filter out those OES/PDA events that correspond to inclusions in contrast to volume events, i.e. to find reliably the outliers...

Sensitive fluorescence sensors are needed to measure single cell properties in microfluidic devices. Optimizing the parallelizability and the measurement volume are two options enabling high throughput applications. The fluorescence sensor presented is highly parallelizable and, due to MEMS micromirror arrays, several sensors can be integrated in o...

The interaction of the pulsed laser beam with the material causes an ablation of mass from a liquid or solid measuring object. This mass is partially evaporated and transferred into the plasma state, where the species are excited to emit element-specific radiation used for LIBS. However, a part of the ablated mass leaves the measuring object as mat...

Laser-induced breakdown spectroscopy was investigated already for a broad variety of chemical analytical purposes in the 1970s to 1990s [6.1]–[6.6]. However, a transfer to applications was often prevented because of insufficient analytical performance compared with other atomic emission spectrometric methods such as spark discharge or inductively c...

Among the recent technical developments in Safeguards applications, Laser-Induced Breakdown Spectroscopy (LIBS) provides a promising approach for characterization, analysis and detection of nuclear material. The LIBS method is capable of detecting isotopic signals from U-235 and U-238, therefore allowing enrichment determination of detected uranium...

This book is a comprehensive source of the fundamentals, process parameters, instrumental components and applications of laser-induced breakdown spectroscopy (LIBS). The effect of multiple pulses on material ablation, plasma dynamics and plasma emission is presented. A heuristic plasma modeling allows to simulate complex experimental plasma spectra...

This chapter describes the main process parameters and their influence on LIBS. The effect on the plasma state and the emission spectrum will be described in more detail in Chaps. 4, 6–8.

This chapter describes laser-induced breakdown spectroscopy (LIBS) investigations for the determination of the thickness of coatings or the depth profile of an element in a surface layer.

Laser radiation is a high-quality form of electromagnetic energy enabling a multitude of new methods and applications, such as material processing, biomedical and communication technologies, and measuring methods. The advantages of lasers in measuring technologies are the noncontacting measurement, high flexibility, and high measuring speeds. Due t...

An approach to further increase the sensitivity of LIBS for the determination of traces is the combination of LIBS and laser-induced fluorescence (LIF, also called laser-excited atomic fluorescence spectrometry, LEAFS) [12.1]. Limit of detections for, e.g., heavy metals in soil according to regulatory demands are required to be significantly below...

This chapter describes a selection of industrial applications of LIBS systems based on methodical approaches and instrumental system designs presented in the previous chapters.

In this chapter, investigations are presented to clarify the underlying physical processes of the observed improvements achieved with collinear double pulses studying the space- and time-resolved dynamics of the plasmas generated by laser double pulses interacting with metallic samples, as well as the plasma state in terms of electron density and t...

This chapter describes LIBS investigations for a quantitative bulk analysis of metallic alloys such as steel in solid and liquid state, high-alloy steel, and aluminum. In case of aluminum, the focus is on LIBS analysis of moving Al specimens, which is of interest for inline identification of scrap pieces for material specific recycling (see also cf...

For LIBS of solid samples, the laser radiation evaporates the material and excites spontaneous emission of the material species (cf. Chap. 2). The material is heated locally to boiling or decomposition temperature to achieve an efficient evaporation. The fraction of laser energy absorbed by the material contributes to this process. The amount of te...

This chapter describes LIBS investigations for a bulk characterization or analysis of nonconducting materials, such as polymers, waste electric and electronic equipment, slag, soil, cement, droplets, gases, particulates, and aerosoles.

Quantitative analysis with LIBS is defined here as the determination of concentrations of chemical elements in a specimen. A more generic definition includes as well the application case of material identification where a decision is taken in terms of an allocation of a specimen to a material class by evaluating whether a set of determined concentr...

Various laser types are applied for LIBS and laser ablation studies. The most wide spread are flashlamp-pumped solid-state lasers with Nd:YAG as laser medium operated in the Q-switch mode to generate high-energy laser pulses with pulse durations in the nanosecond range. Table 4.1 gives an overview of the lasers and laser parameters used for LIBS.

This chapter describes LIBS instruments designed for different application fields, the requirements, setup, and performance. The topics chosen for the following sections refer mainly to industrial applications in R&D, inline process control, and quality inspection.

This chapter describes LIBS investigations for a spatially resolved microanalysis of samples using the capability to focus laser radiation to spot sizes below 10μm. Applications of the developed method will be presented in Sect.18.3.

This chapter describes the dominant radiation processes of the laser-generated plasmas such as Bremsstrahlung, recombination radiation, and line radiation. For the line emission being the relevant emission signature used for LIBS, the various line broadening mechanisms are presented and absorption processes are discussed.

A modeling of the emission spectra of laser-induced plasmas for LIBS can contribute to a better understanding of the relevant parameters influencing the observed measuring radiation and potentially be an instrument for a quantitative analysis as well. In a rigorous treatment, such a modeling of the plasma emission should be part of a physical model...

The main objective of this project is to improve the methods for control of metallurgical processes, by introducing online determination of non-metallic inclusion characteristics based on OES-PDA. The work has included method development, software development and several plant trial campaigns. Within the first part of the project, process sampling...

In industrial recycling processes secondary metals need to be separated by material grades before they can be further processed. The identification and separation into different material classes lead to higher value-added industrial feedstock and prevent downgrading processes. Secondary raw materials can be used more efficiently resulting in an inc...

Among the recent technical developments in Safeguards applications, Laser-Induced Breakdown Spectroscopy (LIBS) provides a new approach for characterization, analysis and detection of nuclear material. In this technique sample material is ablated by an intense laser pulse and information on material composition is obtained by spectroscopic analysis...

The dynamics and the structure of the plasma layer in a 1.3 kJ plasma focus were investigated by means of the Schlieren technique. A mode-locked dye laser provides a repetitively pulsed illumination source, which is used for stroboscopic recordings of the plasma sheath. During the rundown phase the plasma layer attains a minimum thickness at a fini...

The Fraunhofer Institute for Laser Technology (ILT) and the Institute of Plastics Processing (1KV) in Aachen, Germany, are collaborating to develop a precise measurement technology for complex multilayer films. The project has been undertaken by them as part of the IRIS project funded by the German ministry of economics and technology (BMWi). The p...

This article is the second part of a two-part series about the history as well as the future of laser technology. In the first part (published in Laser Technik Journal issue 2/2010), the history processes and their perspectives have been discussed as well as the effects on markets and megatrends, thus their societal impact have been displayed. In t...

In emissions originating from industrial processes, elemental concentration characteristically depends on particle size. Therefore, not only is the average chemical composition of the particles in the focus of interest but also their size-dependent composition. For industrial applications such as on-line process control, a system using laser-induce...

An overview of applications of laser-spectroscopy for detection of explosives, food safety and elemental analysis of moving objects for raw material processing and recycling tasks is given. The presentation focuses on Raman, fluorescence and LIBS-spectroscopy. Article not available.

A heuristic model was developed to describe the spectral emission of laser-induced plasmas generated for laser-induced breakdown spectroscopy under the assumption that the composition of the plasma and the plasma state is known. The plasma is described by a stationary spherical shell model surrounded by an ambient gas, which partially absorbs the e...

A significant parameter to monitor the status of concrete buildings like bridges or parking garages is the determination of the depth profile of the chlorine concentration below the exposed concrete surface. This information is required to define the needed volume of restoration for a construction. Conventional methods like wet chemical analysis ar...

Ultraviolet (UV) resonance Raman spectroscopy is a promising technique for the detection of trace explosives. For real-world applications, it is necessary to develop data evaluation algorithms that automatically recognize the spectral features of explosives in a sample spectrum. We have developed a robust algorithm that can tolerate high levels of...

High Power Lasers have been used for years in corresponding applications. Constantly new areas of application and new processes have been demonstrated, developed and transferred to fruitful use in industry and society. In the last years diode pumped solid state lasers in the multi-kW-power regime at beam qualities not far away from the diffraction...

Comparative measurements of Laser-Induced Breakdown Spectroscopy (LIBS) for ultraviolet (UV) and near infrared (NIR) excitation wavelengths on a wide range of plastics and one kind of explosive are presented. The focus of work is on the influence of laser wavelength on the Signal-to-peak to peak noise ratio (SPPNR) for selected emission lines as we...

The aim of this work is to provide a procedure to determine time-resolved electron temperatures with minimized relative errors by the Boltzmann plot method. The applied procedure consists of two parts, a systematic theoretical spectral line selection and an iterative Boltzmann plot algorithm. After a pre-selection of an appropriate non-disturbed or...

Samples taken from the liquid slag layer in a vacuum degasser station of a steel works are analyzed after solidification by laser-induced breakdown spectroscopy (LIBS) without any further sample preparation. The mass fractions of the major components of the vacuum slags are in the range of 50–60% for CaO, 0.5–12% for SiO2 and 20–40% for Al2O3. The...

This paper presents R&D activities to explore new laser parameter ranges in pulse energy, time and space for laser-induced breakdown spectroscopy. The collinear double pulse effect, which is well studied for pulses of typically several 100 mJ energy can also be observed for laser pulses having a pulse energy two orders of magnitude lower. In this c...

Airborne particulate matter in the fine (0.1 µm–2.5 µm) and ultrafine (≤0.1 µm) size range is supposed to affect human health significantly. Smaller particles intrude more deeply into the lungs, so that an organism directly absorbs toxic compounds. Therefore, knowledge of the size-dependent composition of airborne particles is required to determine...

Laser-induced plasmas are investigated during laser micro structuring of a C 75 steel alloy using laser bursts that consist of nanosecond laser pulses under atmospheric pressure. The influence of the laser burst mode — single and collinear double pulses — on plasma dynamics and ablation efficiency is investigated for burst energies in the millijoul...

Geometric quantities of rolled products can be measured online in the manufacturing process using laser measurement technology. Examples of laser inspection systems, which are in routine use in rolling mills, their performance, and the operational experience will be discussed. One to three-dimensional geometric quantities are measured, such as the...

Laser ablation with pulse bursts was studied to increase the ablation rate of steel. Pulse bursts consisting of different numbers of pulses between one and three were used. The microablation with pulses from a multi-pulse Nd:YAG laser with a pulse duration between 20 ns and 60 ns, interpulse separations in the range of 0.1 to 80 μs and burst energi...

The influence of the ambient gas pressure on ablated material and the plasma state of laser-inducedplasmas using single and collinear double pulses is studied. A Q-switchedNd:YAG laser pulse is focused on iron samples in air at pressures ranging from 0.1 to 1013mbar. At 1013mbar double pulses ablate up to a factor of 4.6 more material than single p...

The continuous and simultaneous monitoring of relative concentrations of Na, K, Zn and Pb as well as C, N, O, H, Ca and Fe – being constituents of top gas and dust particles carried therein – is demonstrated by a direct laser measuring in the top gas tube of a blast furnace. The measuring method is laser-induced breakdown spectroscopy (LIBS) which...

LIBS can be used as an online method of characterizing galvanized coatings on sheet steel moving through a production line. The traversing sheet steel is irradiated with a series of single laser bursts, each at a different position on the sheet steel. An ablation depth in the same range as the coating thickness (about 10 microm) is achieved by usin...

In this study a new approach to the online monitoring of the Al depth profile of hot-dip galvanised sheet steel is presented, based on laser-induced breakdown spectroscopy (LIBS). The coating composition is measured by irradiating the traversing sheet steel with a series of single laser bursts, each at a different sheet steel position. An ablation...

The sensitivity of laser-induced breakdown spectroscopy of solid samples depends on the number of ablated and excited analytes. Laser ablation of solid samples can be enhanced by using collinear multiple laser pulses, for example double or triple pulses, rather than single laser pulses with the same total laser pulse energy. The ablation rates and...

The continuous and simultaneous monitoring of relative concentrations of Na, K, Zn and Pb as well as C, N, O, H, Ca and Fe - being constituents of top gas and dust particles carried therein - is demonstrated by a direct laser measuring in the top gas tube of a blast furnace. The measuring method is laser-induced breakdown spectroscopy (LIBS) which...

Laser-spectroscopic methods have a high potential for the remote detection of surface contaminations with residues of explosives, since they can operate contactless, fast and sensitive. Laser-induced breakdown spectroscopy and Raman spectroscopy are two versatile methods which can be employed to identify a wide variety of materials and for which st...

The availability of compact and reliable laser sources, sensitive optical detectors, and powerful computers has helped to stimulate significant growth in industrial applications of LIBS during the past decade. This, together with a better understanding of the physical processes involved when intense laser radiation interacts with a material, has he...

Most of the investigations and applications of LIBS use laser sources operating at repetition frequencies in the range of 10–20 Hz, yielding laser pulse energies of typically 50–300 mJ. This is a consequence of the broad commercial availability of Q-switched flashlamp-pumped solid-state lasers. The most important laser type is the Nd:YAG laser with...

In this study a new method for online analysis of the zinc coating of galvanized sheet steel based on laser-induced breakdown spectroscopy (LIBS) is presented. The coating is characterized with a series of single laser bursts irradiated on the traversing sheet steel, each on a different sheet steel position. To achieve an ablation depth in the rang...

In the last years laser-induced breakdown spectroscopy was introduced in various industrial applications. Automated inspection machines were developed capable to operate under harsh ambient conditions. As an example laser-induced breakdown spectroscopy-based inspection machines for the identification testing of fittings and tubes made of high-alloy...

The miniaturization of analytical techniques is a general trend in speciation analytics. We have developed a new analytical technique combining high pressure liquid chromatography (HPLC) with laser-induced breakdown spectroscopy (LIBS). This enables a molecule-specific separation followed by an element-specific analysis of smallest amounts of compl...

High-alloy steel samples are analysed using laser-induced breakdown spectroscopy (LIBS). A quantitative analysis is carried out for nine elements (Ni, Cr, Cu, Mo, Si, Ti, Mn, Al, C) comparing the influence of single and double pulse excitation and for two different laser burst energies. The laser-induced plasmas are generated with a Nd:YAG laser op...

Spatially resolved information about the distribution and chemical composition of inclusions in steel are gained by scanning methods, such as scanning electron microscopy with energy dispersive X-ray spectroscopy, electron probe microanalysis or capillary-X-ray flourescence. Scanning laser-induced breakdown spectroscopy (LIBS) offers distinct advan...

First published as an Advance Article on the web 3rd March 2004 To control the steel composition during production in steel works, samples are taken from the melt. After solidification, the samples exhibit scale layers of y0.1–1 mm thickness. At present, for analysis of the bulk composition, e.g. by optical emission spectrometry using arc/spark exc...

Significant improvements to the analytical performance of laser-induced breakdown spectrometry (LIBS) were achieved by the use of laser double pulses to ablate and excite the sample material to be analysed. To clarify the underlying physical phenomena the dynamics of the laser-induced plasma in air is studied using a high-speed electro-optic camera...