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As far as Belgium and archaeological window glass is concerned, the most important site is the Dunes Abbey, a former Cistercian abbey near the Flemish coastline. The collection contains approximately 15,000 fragments dating from the 13th to the 16th century. This glass was exposed to atmospheric weathering while in situ for several hundred years, buried for up to 400 years, excavated by different individual excavators in different eras and for over half a century stored in uncontrolled conditions. Moreover, different conservation treatments have been applied to the glass. Due to this, the collection was in a friable condition and we assume half of it has already been completely lost. The remaining collection retains fragments whose condition ranges between almost perfectly preserved material to being completely weathered to the point that no original glass survives. In this research, an important asset is recognizing what has already been lost and maximizing what is still available. During recent conservation and stock making campaigns, the different weathering phenomena were separated into 9 groups based on empirical criteria and detailed registration. As a first step to further investigation of the weathering processes, quantitative SEM-EDX analyses are used to give better insight into the chemical composition of these groups. The aim is to bridge the gap between interpretative archaeologically and archaeological science and to develop a common terminology to evaluate the complexity of weathering phenomena in archaeological window glass collections which can be used as a tool for the assembling and interpretation of these collections.

In this publication optical spectroscopy is considered to be a supplementary technique to study ancient colored glass. It results from a systematic study of th e UV-VIS-NIR transmission spectra of in tentionally colored glass fragments from various archaeological and historical sites and dated from the Roman period to the 21 th century AD. The main goal consists of defining optical sensing parameters for this type of material. The considered colorants are iron, cobalt, manganese, copper and chromium. It is proved that many cases exist wher e optical spectroscopy can be seen as a st raightforward, non-destructive, low-cost and in-situ applicable technique in identifying authentic material or to obtain information about the origin of the material. Possible sensing parameters are defined as the absence/pres ence of absorption bands charact eristic for a specific coloring metal oxide and the spectral position of these bands. These parameters could reveal information about the applied furnace conditions and/or to the composition of the glass matrix. It is shown that the cobalt absorption band situated around 535 nm for soda rich glasses (Roman and industrial times) is shifted towards 526 nm for potash rich glasses (medieval and post-medieval times). Keywords: optical spectroscopy, color, glass, non -destructive testing, chemical analysis, history

Because of the growing demand for healthy and high quality food products many efforts are made to develop new sensing systems for food analysis. In this work we demonstrate the use of a new technique for the detection of stone fragments in fruits, based on the transmission of laser light via scattering. The goal of our research was to develop a technique which could be used for the detection of stone fragments in a broad range of product types in different conditions. We paid special attention to wet products; a product class for which stone identification with the standard X-ray based detection technique is difficult. We studied products with different sizes, textures, internal structures and water contents. In a first part we defined the specifications of the sending side. To detect as much as possible scattered light, the wavelength should not coincide with any absorption line. A literature study about the composition of fruits combined with a study of measured absorption spectra of different products allowed us to select the optimum wavelength. In a next step we performed absorbance measurements and calculated the minimum power of the incident beam applying Beer's law. After the selection of the optimum wavelength and power, we built a proof-of-principle set-up and demonstrated the use of transmission via scattering for the detection of stone fragments in olives, peaches and prunes.

Scanning systems are used in many applications where on-line, high-speed analysis of products is needed. Because of the growing demand for healthy and high quality food products, these systems found their way in several food sensing applications. We will focus on an optical scanning system used for the identification and quality control of vegetables and fruits. It should be able to detect defects as small as 1.5 millimeter and should have a uniform sorting contrast over the entire length of the scanning line. Depending on the application, the analysis process is based on different interaction phenomena such as selective absorption or fluorescence. In this work we first analyzed which parts of the scanning system influence the size of the smallest detectable defect and how the system should be designed in order to fulfill a predefined size. This was done by experimentally analyzing a standard optical scanning system. The major part of our work concentrates on the uniformity of the sorting contrast which depends on the amount of light captured by the detector. We learned that for the standard scanning system this contrast strongly depends on the position of the product in the scanning line. In this paper we highlight the factors which are responsible for this effect and describe a new system characterized by a uniform sorting contrast. The simulations related to this last part were performed with the aid of the optical analysis software ASAP.

In this paper we studied the reflectance spectra of different green vegetables. The main objective was to identify the wavelength(s)(areas) that are the most sensitive to variations in pigment composition. With this we try to meet the ever growing demand from society to classify food products on their quality which is related to the state of ripening and degradation. The group of investigated samples consisted of a group of seven different green vegetables. Because these products have different pigment compositions they formed the ideal test samples for our research. For each product type we measured the reflectance spectra between 400 and 800 nm for 30 samples. From these spectra we investigated three different types of measurands: the measurands that are nowadays commonly used to monitor color differences, the vegetation indices that are defined to monitor plant leaves and measurands that are taking into account the entire reflectance spectrum in the visible part of the electromagnetic spectrum. The main conclusion of our research was that a combination of the first two mentioned types of indices allowed us to identify the different product groups in an optical way.

In this publication we describe the first results of a research project focussed on the use of photonics to solve archaeological problems. We show several examples which prove that absorption spectroscopy can act as a valuable tool to uncover the hidden history behind an excavated glass artefact.

Since the restoration industry in Belgium gets recently more and more involved in the preservation of young (rendered) heritage, it is important to know more about the share of interwar stone imitations in the existing Belgian Building stock. Gaining insight in the present stone imitation typologies and visual properties is an essential step in order to match these materials with an appropriate repair mortar. About 150 façades, situated within the municipality of Etterbeek and finished with stone imitating claddings, were subjected to visual examination. By means of analyzing and comparing close-range photos, and measurements by a spectrocolorimeter (RM 200, X-Rite), a classification was achieved based on the nature of the mortar’s aggregates. Although the initial appearance of these claddings has often changed over time due to different external conditions, the most intact façade areas were compared and finally stored into 17 groups.

In this paper we studied the photosensitivity and scatter properties of several types of photopolymers that are used in the printing industry. We applied different measurement methodologies to experimentally characterize both the absorption and scatter properties of the photopolymers. In a first part we measured the absorption spectra of different unexposed photopolymers in the range between 350 and 1600 nm. From these spectra we calculated the absorbance coefficients. After this, we repeated this procedure for the cured material which we obtained by illuminating the photopolymers with a laser source. We investigated the absorption properties for different illumination times in the range between 0 and 2000 ms. From these measurements we could calculate for the different materials the difference in absorbance between the cured and the non-cured material. Depending on the material the absorbance of the non-cured material was a factor 20 to 60 higher compared to the absorbance of the cured material. These results were used as input for the optical model. In a next step we measured the BTDF for the different materials and calculated the scatter angle at 1/e(2). As a result we obtained scatter angles between 2 degrees and 6 degrees. In a last step we verified and confirmed these differences in scatter behavior by measuring the MTF of a real imaging system that included the photopolymer.

This work describes a rapid sample preparation coupled with independent fluorescence detection for ochratoxin A determination in red wine samples, which has been proven to have the advantages of low solvent consumption, high recovery efficiency and user-friendly operating processes. The validated linear detection range was from 12.5 ppb to 200 ppb with a R2 coefficient of 0.9959. The limit of detection is 50.7 ppb, which needs further optimisation to reach the maximum acceptable limit regulated by European Commission (2 ppb).

Laser cutters and engraving devices traditionally feature a high-power CO2 laser in combination with a scanning unit. However, within the laser processing industry, a growing interest arose in the use and combination of laser diode sources, enabling a more compact design featuring a longer estimated lifespan. Therefore, we investigate and compare different laser diode combination configurations, while evaluating their applicability in a compact laser scanning configuration. Specifically, as a case study, we target the combination of 4 high-power laser diodes, pursuing a collimated, homogenous and symmetrical output beam, while minimizing light losses. An optimal laser diode combination design was achieved by use of aspherical lenses, knife-edge mirrors and a polarizing beam splitter. Two laser diodes are oriented to emit p-polarized light, while the other emit s-polarized light. In front of each laser diode, an aspherical lens is mounted to collect and collimate the laser beam. The two collimated s-polarized laser beams and the two p-polarized beams are each combined using a knife-edge mirror, after which the s- and p-polarized beam are combined by a polarizing beam splitter, giving rise to a single collimated output beam that can be used as input for the scanning unit. Following the optimization and tolerancing of the design, the laser diode combination system was successfully demonstrated in a proof-of-principle laboratory configuration indicating a homogeneous and collimated illumination beam at the entrance of the scan head, paving the way towards the integration and combination of multiple laser diode sources for use in high-power laser cutting and marking applications.

Window glass fragments from four Belgian sites were studied and for a set of eighty-five samples the UV-VIS-NIR transmission spectra were analyzed. This collection contains historical and archaeological finds originating from religious buildings namely the Basilica of Our Lady of Hanswijk in Mechelen (17th-20thc) and the Church of Our Lady in Bruges (16th-20thc) as well as from secular buildings as a private house/Antwerp (18th-1948) and the castle of Middelburg-in-Flanders (1448-17thc). All sites contain material on the hinge point between the medieval and the industrial tradition. The variation in composition of the analyzed samples can be explained by the use of different glassmaking recipes, more specifically the use of different raw materials. The composition of window glass differs essentially in the type of flux, using a potash rich fluxing agent until the post-medieval times and industrial soda from the 19th century onwards. A second difference concerns the iron impurities in the glass. For all fragments a clear compositional classification could be made based on the iron concentration. These conclusions were based on archaeological research and drawn after submitting samples to expensive, complex, time-consuming and destructive chemical analyzing methods. Our study indicates that similar conclusions could be made applying the proposed optical based methodology for plain window glass. As a whole, the obtained results make it possible to cluster the fragments for a particular site based on three different sensing parameters: the UV absorption edge, the color and the presence of characteristic absorption bands. This information helps in identifying trends to date window glass collections and indicating the use of different raw materials, production technologies and/or provenance.

Archaeometric research on glass artefacts is continuously evolving and is converging towards a multidisciplinary research domain where different types of techniques are applied depending on the questions asked and the circumstances involved. The technique described in this work is optical spectroscopy. The benefit of this technique being the possibility of building up a knowledge database for a large amount of material in a relatively short period of time and with a relatively limited budget. This is of particular interest for the investigation of extensive and/or unexplored glass collections where a first-line analysis of artefacts could facilitate the selection of material needing further and more detailed examination. This publication explores the extent to which optical spectroscopy can be used for a first-line analysis of green coloured glass artefacts from the Roman period. It is shown that the colour coordinates calculated from the measured transmission spectrum could reveal information about the fragment under study. In particular it is shown that 1) based on the position of the calculated colour values on the colour diagram (CIE1931) one could easily know whether the artefact was coloured using only iron or if copper oxides were also present. In the case of the artefact owing its colour solely to the presence of iron, the distance between the measured colour values and the colour diagram's white point can roughly indicate the iron concentration of the sample; 2) artefacts that were fabricated under similar furnace conditions can also be identified on the colour diagram; 3) samples with identical compositions and fabrication conditions but with different sample thickness, gave rise to a variation in the colour coordinates, thus allowing optical spectroscopy to help identify fragments which might belong to the same object. (C) 2011 Elsevier Ltd. All rights reserved.

This paper is the first part in a series of three where the authors show how photonics based food sensors can contribute to the quality control and safety of solid and liquid food products. In this first part, we describe the theoretical aspects of the various physical phenomena that can occur during food screening together with their related measurement setups. In addition, this document contains information regarding data processing and the concerned sensing platforms.

Plenty of research has been performed to quantify microplastics in bottled water. To achieve a standardized method for microplastics isolation, general practices for microplastics analysis have been proposed to ensure reliable results, such as optimized sample volume, guidelines to prevent sample contamination, and methods to count and identify the microplastics isolated. An adequate sample volume is a relevant parameter as the microplastics concentration per size range varies with it, being higher for small particles (300µm). Therefore, a representative volume of the sample is needed to estimate correctly the content of particles. In this work, an isolation methodology of fractionated filtration is implemented for bottled water processing to ease the processing of larger sample volumes and reduce sample contamination by limiting the contact of the sample with the environment during the filtration. The experimental process compares the performance of the traditional fractionated filtration in sequential filtrations to the method proposed. The process consists of 4 sequential filtrations with each method: 3 replicates and one blank. In each filtration, 10 liters of bottled water, from the same brand and batch, were filtered through 3 filters in sequence with pore sizes of 10µm, 5µm, and 1µm. Later the samples were processed chemically to remove any organic matter. The microplastics collected were mixed with filtered alcohol, deposited on ZnSe windows, and analyzed with a µFTIR spectrometer. Additionally, the proposed method performs a separation of microplastics by size which enables the identification with a different analytical method per size range (FTIR for larger particles¿10µm and Raman for smaller ones Also see: https://micro2022.sciencesconf.org/427117/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

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Carcinogenic and toxic contaminants in food and feed products are nowadays mostly detected by destructive, time-consuming chemical analyses, like HPLC and LC-MS/MS methods. However, as a consequence of the severe and growing regulations on food products by the European Union, there arose an increased demand for the ultra-fast, high-sensitive and non-destructive detection of contaminants in food and feed products. Therefore, we have investigated fluorescence spectroscopy for the characterization of carcinogenic aflatoxins. With the use of a tunable titanium-sapphire laser in combination with second and third harmonic wavelength generation, both one- and two-photon induced fluorescence excitation wavelengths could be generated using the same setup. We characterized and compared the one- and two-photon induced fluorescence spectra of pure aflatoxin powder, after excitation with 365nm and 730nm respectively. Moreover, we investigated the absolute fluorescence intensity as function of the excitation power density. Afterwards, we applied our characterization setup to the detection of aflatoxins in maize grains. The fluorescence spectra of both healthy and contaminated maize samples were experimentally characterized. In addition to the fluorescence spectrum of the pure aflatoxin, we observed an unwanted influence of the intrinsic fluorescence of the maize. Depending on the excitation wavelength, a varying contrast between the fluorescence spectra of the healthy and contaminated samples was obtained. After a comparison of the measured fluorescence signals, a detection criterion for the optical identification of the contaminated maize samples could be defined. As a result, this illustrates the use of fluorescence spectroscopy as a valuable tool for the non-destructive, real-time and high-sensitive detection of aflatoxins in maize.

In this work we summarize some of the results we obtained during our research of different physical phenomena which take place when a visible or near-infrared laser beam falls in onto a biological product, more in particular on a vegetable or on a fruit. The most important phenomena are surface reflection, selective absorption, fluorescence, absorption in the near-infrared and internal reflection. While the emphasis lays on the identification of the product type we will show that some of the demonstrated sorting principles can also be used for quality sorting: for example a determination of the ripeness of green vegetables or of the water/oil content of vegetables and fruits and a detection of the presence of the very harmful aflatoxines.

In this paper we have studied by optical spectroscopy the 5th–7th century glass material from three early Christian sites in Cyprus: Yeroskipou, Maroni Petrera and Kalavasos Kopetra. The glasses could be grouped into six chemical types: Levantine 1, HLIMT, two types of HIMT (named HIMTa and HIMTb), Egypt 1 and HIT. This work presents the first extensive application of in situ absorption spectroscopy to ancient glasses. UV absorption edge, Fe2 + concentration and colour coordinates are optical parameters that help identifying glass composition because there exists a link between chemical groups and UV–vis–NIR spectral shapes. This allows to select samples for chemical analysis on the basis of diverging optical properties rather than using ad random or subjective naked-eye strategies groups. Furthermore, optical spectroscopy offers an insight into the redox conditions under which the glasses were melted. We also show why the common practice among glass archaeologists to associate certain colour to specific chemical compositions can lead to misinterpretation of the glass consumption.

In this work we describe the design of a confocal microscope based optical system which can be used for two types of miniaturized fluid-chromatographic experiments: first of all for the study of shear-driven fluid separations in microchannels and secondly for the study of peak-broadening phenomena in pressure-driven fluids in the same type of microchannels. For the first type of measurements fluorescing dyes (coumarins) are used while for the latter type photo-active molecules (uncaged dyes) like for example fluorescein molecules are needed. We designed the detection system in such a way that by making some small changes to the system we can swap from one application to the other. After calculating the specifications of the optical components, we simulated the system with the sequential ray-tracing-software Solstis and built the system. Finally we did some preliminary experiments which demonstrated the working principle of our setup.

In the past few years, intensive research efforts have been devoted to studying new approaches to controlling the photon emission of quantum emitters (QEs), especially for telecommunication applications. These approaches rely on tailoring the QE\'s radiation, usually assessed via well-known figures-of-merit such as lifetime (τ) and quantum efficiency (η). Controlling the QE\'s photon emission is important because the faster its photons are emitted, the greater is the number of times it returns to the excited state per second. Therefore, it is crucial to create additional decay channels to reduce τ, which necessarily requires increasing the Purcell factor (P). One of the most promising approaches to increase P involves a new class of metamaterials, known as hyperbolic metamaterials (HMM). This class of materials exhibits pronounced anisotropy, with the parallel and perpendicular permittivity tensor elements (with respect to the anisotropy axis) presenting opposite signs, resulting in an open hyperboloidal isofrequency surface (IS). This unusual IS shape leads to the most outstanding feature of HMMs, namely, the existence of photonic modes with wavenumber (k) much larger than those in free-space (k0), known as high-k modes. By engineering these modes, it is possible to manipulate the HMM photonic density of states (PDoS), thus controlling the QE\'s radiation parameters. The simplest approach to designing HMM is by means of a planar stack of alternating thin metal and dielectric layers. However, the finite thickness of these layers induces spatial dispersion, making the extraction of effective parameters (homogenization) of these media a challenging task. In this context, we propose in this thesis a new constitutive parameter retrieval approach that takes spatial dispersion into account for all electromagnetic parameters of the medium. We demonstrate that the real part of the dispersion curve flattens out (correspondingly with a large imaginary part) because of the absence of propagating modes inside the metamaterial. This flat region is strongly dependent on the layer thicknesses and is a direct manifestation of spatial dispersion. Moreover, we demonstrate that the QE\'s lifetime calculation is overestimated if this effect is not taken into account in the homogenization procedure, which is detrimental for telecommunication applications. Moreover, we demonstrate how to enhance P by a factor greater than 100 with the use of HMMs. However, most of the QE dissipated power couples into the HMM as high-k modes (which do not propagate in free-space). Therefore, the energy is thermally dissipated inside the HMM with a consequent reduction of η . Some authors have resorted to nano-patterned HMMs (NPHM) to convert the high-k modes into free-space modes (k≤k0) aiming at increasing η. However, much of the NPHMs designs still rely on computationally costly three dimensional (3D) numerical simulations. Thus, we also propose in this thesis a new semi-analytical method to model, both in two- and three-dimensions (2D and 3D, respectively), the radiation emission of QEs interacting with nano-patterned structures. The low computational cost of this method makes it attractive for mapping P and η as function of the QE and NPHM relative position. This mapping is a helpful tool to understand the decay behavior of the whole system since QEs are arbitrarily distributed and oriented inside the NPHM. The analytically calculated decay curve allows the systems effective quantum efficiency (ηeff) and Purcell factor (Peff) to be directly obtained assuming multiple arbitrarily distributed electromagnetic sources. In this sense, we propose here a new procedure to optimize the NPHM geometrical parameters to maximize ηeff while achieving the desired Peff. We apply the proposed model to an NPHM composed of nine Ag/SiO2 layers, with the polymer host layer embedded with Rhodamine 6G, to maximize ηeff for a specified tenfold increase of Peff. This procedure allowed ηeff to be increased by 69% and 170% for one- and two-dimensional nano-patterning, respectively. Moreover, the time required to build the P and η maps (used in the calculation of the decay behavior) is reduced by approximately 96% when compared to those numerically calculated via FDTD. This procedure paves the way to the realization of new high-speed and efficient light sources for telecommunication applications. Nos últimos anos, intensivo esforço tem sido devotado para o estudo de novas método para o controla da missão de fótons de emissores quânticos (EQs), especialmente para aplicações em telecomunicações. Estes métodos dependem da adaptação da radiação dos EQs, geralmente avaliadas por meio das bem conhecidas figuras de mérito, como o tempo de meia vida (τ) e a eficiência quântica (η). O controle da emissão de fótons é importante pois quanto mais rápido os fótons são emitidos, maior é o número de vezes que o EQ retorna ao seu estado excitado por segundo. Portanto, é crucial criar canais de decaimento adicionais para reduzir τ, o que necessariamente requer o aumento do fator de Purcell (P). Uma das abordagens mais promissoras para aumentar P envolve uma nova classe de metamateriais, conhecida como metamateriais hiperbólicos (MHs). Esta classe de materiais apresenta pronunciada anisotropia, onde os elementos paralelo e perpendicular do tensor de permissividade (em relação ao eixo de anisotropia) apresentam sinais opostos, resultando em uma superfície de isofrequência (SI) hiperboloidal aberta (IS). Essa forma incomum de SI leva à característica mais marcante dos MHs, a existência de modos fotônicos com número de onda (k) muito maior do que aqueles no espaço livre (k0), conhecidos como modos alto-k. Ao manipular esses modos, é possível manipular a densidade de estados fotônicos (DES) dos MHs, controlando assim os parâmetros de radiação do QE. A abordagem mais simples para a criação de MHs é por meio de uma pilha plana de camadas metálicas e dielétricas alternadas. Entretanto, a espessura finita dessas camadas induz a dispersão espacial, tornando a extração de parâmetros efetivos (homogeneização) destes meios uma tarefa desafiadora. Neste contexto, propomos nesta tese uma nova abordagem de recuperação de parâmetros constitutivos a dispersão espacial de todos os parâmetros eletromagnéticos do meio é levada em consideração. Nós demonstramos que a parte real da curva de dispersão se aplaina (correspondentemente com uma grande parte imaginária) devido à ausência de modos propagantes dentro do metamaterial. Esta região plana é fortemente dependente das espessuras das camadas e é uma manifestação direta da dispersão espacial Além disso, nós mostramos que se a dispersão espacial não for corretamente considerada no processo de homogeneização, o tempo de meia vida do EQ pode ser superestimado, o que é prejudicial para aplicações de telecomunicações. Além disso, demonstramos como melhorar P por um fator maior que 100 com o uso de MHs. a maior parte da potência dissipada pelos EQs são acopladas nos MHs como modos de alto-k (que não se propagam no espaço livre). Portanto, a energia é dissipada termicamente no interior do MH, resultando em uma redução de η. Alguns autores recorreram a MHs nano-estruturados (MHNE) para converter os modos alto-k em modos de espaço livre (k≤k0) visando o aumento de η. No entanto, muitos dos projetos do NPHM ainda dependem de simulações numéricas tridimensionais (3D) computacionalmente dispendiosas. Assim, também propomos nesta tese um novo método semi-analítico para modelar, tanto em duas como em três dimensões (2D e 3D, respectivamente), a emissão de radiação de EQs interagindo com estruturas nano-estruturadas. O baixo custo computacional deste método faz com que seja atrativo para o mapeamento de P e η em função da posição relativa do EQ e do MHNE. Esse mapeamento é uma ferramenta útil para entender o comportamento de decaimento de todo o sistema, já que os EQs são arbitrariamente distribuídos e orientados dentro do MHNE. A curva de decaimento calculada analiticamente permite que a eficiência quântica efetiva do sistema (ηeff) e o fator de Purcell (Peff) sejam obtidos diretamente, assumindo múltiplas fontes eletromagnéticas arbitrariamente distribuídas. Neste sentido, propomos aqui um novo procedimento para otimizar os parâmetros geométricos do MHNE visando a maximização de ηeff enquanto Peff é aumentado à um valor desejado. Aplicamos o modelo proposto a um MHNE composto por nove camadas de Ag/SiO2, com a camada de polímero embutida com Rodamina 6G, visando maximizar ηeff para um aumento de dez vezes de Peff. Este procedimento permitiu que o ηeff fosse incrementado em 69% e 170% para nano-estruturas uni e bidimensionais, respectivamente. Além disso, o tempo necessário para construir os mapas P e η (utilizados no cálculo da curva de decaimento) é reduzido em aproximadamente 96% quando comparado com os calculados numericamente via FDTD. Este procedimento abre caminho para o desenvolvimento de novas fontes de luz de alta velocidade e eficiência para aplicações de telecomunicações.