Le marché des diodes électroluminescentes (LEDs) de puissance est en perpétuelle croissance depuis une vingtaine d’années. Le marché de l’éclairage évolue car les besoins ont changé : nous souhaitons, par exemple, aujourd’hui réduire la consommation électrique, ou avoir des éclairages plus flexibles (couleur, cycle d’allumage, encombrement, …). Les LEDs de puissance permettent d’apporter des solutions où les autres éclairages font défauts. Une étude comparative est menée entre les LEDs et les autres sources d’éclairages. Une LED de puissance émettant une lumière blanche est constituée d’une puce semi-conductrice, d’un substrat, d’un PAD et d’une optique primaire. Différentes méthodes permettent d’obtenir de la lumière blanche avec des LEDs : plusieurs puces, une puce avec un ou des luminophores, ou la méthode PRS-LED. Le luminophore a un rôle optique important et un rôle thermique non négligeable. Après avoir été excité par la lumière émise de la puce, il réémet de la lumière dans une longueur d’onde supérieure. L’efficacité de ce processus dépend de nombreux paramètres, comme la mise en oeuvre du luminophore ou le type de luminophore utilisé. L’étude et la caractérisation des propriétés optiques et thermiques sont faites pour des LEDs commerciales, composées d’une même puce émettant de la lumière bleue, avec et sans luminophore jaune. Afin de maitriser le maximum de facteurs, nous avons mené une étude et un dimensionnement du circuit imprimé (PCB) sur lequel va être implanté nos LEDs. Dans le but d’évaluer les matériaux constituant les LEDs, des analyses au microscope à balayage électronique et par microsonde ont été menées. Ces travaux ont permis de révéler, notamment, la position de la jonction p-n dans la puce et la composition de la couche de luminophore par deux types différents. De plus, afin d’améliorer notre compréhension, une étude comparative a été menée sur trois luminophores jaunes. Ensuite, les deux types de LEDs, puce nue et puce avec luminophore, ont été testés dans le but d’obtenir le flux lumineux et le rendement des LEDs. La caractérisation optique nous a amené à créer un banc pour obtenir la luminance énergétique spectrale sur une partie minime de la puce. D’autre part, nous nous intéressons à la température de jonction de la puce nue, que nous mesurons par différentes méthodes, dont la thermographie infrarouge. Pour cela, l’émissivité a été estimée pour la puce nue et la puce avec luminophore. Puis nous comparons aussi ces différentes méthodes pour le calcul de la résistance thermique Rth j-PAD entre la jonction et le PAD. Le maillage de fils conducteurs implanté sur la surface de la puce est modélisé électriquement. Cette étude, qui est composée de niveaux progressifs de modélisation, permet de comprendre la répartition du courant électrique qui traverse la jonction, et ainsi d’appréhender la répartition du flux lumineux et de la température au niveau de la surface de la puce. Après, un modèle thermo-optique décrit les phénomènes présents au niveau de la jonction d’une puce nue : la conversion de la puissance électrique en lumière bleue et en chaleur, et les transferts de chaleur. Nous complétons ce premier modèle pour obtenir un modèle d’une puce avec le luminophore. Ce dernier modèle prend en compte la photo-conversion du luminophore avec le calcul de flux lumineux à la sortie du luminophore et le calcul de la chaleur due à la photo-conversion. La résolution de ce modèle nous permet d’obtenir la température de jonction d’une puce avec luminophore. La conservation d’énergie du modèle est aussi vérifiée. Le modèle thermo-optique est appliqué à une cartographie de température de surface afin d’obtenir une cartographie de la température de jonction. Ces cartographies sont regroupées avec les clichés de thermographie infrarouge et de luminance énergétique. / The high brightness LED market is constantly growing last twenty years. The lighting market is changing as needs have changed: we would like, for example, reduce power consumption, or have more flexible lighting (color, lighting cycle, dimensions ...). High brightness LEDs help provide solutions where others are lighting defects. A comparative study is conducted between the LEDs and other lighting sources.The operation of a high brightness LED emitting white light is explained with the description of each element: chip, substrate, the PAD and optics. Then the different methods of obtaining white light with LEDs are compared: several chips, a chip with one or more phosphors, or PRS-LED method. The phosphor has a significant optical role and an important thermal role. After being excited by the light emitted from the chip, it re-emits light in a greater wavelength. The effectiveness of this process depends on many parameters, such as the implementation of the phosphor, or the type of phosphor used. The study and characterization of optical and thermal properties are made for commercial LEDs, composed of a single chip emitting blue light with and without yellow phosphor. To master the maximum factors, we conducted a study and design of the printed circuit board (PCB) on which will be implanted our LEDs. In order to evaluate the materials constituting the LEDs, analyzes made at scanning electron microscope, and by microprobe were conducted. This work has revealed in particular the position of the p-n junction in the chip, and the composition of the phosphor layer of two different types. Moreover, to improve our understanding, a comparative study will be conducted on three yellow phosphors. Then the two types of LEDs, bare chip and chip with phosphor, were tested in order to obtain the luminous flux and efficiency of LEDs. The optical characterization has led us to create a bench for spectral radiance over a small portion of the chip. Furthermore, we are interested in the junction temperature of the bare chip, which we measure by various methods, including infrared thermography. For this, the emissivity was estimated for the bare chip and the chip with phosphor. Then we also compare these different methods to calculate the thermal resistance Rth j-PAD between the junction and the PAD. The mesh of conductive wires, implanted on the surface of the chip, is electrically modeled. The study, which is composed of three progressive levels of modeling, provides an understanding of distribution of the electric current through the junction, and thus to understand the distribution of the light flow and temperature at the surface of the chip. Afterwards, an optical-thermal model describes the phenomena present at the junction of a bare chip: converting electrical power into blue light and heat, and heat transfer. We complete this first model for a model of a chip with the phosphor. This model takes into account the photo-conversion of the phosphor with the calculation of the luminous flux at the output of the phosphor and the calculation of the heat due to the photo-conversion. The resolution of this model allows us to obtain the junction temperature of a chip with phosphor. The model of energy conservation is also verified. The optical-thermal model is applied to a surface temperature mapping in order to obtain a mapping of the junction temperature. These maps are combined with pictures of infrared thermography and radiance.

<p>Over the last two decades, an increasing number of highway construction and maintenance projects in the United States have been completed at night to avoid or mitigate traffic congestion delays. Working at night entails several advantages, including lower traffic volumes at night, reduced impact on local businesses, more freedom for lane closures, longer possible work hours, lower pollution, cooler temperatures for equipment and material, and fewer overall crashes due to lower traffic volumes at night. Although nighttime roadway operations may minimize traffic disruptions, there are several safety concerns for motorists passing by and for workers in the nighttime work zone. For instance, just in 2019, there were 842 work zone fatalities reported in the United States, with 48% of these being associated with fatalities on night shifts. Additionally, 70% of these fatalities involved drivers/occupants under the age of 50. Moreover, improper lighting arrangements or excessive lighting levels produced by temporary lighting systems installed at the job site could cause harmful levels of glare for the traveling public and workers leading to an increase level of hazards and crashes in the vicinity of the work zone. </p> <p>To address the issue of glare, very few studies have been conducted to evaluate and quantify glare at work zones. Most of these studies were limited to the determination of disability glare levels of lighting systems (balloon lights and light towers) with a metal-halide type light source by using the veiling luminance ratio (<em>VL ratio</em>) as a criterion for limiting disability glare. However, deeper evaluation of the effects of driver’s age on the veiling luminance ratio, and the use of energy-efficient lighting systems which employ light-emitting diode (LED) type light sources were not performed.</p> <p>This thesis focuses on determining and evaluating disability glare on nighttime work zones as a step towards developing appropriate lighting strategies for improving the safety of workers and motorists during nighttime highway construction and maintenance projects. Disability glare is the glare that impairs our vision of objects without necessarily causing discomfort and it can be evaluated using the veiling luminance ratio (<em>VL ratio</em>). In this study, disability glare values were determined by using lighting data (vertical illuminance and pavement luminance measurements) from testing 49 lighting arrangements. Two LED balloon lights, a metal-halide light tower, and an LED light tower were utilized for the field lighting experiments. The disability glare level evaluation examines the effects of mounting height, power output, rotation angle, and aiming angle of luminaires on the veiling luminance ratio values (which is a criterion for limiting disability glare). </p> <p>The analysis of the disability glare values revealed four major findings regarding the roles played by the mounting height, power output, lighting system orientation, aiming angles of luminaries, and driver’s age on disability glare levels as follows: (i) an increase in mounting heights of both balloon lights and light towers resulted in lower veiling luminance ratio values (or disability glare); (ii) compared to the "perpendicular" and "away" orientations, orienting the light towers in a "towards" direction (45 degrees) significantly increases the disability glare levels of the lighting arrangement; (iii) increasing the tilt angles of luminaires of the portable light towers resulted in an increase in veiling luminance ratio values; (iv) for balloon lights, at observers ages over 50, <em>VL ratio</em> values were found to be greater than the maximum recommended; (v) for LED light towers oriented towards the traffic, at driver’s ages over 40, <em>VL ratio</em> values exceed the Illuminating Engineering Society (IES) recommended value; and (vi) for metal-halide light towers oriented towards the traffic, at driver’s ages over 50, <em>VL ratio</em> values exceed the IES recommended value. The results from this research study can provide State Transportation Agencies (STAs) and roadway contractors with a means to improve glare control strategies for nighttime work.</p>

No description available.

In this study, the design and fabrication of a monolithic InP-based 1550-nm photonic-crystal surfaceemitting laser (PCSEL) is reported. The device is composed by an InGaAsP multi-quantum well (MQW) active layer and InP photonic crystal (PhC) formed by metal organic chemical vapour deposition (MOCVD). A theoretical study based mainly on the Fourier modal method using Stanford Stratified Structure Solver (S 4) and finite element analysis using COMSOL Multiphysics was carried out in order to optimize the emission at 1550 nm due to the two-dimensional band-edge resonance effect at the Γ point.The device design and modeling, materials testing (annealing and MOCVD regrowth), process optimization and the fabrication of light emitting diodes (LEDs) based on the same structure as the PCSELs (without the PhC) is reported. The fabricated devices show a low series resistance of 8.19 Ω and a turn-on voltage of 0.84 V. The average differential output power is 41 mW/A with an electroluminescent peak at 1511 nm. The full assembly of the final PCSEL devices is beyond the scope of the present thesis and corresponds to an ongoing project expected to be finalized within the coming year. However, detailed guidelines and fabrication instructions, including the manufacturing of an appropriate lithographic mask set, are provided. / Föreliggande examensarbete rapporterar designen och tillverkningsprocessen för en monolitisk InPbaserad 1550-nm så kallad Photonic-Crystal Surface-Emitting Laser (PCSEL). Komponenten bestå r av en aktiv kvantbrunnsstruktur i InGaAsP och ett fotoniskt-kristall (PhC)-lager i InP, bägge odlade med hjälp av metalorganisk gasfasepitaxi (MOCVD). En teoretisk studie baserad på Fourier-modalmetoden med användning av Stanford Stratified Structure Solver (S4) och finit elementanalys-metoden med med hjälp av av COMSOL Multiphysics utfördes för att optimera emissionen vid 1550 nm genom en tvådimensionell bandkantsresonanseffekt vid Γ punkten.Rapporten går igenom komponentdesign och modellering, materialtestning (värmebehandling och MOCVDåterväxt), processoptimering och tillverkning av lysdioder (LED) baserade på samma struktur som PCSELkomponenterna (men utan PhC-strukturering). De tillverkade lysdioderna uppvisar en låg serieresistans på 8.19 Ω och en framspänning på 0.84 V. Den genomsnittliga differentiella utgångseffekten är 41 mW/A med en luminescenstopp vid 1511 nm. Den slutliga tillverkningen av färdiga PCSEL-enheter ligger utanför ramen för detta examensarbete och motsvarar istället ett pågående projekt som förväntas bli slutfört inom det kommande året. Däremot ges detaljerade riktlinjer och tillverkningsinstruktioner, för vilket ett fotolitografiskt mask-set även tagits fram.

Gallium nitride (GaN) light emitting diodes (LED) embody a large field of research that aims to replace inefficient, conventional light sources with LEDs that have lower power, higher luminosity, and longer lifetime. This thesis presents an international collaboration effort between the State Key Laboratory for Mesoscopic Physics in Peking University (PKU) of Beijing, China and the Electrical Engineering Department of California Polytechnic State University, San Luis Obispo. Over the course of 2 years, Cal Poly’s side has simulated GaN LEDs within the pure blue wavelength spectrum (460nm), focusing specifically on the effects of reflection gratings, transmission gratings, top and bottom gratings, error gratings, 3-fold symmetric photonic crystal, and 2-fold symmetric nano-imprinted gratings. PKU used our simulation results to fabricate GaN high brightness LEDs from the results of our simulation models. We employed the use of the finite difference time domain (FDTD) method, a computational electromagnetic solution to Maxwell’s equations, to measure light extraction efficiency improvements of the various grating structures. Since the FDTD method was based on the differential form of Maxwell’s equations, it arbitrarily simulated complex grating structures of varying shapes and sizes, as well as the reflection, diffraction, and dispersion of propagating light throughout the device. We presented the optimized case, as well as the optimization trend for each of the single grating structures within a range of simulation parameters on the micron scale and find that single grating structures, on average, doubled the light extraction efficiency of GaN LEDs. Photonic crystal grating research in the micron scale suggested that transmission gratings benefit most when grating cells tightly pack together, while reflection gratings benefit when grating cells space further apart. The total number of grating cells fabricated on a reflection grating layer still affects light extraction efficiency. For the top and bottom grating structures, we performed a partial optimization of the grating sets formed from the optimized single grating cases and found that the direct pairing of optimized single grating structures decreases overall light extraction efficiency. However, through a partial optimization procedure, top and bottom grating designs could improve light extraction efficiency by 118% for that particular case, outperforming either of the single top or bottom grating cases alone. Our research then explored the effects of periodic, positional perturbation in grating designs and found that at a 10-15% randomization factor, light extraction efficiency could improve up to 230% from the original top and bottom grating case. Next, in an experiment with PKU, we mounted a 2-fold symmetric photonic crystal onto a PDMS hemi-cylinder by nano-imprinting to measure the transmission of light at angles from near tangential to normal. Overall transmission of light compared with the non-grating design increases overall light extraction efficiency when integrated over the range of angles. Finally, our research focused on the 3-fold symmetric photonic crystal grating structure and employed the use of 3-D FDTD methods and incoherent light sources to better study the effects of higher-ordered symmetry in grating design. Grating cells were discovered as the source of escaping light from the GaN LED model. The model revealed that light extraction efficiency and the far-field diffraction pattern could be estimated by the position of grating cells in the grating design.

Light has a wide and profound non-visual impact on the human body. It is related to the suppression or synthesis of a hormone called melatonin which regulates the human circadian clock. In Nordic countries like Sweden, lack of natural light in winter may lead to negative health effects such as circadian disorders or depression. At the same time, the underground metro system in Stockholm carries more than one million passengers on a weekday. The lighting in the train carriage may have distinct circadian effects on the passengers. The paper takes the metro system in Stockholm as an example, calculates the non-visual effects of the artificial lighting in the train according to Equivalent Melanopic Lux (EML), Circadian Stimulus (CS) and Melanopic Equivalent Daylight Illuminance (M-EDI) Models, compares with current guidance and suggestions, considers the daylighting conditions of Stockholm, and proposes a new design solution with adjustable LEDs to achieve a better healthful circadian lighting result.

Integration of optical wireless communications (OWC) within switched-mode power supplies (SMPS) / Although visible light communication(VLC) systems can provide high density links for use with IoT devices, an energy efficient, high rate method of designing a VLC transmitter is still unclear. Present designs for transmitters such as the bias-T, designs with switch manipulation, and interleaved converters are not commercially viable due to costly and complex designs that sacrifice energy efficiency for data rate. A design allowing for efficient, high rate communications, while maintaining a low cost would allow for widespread adoption of this technology. In this thesis, a novel approach of integrating power converters and VLC systems is explored by replacing commutating diodes with LEDs. By leveraging switched-mode power supply(SMPS) structures, the power dissipated within the converter may be harnessed and used for communications. The result is a simple and energy efficient solution capable of high rate links. Simulation and experimental results demonstrate buck and boost SMPS topologies that simultaneously increase energy efficiency and provide communications at SMPS switching rate without increasing component count. / Thesis / Master of Applied Science (MASc)

On demand single-photon and entangled-photon sources are key building-blocks for many proposed photonic quantum technologies. For practical device applications, epitaxially grown quantum dots (QDs) are of increasing importance due to their bright photon emission with sharp line width. Particularly, they are solid-state systems and can be easily embedded within a light-emitting diode (LED) to achieve electrically driven sources. Therefore, one would expect a full-fledged optoelectronic quantum network that is running on macroscopically separated, QD-based single- and entangled-photon devices. An all-electrically operated wavelength-tunable on demand single-photon source (SPS) is demonstrated first. The device consists of a LED in the form of self-assembled InGaAs QDs containing nanomembrane integrated onto a piezoelectric crystal. Triggered single photons are generated via injection of ultra-short electrical pulses into the diode, while their energy can be precisely tuned over a broad range of about 4.8 meV by varying the voltage applied to the piezoelectric crystal. High speed operation of this single-photon emitting diode up to 0.8 GHz is demonstrated. In the second part of this thesis, a fast strain-tunable entangled-light-emitting diode (ELED) is demonstrated. It has been shown that the fine structure splitting of the exciton can be effectively overcome by employing a specific anisotropic strain field. By injecting ultra-fast electrical pulses to the diode, electrically triggered entangled-photon emission with high degree of entanglement is successfully realized. A statistical investigation reveals that more than 30% of the QDs in the strain-tunable quantum LED emit polarization-entangled photon-pairs with entanglement-fidelities up to f+ = 0.83(5). Driven at the highest operation speed ever reported so far (400 MHz), the strain-tunable quantum LED emerges as unique devices for high-data rate entangled-photon applications. In the end of this thesis, on demand and wavelength-tunable LH single-photon emission from strain engineered GaAs QDs is demonstrated. Fourier-transform spectroscopy is performed, from which the coherence time of the LH single-photon emission is studied. It is envisioned that this new type of LH exciton-based SPS can be applied to realize an all-semiconductor based quantum interface in the foreseeable distributed quantum networks.

La thèse intitulée «Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” eststructurée en cinq chapitres traitant de nouveaux: a)cyclopenta[c]pyrannes hétérocyclique; b)des propriétés fluorescentes; d) potentiels dispositifs de l'électroniquemoléculaire; d) donneurs moléculaires pour les photovoltaïquesorganiques et e) carbon‘quantum’dots électroluminescents.Le premier chapitre présente une étude des dérivéspseudoazulenique ayant une unité cyclopenta[porte sur leur synthèse, l'analyse structurale et leur comportement dansdes réactions de substitution électrophile pour obtenir des composésayant des propriétés fluorescentes.Le deuxième chapitre présentediastéréoisomères et l'étude de propriétés de fluorescencedérivés d’indenopyrone.Le troisième chapitre décrit la synthèse des nouvellesarchitectures basées sur l’unité cyclopenta[être modifiés structurellement par l'influence d'un stimulus chimiqueou électrochimique afin d'élaborer des potentiels dispositifs del'électronique moléculaire.Dans le quatrième chapitre, la synthèsedes propriétés électroniques des nouvelles molécucellules solaires organiques (OSC) ontLe cinquième et dernier chapitre décrit la passivation desdéfauts de surface des nanoparticules de carbone avec desmolécules organiques ou des polymères pour obtenir desnanoparticules de carbone photoluminescentse surnommé ‘quantum dots. / The thesis entitled “Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” isstructured into five chapters concerning new: a) heterocycliccyclopenta[c]pyrans; b) indenopyrone derivatives with fluorescentproperties; c) potential devices of molecular electronics; d)donors for organic photovoltaics and e) electroluminescent carbon‘quantum’ dots.The first chapter presents a study of pseudoazulenederivatives having a cyclopenta[c]pyran unit. The survey comprises thesynthesis, structural analysis and reactivity towards electrophilicsubstitution in order to obtain fluorescent compounds.The second chapter deals with the separation odiastereoisomers and the study of fluorescent propertiesindenopyrone derivatives.The third chapter describes the synthesis of newarchitectures based on cyclopenta[c]pyran unit that can be structurallymodified by the influence of a chemical or electrochemical stimulus inorder to work as potential devices in molecular electronics.In the fourth chapter, the synthesis andelectronic properties of new molecular donors for organic solar cellswas described.The fifth and last chapter outlines the passivation of surfacedefects on carbon nanoparticles using small organic molecules orpolymers in order to obtain photoluminescent carbon nanoparticlesdubbed as carbon‘quantum’dots.

Les procédés de photopolymérisation connaissent un développement important avec des applications considérables dans le milieu industriel en raison de ses avantages économiques et écologiques. Les réactions de photopolymérisation sont très représentées, elles reposent sur l’utilisation d’un composé ou d'un système photosensible sous irradiation, générant des espèces réactives capables d’amorcer la polymérisation et de réagir avec le monomère. Le principal objectif de ce travail de thèse consiste à développer des molécules efficaces comme photoamorceurs (PA) pour la photopolymérisation radicalaire (FRP) d’une part et la photopolymérisation cationique (CP) ou la photopolymérisation cationique sensibilisée par les radicaux (FRPCP) d’autre part. Nous nous sommes intéressés à des systèmes amorceurs hautes performances absorbant fortement dans le domaine du visible et permettant l’utilisation de lampes non nocives et à faible consommation d'énergie : les diodes électroluminescentes (LED). Ainsi, un procédé original portant sur la combinaison de la photopolymérisation radicalaire et la photopolymérisation cationique en une seule étape a été examiné. Cette approche a fait appel à la synthèse de réseaux interpénétrés de polymères (RIP) comportant les propriétés spécifiques de chaque polymère. Les efforts ont été consacrés au développement de nouveaux composés avec de nouvelles structures chimiques et d’excellentes propriétés d’absorption de lumière avec de coefficients d’extinctions molaires très élevés.Des systèmes construits sur l’utilisation de différentes structures comme photoamorceurs ont pu être mis au point dans le cadre de cette thèse. La possibilité d’utiliser des colorants présentant un caractère push-pull, ou des colorants étant caractérisés par une structure polyène ou une structure polyaromatique a pu être considérée. Egalement, des structures à base de xanthène sensibles dans le domaine proche visible ont pu être proposées. De plus, ce travail a permis d’étudier de nouveaux systèmes photoamorceurs à base de structures minérales telles que les polyoxométallates ou les pérovskites. Ainsi, la possibilité de proposer de nouveaux sels d’iodonium à base de coumarine a pu être démontrée. Des meilleures performances ont été atteintes en utilisant des systèmes photoamorceurs à deux composants (PA/Ph2I+) ou à trois composants (PA/Ph2I+/additif) dans des conditions d’irradiation douce. Afin d’étudier et caractériser ces photoamorceurs, la cinétique de la réaction de photopolymérisation a été suivie par spectroscopie infrarouge à transformée de Fourier (RT-FTIR). Les radicaux générés ont été détectés par résonance paramagnétique électronique (RPE). La photolyse laser éclair (LFP) a été utilisée comme technique complémentaire pour étudier l’efficacité et la réactivité de radicaux générés. / The photopolymerization reaction is used in an increasing number of industrial applications because of the remarkable performance of the process. The photopolymerization reactions require the presence of photosensitive compounds. These latter can absorb light and participate in the photoinitiation through the generation of reactive species. The main objective of this PHD was to develop efficient molecules as photoinitiators (PI) for the free radical photopolymerization (FRP), the cationic photopolymerization (CP) and the free radical promoted cationic photopolymerization (FRPCP). We were interested in new high performance photoinitiating systems (PISs) exhibiting excellent light absorption properties (especially in the visible wavelength range). The photopolymerization must be carried out under soft irradiation conditions (non harmful lamps, low energy consumption and low intensity sources: light-emitting diodes LED). Thus, a novel method involving concomitant radical/cationic photopolymerization in one step was examined. This approach involves the synthesis of interpenetrating polymer networks (IPNs) comprising the specific properties of each polymer. The efforts have been devoted to the development of new compounds with new chemical structures and excellent light absorption properties with high molar extinctions coefficients.Many PISs based on different photoinitiators structures have been developed in this work. The possibility to use dyes having a push-pull character, or dyes being characterized by a polyene or polyaromatic structures were considered. Also, originals xanthenes derivatives sensitive in the visible region have been proposed. In particular, this work has enabled the study of new PISs based on inorganic structures such as polyoxometalates and perovskites. Thus, the possibility to propose new iodonium salts based coumarin could be demonstrated. The best performance was achieved using two-components (PI/Ph2I+) or three-components (PI /Ph2I+/additive) photoinitiating systems under soft irradiation conditions. The kinetics of photopolymerization were evaluated using real time FTIR spectroscopy. The generated radicals were observed using the electron spin resonance (ESR) technique. The laser flash photolysis (LFP) was used as a complementary technique to study the efficiency and the reactivity of radicals generated.