The temperature and thermal stress distributions and variations of the high power LED module were studied in this work. The thermal-elastic-plastic 3D finite element models of MSC.marc software package are employed to simulate these performances for the high power LED module. Two high power white light LED module designs are investigated¡G one is the traditional phosphorescent silicone with blue LED module and the other is a phosphor glass lens with blue LED module. The distributions of temperature and thermal stress of in these two operating LED modules are compared and discussed. The effects of different packaging parameters¡Ge.g. bonding materials, substrate materials, lens materials on the temperature and thermal stress have also been studied in this work. The simulated results reveal that the serious thermal crack may occur for these two designs if the power of single die is over 10 watt. The simulated results also indicate that an attached fin cooler may improve these thermal crack disadvantaged significantly. The effect of fin design parameters on the peak temperature reduction has studied. A feasible fin design for the high power LED module has also been proposed.

Techniques to control dispersion in a medium have attracted much attention due to potential applications to devices such as ring laser gyroscopes, interferometric gravitational wave detectors, data buffers, phased array radars and quantum information processors. Of particular interest is an optical resonator containing a medium with an anomalous dispersion corresponding to fast-light, which behaves as a White Light Cavity (WLC). A WLC can be tailored to improve the sensitivity of sensing devices as well as to realize an optical data buffering system that overcomes the delay-bandwidth product of a conventional cavity. This dissertation describes techniques to tailor the dispersion for fast-light in intracavity media. We present first a demonstration of fast-light in a photorefractive crystal. When placed inside a cavity, such a medium could be used to enhance the bandwidth of a gravitational wave detector. We then describe how a superluminal laser can be realized by adding anomalously dispersive medium inside a ring laser. We identify theoretical conditions under which the sensitivity of the resonance frequency to a change in the cavity length is enhanced by as much as seven orders of magnitude. This paves the way for realizing a fast-light enhanced ring laser gyroscope, for example. This is followed by the development of a novel data buffering system which employs two WLC systems in series. In this system, a data pulse can be delayed an arbitrary amount of time, without significant distortion. The delay time is independent of the data bandwidth, and is limited only by the attenuation experienced by the data pulse as it bounces between two high-reflectivity mirrors. Such a device would represent a significant breakthrough in overcoming the delay-time bandwidth product limitation inherent in conventional data buffers. We then describe our experimental effort to create a fiber-based WLC by using stimulated Brillouin scattering (SBS). Experimental results, in agreement with our theoretical model presented here, show that the WLC effect is small under the conditions supported by current fiber optic technology. We conclude that future efforts to induce a large WLC effect would require fibers with high Brillouin coefficient and low transmission loss, as well as optical elements with very low insertion loss and high power damage thresholds.

ZnO material based hetero-junctions are a potential candidate for the design andrealization of intrinsic white light emitting devices (WLEDs) due to several advantages overthe nitride based material system. During the last few years the lack of a reliable andreproducible p-type doping in ZnO material with sufficiently high conductivity and carrierconcentration has initiated an alternative approach to grow n-ZnO nanorods (NRs) on other ptypeinorganic and organic substrates. This thesis deals with ZnO NRs-hetero-junctions basedintrinsic WLEDs grown on p-SiC, n-SiC and p-type polymers. The NRs were grown by thelow temperature aqueous chemical growth (ACG) and the high temperature vapor liquid solid(VLS) method. The structural, electrical and optical properties of these WLEDs wereinvestigated and analyzed by means of scanning electron microscope (SEM), current voltage(I-V), photoluminescence (PL), cathodoluminescence (CL), electroluminescence (EL) anddeep level transient spectroscopy (DLTS). Room temperature (RT) PL spectra of ZnOtypically exhibit one sharp UV peak and possibly one or two broad deep level emissions(DLE) due to deep level defects in the bandgap. For obtaining detailed information about thephysical origin, growth dependence of optically active defects and their spatial distribution,especially to study the re-absorption of the UV in hetero-junction WLEDs structure depthresolved CL spectroscopy, is performed. At room temperature the CL intensity of the DLEband is increased with the increase of the electron beam penetration depth due to the increaseof the defect concentration at the ZnO NRs/substrate interface. The intensity ratio of the DLEto the UV emission, which is very useful in exploring the origin of the deep level emissionand the distribution of the recombination centers, is monitored. It was found that the deepcenters are distributed exponentially along the ZnO NRs and that there are more deep defectsat the root of ZnO NRs compared to the upper part. The RT-EL spectra of WLEDs illustrateemission band covering the whole visible range from 420 nm and up to 800 nm. The whitelightcomponents are distinguished using a Gaussian function and the components were foundto be violet, blue, green, orange and red emission lines. The origin of these emission lines wasfurther identified. Color coordinates measurement of the WLEDs reveals that the emitted lighthas a white impression. The color rendering index (CRI) and the correlated color temperature(CCT) of the fabricated WLEDs were calculated to be 80-92 and 3300-4200 K, respectively.

Hologramas podem ser produzidos utilizando-se técnicas tradicionais de holografia ou podem ser gerados também por computador, conhecidos como hologramas gerados por computador (HGCs). A maioria destes hologramas opera usando luz monocromática. Por outro lado, os hologramas podem também operar com luz branca. Estes elementos de luz branca são usados em diversas aplicações, como segurança, para verificar a autenticidade dos cartões de crédito e outros documentos, porque seus processos de fabricação são difíceis e caros de serem reproduzidos. Entretanto, os hologramas de luz branca convencionais operam baseados na reflexão da luz, e apresentam alguns efeitos indesejáveis, como distorções cromáticas, como o efeito rainbow. Neste trabalho foi proposto um elemento óptico difrativo de luz branca gerado por computador. O elemento é calculado baseado na técnica de halftoning e na coerência espacial parcial de uma fonte de luz branca estendida. Os elementos da fase são produzidos através de técnicas de fabricação bem estabelecidas de circuitos integrados, e as simulações óticas são apresentadas. Não há necessidade de métodos iterativos. Os resultados das reconstruções ópticas e simuladas deste elemento de luz branca são muito semelhantes e produzem imagens nítidas, não sendo observadas distorções cromáticas. O elemento de luz branca ainda não foi descrito na literatura, e algumas de suas aplicações podem ser um correlator óptico ou arte holográfica. Este trabalho foi realizado no laboratório de óptica do departamento da engenharia elétrica do EESC, e financiado por CAPES (Coordenadoria de Aperfeiçoamento de Pessoal de Nível Superior). / Holograms can be produced using traditional holography techniques or may be also generated by computer, which are known as CGHs(Computer-generated holograms). Most of these holograms operate using monochromatic light. On the other hand, holograms can also operate with white light. These white light holograms are used in several applications, such as security, to verify the autencity of credit cards end other documents, because their fabrication processes are dificult to reproduce and are expensive. However, convencional white light holograms operate based on reflection of light, and present some undesirable effects, like chromatic distortions, such as rainbow effect. In this work it was proposed a computer-generated phase optical difractive element designed to operate under white light illumination. The element is calculated based on the halftoning technique and in the partial spatial coherence of a white light extended source. Phase elements are manufactured using well-established integrated circuits fabrication techniques and optical simulations are shown. No iterative methods are necessary. Simulated and optical reconstructions results are very similar and produce good clear images, and no chromatic distortions are observed. The white light element was not yet described on literature, and some of its applications may be an optical correlator or holographic art. This work was carried at the laboratory of optics of the department of electrical engineering of the EESC, and supported by CAPES (Coordenadoria de Aperfeiçoamento dePessoal de Nível Superior).

Orientador: Teresa Dib Zambon Atvars / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-24T04:00:22Z (GMT). No. of bitstreams: 1 Quites_FernandoJunior_D.pdf: 4476724 bytes, checksum: ad6fd1bd74a45cdc5e9333e1f66da8c0 (MD5) Previous issue date: 2013 / Resumo: Nesta Tese as propriedades foto e eletroluminescentes de diferentes polímeros conjugados foram abordadas: poli[(9,9-dioctilfluoreno-2,7-diil)-alt-co-(9,9-di-{5 f-pentanil}-fluoreno-2,7-diil)] (PFP) emissor na região do azul, poli[(9,9-dihexilfluoreno-2,7-diil)-alt-co-(bitiofeno)] (F6T2) emissor na região do verde e poli[2-metóxi-5(3 f,7 f-dimetiloctilóxi)1-,4-fenilenovinileno] (MDMO-PPV) emissor na região do vermelho. Primeiramente foram preparados materiais híbridos orgânico-inorgânico baseados em PFP e siliconas (polímeros de silício). Devido à presença de grupos vinílicos laterais na cadeia do PFP, estes foram ligados quimicamente às siliconas através da reação de hidrossililação produzindo dois tipos de siliconas: uma com menor grau (PDHS-PDVS-l-PFP-X) e outra com maior (PDHSS-PDVS-h-PFP-X) grau de reticulação. As propriedades fotofísicas destes materiais híbridos foram comparadas com o polímero PFP na forma de filme e em soluçõoes de THF e de diferentes polissiloxanos usados na reação de hidrossililação. Através de medidas de fotoluminescência no estado estacionário e medidas dinâmicas verificou-se que as cadeias de PFP estão desordenadas em solução e no filme fino e nas siliconas com menor grau de reticulação (PDHS-PDVS-l-PFP-X) independente da quantidade de PFP usada. Entretanto, nas siliconas híbridas com maior grau de reticulação (PDHSS-PDVS-h-PFP-X) uma fase cristalina, conhecida como fase a, foi formada. Além disso, nestes híbridos foram observados agregados emitindo em regiões de mais baixa energia quando a quantidade de PFP foi aumentada (PDHSS-PDVS-h-PFP-X, com X = 2 e 3). Portanto, a força dirigente para a formação da fase cristalina a pode ser pensada como uma combinação de interações p -p entre a cadeia principal planar do polímero e interações hidrofóbicas dos grupos laterais no ambiente mais confinado causado pelas cadeias das siliconas com maior grau de reticulação (PDHSS-PDVS-h-PFP-X). Após o estudo detalhado das propriedades fotofísicas do PFP tanto em solução como no estado sólido, blendas poliméricas baseadas neste polímero e no copolímero F6T2 foram preparadas. As investigações fotofísicas mostraram que há uma eficiente transferência de energia do doador PFP para o receptor F6T2 nestas blendas (PFP/F6T2). A transferência de energia se dá pelos processos não radiativo (mecanismo do tipo Förster) e radiativo. Foram também preparados diodos eletroluminescentes usando as blendas poliméricas de PFP/F6T2 como camada ativa (configuração do diodo ITO/PEDOT:PSS/blenda polimérica/Ca/Al) com a intenção de produzir dispositivos poliméricos emissores de luz branca (WPLEDs). Nestes dispositivos foi observada uma transferência de energia do PFP para o F6T2 e uma eficiente recombinação de cargas sendo favorecida nos domínios do copolímero F6T2, impossibilitando a preparação de WPLEDs empregando este dois componentes na mesma camada ativa. Como a preparação de WPLEDs foi comprometida usando blendas de PFP e F6T2, devido a eficiente recombinação de cargas nos domínios do F6T2, foi proposta uma metodologia empregando dois materiais poliméricos com propriedades de emissão de luz diferentes: um composto eletroluminescente, neste caso foi usado o PFP e outro composto fotoluminescentes (para isto foi escolhido o MDMO-PPV). Nesta metodologia foi construido um diodo EL baseado no polímero PFP (ITO/PEDOT/PSS:PFP/Ca/Al) que emitiu luz azul-esverdeada. Na face oposta deste dispositivo (onde há a saída de luz, substrato de quartzo/ITO) foi colocado um filme fino (depositado sobre um substrato de quartzo) do polímero MDMO-PPV. Este filme absorve na região da eletroemissão esverdeada do PFP, ou seja, a luz emitida pelo PFP e capaz de excitar as moléculas de MDMO-PPV, e ambos os componente emitem fazendo surgir uma emissão de luz branca. A cor branca foi confirmada pela coordenada de cromaticidade CIE (x = 0.35 e y = 0.31). / Abstract: In this work the photo and electroluminescent properties of the different conjugated polymers were investigated: poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(9,9-di(pent-4-en-1-yl)fluorene-2,7-diyl)]) (PFP) blue emitter, poly [(9,9-dihexilfluoreno-2 ,7-diyl)-alt-co-(bithiophene)] (F6T2) green emitter and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] ( MDMO -PPV ) red emitter. Firstly, we prepared organic-inorganic hybrid materials based on silicones and PFP polymer. The presence of vinyl moieties in the side chain of PFP react with Si-H groups of the silicone by the hydrosilylation producing two types of silicones: with lower (PDHS-PDVS-l-PFP-X) and higher (PDHSS-PDVS-PFP-h-X) crosslinking degree. The photophysical properties of these hybrid materials were compared with PFP polymer in film form and in the solutions of THF and of the different polysiloxanes used in the hydrosilylation reaction. Based on the steady-state and dynamic photoluminescence data, PFP chains are disordered in solutions, in the film and in the silicones with a lower degree of crosslinking (PDHS-PDVS-l-PFP-X) independent of the amount of PFP used. Nevertheless, in the hybrids with a higher degree of crosslinking (PDHSS-PDVS-PFP-h-X) the crystalline a-phase of the polyfluorene was formed. Aggregates emitting in longer wavelengths are only formed when other crystalline phases are present in PDHSS-PDVS-h-PFP-X (X = 2 and 3) silicones. The driving force for this formation is probably a combination of p - p interaction between the planar backbone and the hydrophobic interactions of the lateral groups in the poor solvent in a more confined environment such as brittle PDHSS-PDVS-h-PFP. After detailed study of the photophysical properties of PFP both in solution and in the solid state, polymer blends based on this polymer and in the F6T2 copolymer were prepared. The photophysical investigations showed that there is an efficient energy transfer from the donor (PFP) to the acceptor (F6T2) in these blends (PFP/F6T2). The energy transfer occurs by non-radiative process (Förster-type mechanism) and radiative. Electroluminescent diodes were also studied using polymer blends of PFP/F6T2 as active layer (device configuration: ITO/PEDOT:PSS/polymer blend/Ca/Al) with the intention of produce white polymer light-emitting diodes (WPLEDs). In these diodes was also observed an efficient energy transfer from the PFP to F6T2, and the charge recombination was favored in the dominions of the F6T2 copolymer. The higher transfer energy from donor to acceptor in these diodes compromised the blue light and the withe light using this polymer in the same active layer do not produced. Thus, white-emitting electroluminescent diode was obtained with a single layer of an electro-active greenish component (PFP) and an external photoluminescent (PL) red-emitting material (MDMO-PPV), in a diode configuration of ITO/PEDOT-PPS/PFP/Ca/Al//MDMO-PPV. A thin film of this PL component was deposited onto a glass plate and mounted on the opposite face of a glass/ITO substrate. The MDMO-PPV polymer electronic absorption matches the greenish electroemission of the PFP. The white color, based on the CIE color coordinates (x = 0.35 e y = 0.31), was obtained by the red emission of the external MDMO-PPV film and the blue-greenish EL emission from the formed PFP diode. White emission was produced by adjusting the absorbance of the layer thickness and the blue-greenish component until it reached the CIE white coordinates. / Doutorado / Quimica Inorganica / Doutor em Quimica

Conventional interferometry is widely used to measure spherical and flat surfaces with nanometer level precision but is plagued by back reflections. We describe a new method of isolating the measurement surface by controlling spectral properties of the source (Spectrally Controlled Interferometry - SCI). Using spectral modulation of the interferometer's source enables formation of localized fringes where the optical path difference is non-zero. As a consequence it becomes possible to form white-light like fringes in common path interferometers, such as the Fizeau. The proposed setup does not require mechanical phase shifting, resulting in simpler instruments and the ability to upgrade existing interferometers. Furthermore, it allows absolute measurement of distance, including radius of curvature of lenses in a single setup with possibility of improving the throughput and removing some modes of failure.

Thesis advisor: Baldassare Di Bartolo / Thesis advisor: Pradip Bakshi / The search for multicolored light produced by some IR laser-excited luminescent nano-powders has revealed, for laser power exceeding a threshold value, the emission of white light (WL) with black-body characteristics. I am directing my research to the study of the physical parameters that may influence the threshold power of the laser and the efficiency of the WL emission. A typical compound that I will investigate will consist of nano-powders of SrZrO3 doped with Yb. The parameters of relevance may include Yb concentration, pressure, temperature, size of nano-crystals, exciting power and wavelength of the laser, dynamical parameters such as decay and build-up patterns. The aim of my research will be both theoretical and experimental: theoretical for I will try to uncover the mechanism of the WL production and experimental for the possible application as efficient light sources of systems similar to the ones that I will investigate (oxide nano-powders doped with lanthanide or transition metal ions). The “new” light sources in the market (fluorescence lights sources, and LED lamps) beat the Edison bulbs in efficiency, but they do not produce the black-body emission of the Edison bulbs that is most pleasing to the eye. The search for efficient black-body type of sources is still on and we want to be a part of it. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

This work deals with the study of fluorescence lifetime and spectral changes of nanoparticles in cell biology. It describes the principle of fluorescence, fluorescence microscopy and laser confocal microscope Leica TCS SP8. The classic FLIM method, the Lambda Square mapping and the division of nanoparticles are introduced there. In the practical part, the created program for the evaluation of fluorescence lifetime and spectral changes is described. The program can show two-dimensional lambda maps, the fluorescence lifetime and spectral shift in the space area. In the final part of the thesis, an experiment with rhodamine nanoparticles is carried out and it is evaluated using the created program and then discussed.

Solar flares are common and strong demonstrations of solar activity. They are observable throughout the whole electromagnetic spectrum. If they show a broadband emission in the visible continuum, then we speak of white-light flares. The origin of white-light flares is not fully understood. We detected 24 white-light flares in SDO/HMI data and analyzed them using SDO/AIA wavelength bands at 1 700 ̊A and 304 ̊A and GONG Hα observations. According to our work, the emission in the 1 700 ̊A band is similar to the white-light emission but usually starts sooner. The positions of intensity enhancements in the 1 700 ̊A band are similar to the positions of the white-light flares and are connected by ribbons visible in the 304 ̊A band and in the Hα line. Then we studied the decay time of white-light flares and found that for most of the white-light flare points the typical decay time ranges in 2 - 3 min. 1

Artificial light at night (ALAN) is becoming a greater threat to nocturnal species. Aside from the overall increase in light output, replacing outdated monochromatic street lighting with light-emitting diode (LED) lights with a broad emission spectrum could raise this issue more. However, studies evaluating the effect of artificial lights on nocturnal species, such as moths, are scarce. This study examines any variations in moth attraction as well as any other sex-based behavioural differences (mating behaviour – wing fanning, trajectory-circular movement, overall movement time) between male and female moths in the presence of warm-white light. This study used warm-white light LED (2718 K) and Galleria mellonella moth, reared in the lab and completed the experiment under standardised conditions in an enclosed setting. I found the male moths (100%)  were significantly (p = 0.024) attracted to warm-white light LED compare to female moths (37%). While other behaviours such as wing fanning, circular movement, overall moving time, and favoured light illuminance for rest weren't significantly different (p > 0.05). In the future, it will be important to investigate the effects of warm-white light LED with different lower CCT (< 2718K) on moths, as well as the sex differences in their behaviour both in a controlled and an open environment. This will help authorities to decide on outdoor lighting systems in different countries and continents.