Monitoring of environmental pollutants present at low concentrations requires creation of miniature, low-cost, and highly sensitive detectors that are capable to specifically identify target substances. In this thesis, a detection approach based on refractive index sensing with polymer micro-lasers is proposed and its application to the detection of heavy metal pollutants in water (mercury - Hg2+, cadmium - Cd2+ and lead - Pb2+) is studied. The resonance frequencies of the microcavity are highly sensitive to the refractive indices of the resonator surrounding: the resonances shift by a small amount when the surface refractive index changes, resulting from the interaction of the mode evanescent field with the surrounding medium. This permits label-free detection by coating the resonator with a suitable recognition species. The originality of this work lies in the utilization of active microcavities, or microlasers, created of the dye-doped polymers. Active microcavities offer an enhanced signal/noise ratio as compared to the passive ones and very narrow resonance peaks even at moderate quality factors (Q &#8805- 6000). The choice of polymers as an active medium is connected with a number of advantages they offer: as opposite to semiconductors, polymers can be easily functionalized, integrated in microfluidic circuits and are cheaper in processing. Moreover, the use of porous polymer matrices may allow accumulation of analyte ions inside the microcavity and thus enhance the sensitivity. Two possible applications of microlasers are investigated in the thesis: refractive index variation sensing with non-functionalized cavities and heavy metal ion detection with functionalized cavities. In the first case, the sensitivity values have been obtained, comparable with the reported in literature for planar passive microresonators. In the second case, the experimental proofs of specific detection of mercury ions in liquid are presented. The ways of sensitivity improvement are discussed and verified and a foundation is layed for the creation of integrated Lab-on-Chip microfluidic biochemical detector.

Darbe pristatomi eksperimentiniai bei teoriniai rezultatai, susiję su skaidriųjų terpių lūžio rodiklio pokyčio indukavimu. Parodoma, kad lydytą kvarcą veikiant Yb:KGV lazerine sistema generuojamais impulsais, jame galima sukurti modifikuoto lūžio rodiklio sritis. Šios sritys pasižymi dvejopu šviesos lūžimu, atsirandančiu dėl medžiagos tūryje besiformuojančių nanogardelių, o modifikuotų sričių vienalytiškumas priklauso nuo akumuliacinių efektų. Pakitusio lūžio rodiklio sritis taip pat galima formuoti ir ličio niobato kristale. Priklausomai nuo spinduliuotės parametrų, šiame kristale galima įrašyti stabilius modifikuoto lūžio rodiklio darinius, o taip pat ir nestabilias modifikacijas, atsirandančias dėl fotorefrakcinio reiškinio. Pastarąjį efektą galima panaudoti daugkartiniam informacijos įrašymui. Pademonstruoti efektyvūs fotoniniai elementai, tūrinės Brego gardelės, įrašytos tiek lydyto kvarco, tiek ličio niobato kristalo tūryje. Pateikiama metodika, skirta lazerio indukuoto lūžio rodiklio pokyčiui nustatyti matuojant Brego gardelių difrakcinius efektyvumus. Taip pat tyrinėjama kaip modifikuoti dariniai lemia superkontinuumo ir šviesos gijos formavimosi reiškinius lydytame kvarce. / The study on refractive index modification of transparent materials with ultrashort laser pulses is presented in this dissertation. Based on experimental data it was demonstrated, that using ultrashort pulses, generated with Yb:KGW laser system, it is possible to produce modified refractive index zones in the fused silica glass, that possess birefringence. This effect is caused by nanogratings that form in the bulk of the material. Homogeneity of the modified zones is determined by the accumulation effects, mainly the number of pulses that affect each area. Refractive index variations can be created also in crystalline material such as lithium niobate. Depending on the writing pulse parameters different types of modifications can be created: permanent modification that is caused by crystal amorphization and non-stable modifications that originate from the photorefractive properties of the crystal. Latter modifications can be used for three-dimensional, rewritable data recording. Highly efficient photonic elements, such as volume Bragg gratings, recorded in fused silica and lithium niobate crystal are demonstrated. The technique allowing the evaluation of refractive index change applying Bragg gratings is described. Also modification influence on nonlinear processes that appear in fused silica such as filament formation and supercontinuum generation is experimentally investigated.

The study on refractive index modification of transparent materials with ultrashort laser pulses is presented in this work. Based on experimental data it was demonstrated, that using ultrashort pulses, generated with Yb:KGW laser system, it is possible to produce modified refractive index zones in the fused silica glass, that possess birefringence. This effect is caused by nanogratings that form in the bulk of the material. Homogeneity of the modified zones is determined by the accumulation effects, mainly the number of pulses that affect each area. Refractive index variations can be created also in crystalline material such as lithium niobate. Depending on the writing pulse parameters different types of modifications can be created: permanent modification that is caused by crystal amorphization and non-stable modifications that originate from the photorefractive properties of the crystal. Latter modifications can be used for three-dimensional, rewritable data recording. Highly efficient photonic elements, such as volume Bragg gratings, recorded in fused silica and lithium niobate crystal are demonstrated. The technique, allowing the evaluation of refractive index change applying Bragg gratings, is described. Also modification influence on nonlinear processes that appear in fused silica such as filament formation and supercontinuum generation is experimentally investigated. / Darbe pristatomi eksperimentiniai bei teoriniai rezultatai, susiję su skaidriųjų terpių lūžio rodiklio pokyčio indukavimu. Parodoma, kad lydytą kvarcą veikiant Yb:KGV lazerine sistema generuojamais impulsais, jame galima sukurti modifikuoto lūžio rodiklio sritis. Šios sritys pasižymi dvejopu šviesos lūžimu, atsirandančiu dėl medžiagos tūryje besiformuojančių nanogardelių, o modifikuotų sričių vienalytiškumas priklauso nuo akumuliacinių efektų. Pakitusio lūžio rodiklio sritis taip pat galima formuoti ir ličio niobato kristale. Priklausomai nuo spinduliuotės parametrų, šiame kristale galima įrašyti stabilius modifikuoto lūžio rodiklio darinius, o taip pat ir nestabilias modifikacijas, atsirandančias dėl fotorefrakcinio reiškinio. Pastarąjį efektą galima panaudoti daugkartiniam informacijos įrašymui. Pademonstruoti efektyvūs fotoniniai elementai, tūrinės Brego gardelės, įrašytos tiek lydyto kvarco, tiek ličio niobato kristalo tūryje. Pateikiama metodika, skirta lazerio indukuoto lūžio rodiklio pokyčiui nustatyti matuojant Brego gardelių difrakcinius efektyvumus. Taip pat tyrinėjama kaip modifikuoti dariniai lemia superkontinuumo ir šviesos gijos formavimosi reiškinius lydytame kvarce.

Baigiamajame magistro darbe suprojektuotos ir pagamintos dviejų rūšių šviesos koncentratorinės sistemos: jungtinė parabolinė ir sistema su Frenelio lęšiu. Atlikta saulės elementų efektyvumo analizė, išnagrinėtos šviesą koncentruojančių sistemų rūšys bei aptarti jų optiniai parametrai. Frenelio lęšis ir koncentratorinių sistemų laikančiosios konstrukcijos pagamintos vakuuminio formavimo būdu, ieškant pigesnės gamybos technologijos. Baigiamajame darbe atlikti optinio pralaidumo ir lūžio rodiklio, matomos šviesos bangų ilgių ruože, tyrimai bei saulės elementų, esančių šviesos koncentratorinėse sistemose,voltamperinių ir voltvatinių charakteristikų tyrimai. Iš tyrimų rezultatų nustatyti šviesos koncentravimo laipsniai. Darbe diskutuojama apie pigių optinių sistemų galimus pritaikymus ir jų tobulinimo būdus. Išnagrinėjus teorinę ir praktinę dalis, pateiktos išvados ir pasiūlymai. Darbą sudaro 8 dalys: įvadas, saulės elementų efektyvumo ribos, saulės šviesos koncentratoriai ir jų panaudojimas fotoelektrinėse sistemose, eksperimentinių tyrimų metodika, prototipų gamyba, eksperimentiniai tyrimai, išvados, literatūros sąrašas. Darbo apimtis – 82 p. teksto be priedų, 95 pav., 13 lent., 22 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai. / Concentrated PV systems (compound parabolic and Fresnel CPV) have been designed and investigated. The efficiency of solar cells and the types of light concentrated systems have been analyzed and their optical parameters have been discussed. Fresnel lens and the CPV system holding structure have been fabricated by means of vacuum forming machine in this way making the technology of production less expensive. Optical transmittance and refractive index of Fresnel lens were measured in the range of visible light wavelengths. Current-voltage and voltage-power characteristics of solar cells built inside the CPV systems were investigated, based on results the degree of light concentration by Fresnel lens and compound parabolic CPV has been determined. Some discussions regarding possible applications of concentrated PV systems containing the Fresnel lens as well as possible ways of CPV design improvements are given in current work. After analysed theoretical and practical parts, conclusions and suggestions are proposed. Thesis structure: introduction, theoretical and experimental parts, results of experiments, conclusions and references. Thesis consist of: 82 p. text without appendixes, 95 pictures, 13 tables, 22 bibliographical entries. Appendixes included.

Salinity and turbidity are two important seawater properties for the physical oceanography. The study of physical oceanography requires a compact high-resolution in-situ salino-turbidi-meter. The main objective of this work is to propose, design and implement an optical solution to simultaneously measure the seawater salinity and turbidity. Our first study is carried out to design a high-resolution refractometer based on a laser beam deviation measurement by a Position Sensitive Device (PSD). The refractive index measurements obtained by the voltage value delivered by PSD have been evaluated to quantify the performances of the sensor. According to the obtained results, it is clear that this PSD-based refractometer is attractive for innovative applications in metrology. However, PSD lacks the capability to retrieve the power distribution information of laser beam, which is related to the turbidity measurements. On the contrary, Charge-Coupled Device (CCD) gives much more information of laser beam than PSD. In the second part of the thesis, a performance comparison between PSD and CCD combined with a centroid algorithm are discussed with special attention paid to the CCD-based refractometer. According to the operating principle of CCD-based system, five factors of CCD-based system: image window size, number of processed images, threshold, binning and saturation are evaluated to optimize the CCD-based refractometer. By applying the optimized parameters, the performance of CCD-based refractometer is better than PSD-based refractometer in measuring the refractive index. Furthermore, by applying different post-processing algorithms, CCD-based system possesses the capability of measuring the power distribution sensitive quantities. To show this advantage of CCD-based system, the attenuation measurement method is used to measure turbidity without modifying the refractometer configuration. The turbidity measurement and salinity measurements influence each other in a refractometer. To overcome these influences, a CCD combined with a new location algorithm is used to measure both the refractive index and the attenuation. Several simulations and experiments are carried out to evaluate this new method. According to the results, the way to improve the resolution is discussed as well. Comparing to the nephelometer specified by the NTU standard, our method has been proved as a valid method to measure turbidity. By studying the performances of CCD-based refracto-turbidi-meter, 3 new prototypes are proposed to improve the salinity and turbidity measurement performance at the end of this thesis.

Various carbon content hydrogenated amorphous silicon carbide (a-Si1&iexcl / xCx:H) and hydrogenated amorphous silicon (a-Si:H) thin films have been deposited on various substrates by using plasma enhanced chemical vapour deposition (PECVD) technique. Transmission spectra of these films have been determined within UV-Visible region and the obtained data were analysed to find related physical constants such as / refractive indices, thicknesses, etc. Fourier transform infrared (FT-IR) spectrometry technique has been used to determine transmission &amp / reflection type spectra of these films. Obtained data were analysed to determine bond structures of the films. E&reg / ects of relative concentration of ethylene (C2H4) gas on thin film bond structure and on optical constants have been questioned.

While prolonged nearwork is considered to be an environmental risk factor associated with myopia development, an underlying genetic susceptibility to nearwork-induced accommodative adaptation may be one possible mechanism for human myopia development. As the control of accommodation by the autonomic system may be one such genetically predetermined system, this research sought to investigate whether an anomaly of the autonomic control of accommodation may be responsible for myopia development and progression. The emphasis of this work was determining the effect of altering the sympathetic input to the ciliary muscle on accommodation responses such as tonic accommodation and nearwork-induced accommodative adaptation in myopes and non-myopes. The first study of the thesis was based on observations of Gilmartin and Winfield (1995) which suggested that a deficit in the sympathetic inputs to the ciliary muscle may be associated with a propensity for myopia development. The effect of ß-antagonism with timolol application on accommodation characteristics was studied in different refractive error groups. Our results support the previous findings that a deficit of sympathetic facility during nearwork was not a feature of late-onset myopia. However it was found that classifying myopes according to stability of their myopia and their ethnic background was important and this allowed differentiation between accommodation responses and characteristics of the ciliary muscle autonomic inputs, with the greatest difference observed between Caucasian stable myopes and Asian progressing myopes. Progressing myopes, particularly those with an Asian background, demonstrated enhanced susceptibility to nearwork-induced accommodative adaptation and this was suggested to result from a possible parasympathetic dominance and a relative sympathetic deficit to the ciliary muscle. In contrast, stable myopes, particularly those with an Asian background, demonstrated minimal accommodation changes following nearwork (counter-adaptation in some cases), and increased accommodative adaptation with ß-antagonism, suggesting sympathetic dominance as the possible autonomic accommodation control profile. As ethnic background was found to be an important factor, a similar study was also conducted in a group of Hong Kong Chinese children to investigate if enhanced susceptibility to nearwork-induced changes in accommodation may explain in part the high prevalence of myopia in Hong Kong. Despite some minor differences in methodology between the two studies, the Hong Kong stable myopic children demonstrated counter-adaptive changes and greater accommodative adaptation with timolol, findings that were consistent with those of the adult Asian stable myopes. Both Asian progressing myopic children and adults also showed greater accommodative adaptation than the stable myopes and similar response profiles following ß-adrenergic antagonism. Thus a combination of genetically predetermined accommodation profiles that confer high susceptibility and extreme environmental pressures is a likely explanation for the increase in myopia over the past decades in Asian countries. The hypothesis that a sympathetic deficit is linked to myopia was also investigated by comparing the effect of â-stimulation with salbutamol, a ß-agonist, on accommodation with that of ß-antagonism using timolol. It was hypothesized that salbutamol would have the opposite effect of timolol, and that it would have a greater effect on subjects who demonstrated greater accommodative adaptation effects, i.e. the progressing myopes, compared to those who showed minimal changes in accommodation following nearwork. Consistent with the hypothesis, the effect of sympathetic stimulation with salbutamol application was only evident in the progressing myopes whom we hypothesized may have a parasympathetic dominance and a relative sympathetic deficit type of autonomic imbalance while it did not further enhance the rapid accommodative regression profile demonstrated by the stable myopes. Characteristics of the convergence system and the interaction between accommodation and convergence were also investigated in the Hong Kong children. No significant differences in response AC/A ratios between the emmetropic, stable and progressing myopic children were found and it was concluded that elevated AC/A ratios were not associated with higher myopic progression rate in this sample of Hong Kong children. However, ß-adrenergic antagonism with timolol application produced a greater effect on accommodative convergence (AC) in stable myopic children who presumably have a more adequate, robust sympathetic input to the ciliary muscle, but had little effect on AC of progressing myopic children. This finding again points to the possibility that the autonomic control of the accommodation and convergence systems may be different between stable and progressing myopia. The primary contribution of this study to the understanding of myopia development is that differences in the autonomic control of the ciliary muscle may be responsible for producing anomalous accommodation responses. This could have significant impact on retinal image quality and thus results in myopia development. This knowledge may be incorporated into computer models of accommodation and myopia development and provides scope for further investigation of the therapeutic benefits of autonomic agents for myopia control.

The eye lens grows continuously throughout life and changes its shape as the eye changes focus from a distant to a near object (the process of accommodation). These changes are complex because they may affect not only the shape of the lens, but also its refractive index distribution. To date there has been no satisfactory technique for directly and non-invasively measuring these changes. In this study the refractive index distribution through the isolated lens was measured non-invasively using a novel MRI technique. The dependence of the refractive index value of lens tissue on its transverse relaxation rate (R2) was determined empirically from measurements on lens homogenate samples. Using a multi-spin-echo imaging sequence, data were acquired for constructing R2 maps of a central slice through the isolated lens. These R2 maps were transformed to refractive index maps using the empirically determined dependence of refractive index on R2. Using a standard algorithm for ray tracing through gradient index media, the propagation of light rays through the index map were simulated. The optical properties of the lens, such as focal length, were then measured. The technique was validated by also directly measuring the focal length of each lens using laser ray tracing. The subtle changes in refractive index distribution that are responsible for the dramatic change in the optical properties of the isolated lens with age, were observed for the first time. The decrease in surface power of the isolated lens with age accounted only partially for the decrease in total lens power with age, the remainder resulting from a reduction in the gradient of refractive index (GRIN) power. It is likely that this reduction in GFUN power is the mechanism by which the eye maintains emmetropia (good distant vision) with age despite the increasing curvature of its surfaces. The reduction in the GRIN power of the lens was found to be mainly due to a flattening of the refractive index profile in the central region of the lens, accompanied by steepening of the profile near the edge of the lens. In agreement with a previous MRI study of the isolated human eye lens, this study found a decrease in the refractive index of the nucleus with age. However the age related change in this study was not as large and not found to be statistically significant. The results demonstrate that existing simple models for the optics of the eye lens are inadequate to accurately describe its properties. Several more sophisticated models were considered in an attempt to describe better the age-dependent changes that occur in both the power of the lens and its longitudinal aberration. Mathematical modelling was also used to simulate the accommodative process and investigate possible changes in the index distribution of the lens that may occur with accommodation. A preliminary in vivo study was performed aimed at observing the change in the refractive index distribution of the eye lens with age and accommodation. These results demonstrated the feasibility of the technique for in vivo applications and showed that within experimental error there is little change in the central refractive index of the lens with age. However the resolution achievable with standard clinical imaging sequences and signal detection hardware was not optimal for in vivo refractive index mapping of changes in the human eye lens with accommodation. Finally therefore, methods for refining the technique for in vivo applications are discussed which may make it possible to directly and simultaneously measure both the shape and refractive index distribution of the lens with age and accommodation.

Myopia is a refractive defect of the eye in which collimated light produces images focused in front of the retina. Myopia can be artificially induced in animal models by form deprivation (form deprivation myopia, FDM) or by application of negative lenses (lens induced myopia, LIM). In this study myopia was induced using diffusers. The project had two main aims: 1. To determine if there is an interaction between the GABAergic system and dopaminergic system in the retina in terms of myopia? 2. To determine if there is an interaction between the GABAergic system and cholinergic system in the retina in terms of myopia? Firstly, an experiment focusing on the interaction between dopaminergic receptors antagonists and GABAC receptor antagonist was developed. Comparison of the different drug treated eye with the control was found and the effects of combination injections were compared to individual drug injections. Use of different blockers for various subtype of receptors simplified the understandings the underlying pharmacological interventions for GABAC receptor antagonist TPMPA. The D1 subtype of receptors was found to be involved in transmission of signals from GABAC receptors. Our results showed that D1 receptor antagonist SCH-23390 antagonizes the actions of TPMPA. In addition to this it was also found that possibly 5HT receptor may also play an important role in modulation of signaling from GABA receptor to dopaminergic receptors in the retina. These results were consistent with the drug combination effects for agonists. GABA A/C receptor agonist muscimol negativate the efficacy of D1 receptor agonist SKF-38393 but the activity of D2/4 receptor agonist quinpirole was not affected by muscimol. Although dopaminergic receptors are found to interact with GABAergic signaling, but an alternative interaction with anticholinergic (most widely studied antimyopic agents) could not be ruled out. This problem led to a follow-up experiment, in which GABA receptors intervention in anticholinergic agents was studied. The GABAergic receptor agonist muscimol when injected with anticholinergics (atropine and pirenzepine) showed a moderate interaction. As muscimol interacted with atropine to a lesser extent a more specific M1/5 receptor antagonist pirenzepine (earlier found to inhibit myopia) was used under these circumstances. The second aim to study the interaction between muscimol and pirenzepine showed more interaction with GABAA/C receptor agonist. There were data suggesting that there is a muscarinic and GABAergic interaction in retina, such that each modulation of each receptor had an effect on FDM. However, a drug combination treatment helped in understanding the underlying mechanism. Several previous studies have indicated that there exist a strong interaction between excitatory neurotransmitter acetylcholine and inhibitory transmitter GABA in retina. The results of this study indicate a similar finding. Thus results of this study may be summarized as: 1. D1 antagonists and not D2 antagonists blocks the antimyopic effects of GABAC antagonist TPMPA 2. GABA A/C agonist muscimol partially blocks the antimyopic activity of anticholinergics (e.g. atropine and pirenzepine).

Made available in DSpace on 2016-12-12T20:27:39Z (GMT). No. of bitstreams: 1 Renan Sebem.pdf: 14781648 bytes, checksum: 1c30002408823e0116831038c8c98e8c (MD5) Previous issue date: 2015-09-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work explores the potential and shows the implementation of the long period gratings as refractive index sensors. It is proposed a sensor design where the refractive index sensitivity is improved. The design includes the use of the sensor with simple and low cost interrogation. Several manufacturing parameters are investigated and the process is enhanced to meet the design specifications, and also to obtain repeatability in the process. New ideas were proposed to manufacture tilted gratings and to control the index modulation duty cycle in a practical way with inexpensive equipment. The inscription of the fiber sensor is made by CO2 laser, point to point, with a uniform index modulation. The gratings were interrogated by an optical spectrum analyzer and also by edge filter demodulation in the 1550 nm region through an electronic board, developed in this work with automatic normalization of the signal. Results show that the refractive index sensitivity is influenced by several design and manufacturing parameters of the fiber grating. Performed experiments show a considerable increase in the refractive index sensitivity of the grating. / Este trabalho explora o potencial e demonstra a implementação das redes de período longo em fibra como sensores de índice de refração. É proposto um projeto do sensor em que a sensibilidade ao índice de refração é aperfeiçoada. O projeto contempla a utilização do sensor com interrogação de maneira simples e de baixo custo. Diversos parâmetros de fabricação são investigados e o processo é aprimorado para atingir as especificações de projeto, e também a fim da obtenção de repetibilidade no processo. Novas ideias foram propostas para fabricação de redes inclinadas e para o controle do duty cycle da modulação de índice da rede de maneira prática com equipamentos de baixo custo. A fabricação do sensor em fibra é feita através de laser de CO2, ponto a ponto, e com modulação de índice uniforme. As redes foram interrogadas através de analisador de espectro óptico e também por demodulação de borda de filtro na região de 1550 nm através de uma placa eletrônica, desenvolvida neste trabalho com normalização automática do sinal. Resultados mostram que a sensibilidade ao índice de refração é influenciada por alguns parâmetros de projeto e fabricação da rede em fibra. Experimentos realizados mostraram um aumento considerável na sensibilidade da rede ao índice de refração.