During the past few decades, laser technology has had a strong impact on our society, providing important contributions to materials processing, data storage, communications, medicine, and defense applications. However, the progress in laser technology has also brought about the development of harmful portable high‐power lasers and tactical laser weapons. As a result, the hazard of being blinded by lasers (accidentally or from hostile use) has increased significantly. Hence, the need for protection against lasers has emerged. In order to protect optical sensors against harmful laser radiation, materials that absorb high intensity light, such as nonlinear absorbing chromophores, are employed. The concept of controlling the intensity of an optical light beam is usually referred to as optical power limiting and can be used efficiently in sensor protection devices.In this thesis, various nonlinear absorbing platinum(II) acetylides have been synthesized and characterized regarding their photophysical and optical limiting properties. Dendronized platinum(II) acetylides were prepared in order to evaluate the site isolation effect offered by the dendritic surrounding. The photophysical measurements reveal that the dendritic encapsulation enhances the phosphorescence, increases the luminescence lifetimes, and improves the optical limiting performance due to reduced quenching of the excited states.Triazole‐containing chromophores were synthesized using click chemistry to achieve functionalized platinum(II) acetylides. It was found that the position of the triazole unit affects the photophysical properties of these chromophores. The most promising results were obtained for the chromophore with the triazole located at the end of the conjugation where it may act as an electron donor, thus contributing to improved two‐photon absorption.A branched platinum(II) acetylide was also prepared in order to investigate the effect of multiple conjugated arms as well as multiple heavy atoms within the same molecule on the optical limiting performance. The star shaped chromophore reached the lowest clamping level of all compounds included in this thesis and constitutes a highly suitable chromophore for optical power limiting applications.The nonlinear absorbing chromophores were also incorporated into novel solid state materials based on PMMA. The actual device fabrication of doped organic glasses as optical limiters for sensor protection is presented, and their optical limiting performance is reported. The obtained organic glasses can reduce the transmission of high intensity light by 97 %. / QC 20100920

No description available.

Presbyopia is the progressive decrease in accommodative ability with age, and it implies a major loss of visual function. Presbyopia is the only condition of the eye which affects everyone who lives beyond 50 years of age. As part of a joint effort, the Ophthalmic Biophysics Center at the Bascom Palmer Eye Institute and the Vision Cooperative Research Centre at the University of New South Wales, developed two different ex-vivo accommodation simulators (EVAS) to examine the mechanisms of accommodation and presbyopia, and to test and validate new ophthalmic surgical procedures such as lens refilling. The purpose of this thesis is to mechanically and optically calibrate the second generation instrument (EVASII), and to compare it to the first generation design (EVASI). To validate the optical measurements of EVASII, an optical calibration has been performed, yielding a lens power measurement system with a mean accuracy of ±0.56D. To enhance the optical capabilities and tissue dissection options, the mechanics of mounting the tissue has been improved by using magnetic mounts, and the mechanical calibration of EVASII, yielded a force measurement system with a mean uncertainty of ±0.81g Also, a comparison of EVASII and EVASI has been performed, showing that the results of the two systems are significantly different; however, both systems successfully simulate accommodation. Thus, general trends concerning efficacy and optimization of surgical procedures as well as age related accommodative changes can be compared for each individual system.

High-intensity light — for instance that from a laser — can be destructive, not only to the human eye, but also to equipment such as imaging sensors and optical communication devices. Therefore, effective protection against such light is desirable. A protection device should ideally have high transmission to non-damaging light, and should also be fast-acting in order to effectively stop high-intensity light. In working towards a protection device, there is a need to conduct fundamental research in order to understand the processes involved. One of the photophysical processes of special interest in the field of optical power limiting (OPL) is reverse saturable absorption, where a compound in an excited state absorbs light more strongly than it does in its ground state. In this work, several novel organoplatinum compounds for OPL, rationally designed to have a strong reverse saturable absorption, have been synthesized. The compounds have been analyzed using linear and nonlinear absorption spectroscopy, luminescence spectroscopy, and quantum chemistry calculations to gain further knowledge regarding their photophysical properties. In addition to this fundamental research, the absorption capabilities of some of these compounds indicate that they can be used for OPL applications. Consequently, compounds from these studies have been incorporated into a sol–gel glass that could be used in optical systems. / <p>Finansiellt stöd från Kempestiftelsen.</p>

Interactions between light and a molecule can result in reversible or irreversible changes in properties of both the light and the molecule. Of the many known interactions, nonlinear absorption is a process in which an intense light signal, for instance from a laser, can be moderated. This can be manifested either in a marked lowering of the light’s intensity or in reductions in fluctuations of its intensity. Such an effect is often termed ‘optical power limiting’ (OPL). High power lasers can be very dangerous since their high intensity can damage or destroy eyes and optical sensors. However, there are currently no adequate protective measures against lasers that cover the entire visible region and there is an increasing demand for new or improved OPL materials. Some of the most promising optical power limiting materials are substances that combine nonlinear optical properties with high transparency in normal light, but after activation by a laser beam, their light transmittance falls extremely rapidly via so-called self-activating mechanisms. The platinum(II) acetylides comprise one class of compounds with such properties. In this study, various OPL Pt(II) acetylides were synthesized and their nonlinear optical properties were characterized. The emphasis of the work was on preparation of the compounds, but in order to design organoplatinum chromophores for OPL, attempts were also made to obtain insight into the mechanisms of nonlinear absorption. The work was divided into two main parts. In the first the goal was to find compounds that are good optical limiters in solution. The possibility of isolating the chromophore site by dendron shielding and the effects of incorporating a thiophene ring into the organic molecular system were also explored. In addition, a new route for synthesizing these compounds was developed. The second part was focused on incorporating the most interesting compounds into solid materials. The preparation and characterization of Pt(II) acetylides with molecular groups for covalent attachment to a silica matrix via the solution gel approach is described.

Light-emitting diodes (LED) illumination takes considerable applications in nowadays daily lives due to the improvement on efficiency of the LED modules. The connections between the reliability and the lifetime, power efficiency, optical spectrum, and structure design of the LED modules are the major research topics. In this study, high-power LED modules encapsulated with different lens shapes after a thermal-aging test were studied experimentally and numerically. The results showed that the LED modules encapsulated with a hemispherical-shaped plastic lens exhibited a better lifetime due to their better thermal dissipation than those with cylindrical- or elliptical-shaped plastic lenses. In the case of 80¢J aging test, the lifetime of hemispherical-shaped lens was 1.5 times better than the cylindrical- or elliptical-shaped lenses. Decay of radiation pattern and optical spectrum of high-power LED modules fabricated by different manufacturers after a thermal-aging test were investigated experimentally and numerically. The results showed that the radiation pattern of the LED modules at the two view angles of ¡Ó (15o~75o) decreased more than the other angles as aging time increased. Due to the degradation of lens material after thermal aging, the center wavelength of the LED spectrum shifted 5 nm. Furthermore, the radius curvature of plastic lens was observed 6-70 £gm contraction as aging times increased. Both experimental and simulated results clearly indicated that improving the lens structure and lens material is essential to extend the operating life of the high-power LED modules. High-power phosphor-converted white-light-emitting diodes (PC-LEDs) with selected concentration and thickness of Ce:YAG phosphor-doped silicones were investigated to study the thermal degradation effect of the Ce:YAG phosphor-silicone layer. The experimental results showed that the lumen loss, chromaticity (CIE shift), and spectrum intensity reduction increased as the concentration of Ce:YAG phosphor doped silicone increased. We showed that 94% lumen loss was attributed to 5.5 wt% Ce:YAG doping and only 6% of the lumen loss was due to a 1mm thickness of silicone degradation. From practical points of view, we found that a lower doping concentration of the Ce:YAG phosphor in thin silicone is a better choice in terms of having less thermal degradation for use in packaging of the high-power PC-LEDs modules and is essential to extend the operating lifetime of the phosphor-based white LED modules.

The polarization of light is one of the most remarkable phenomena in nature and has led to many discoveries in the optical-telecommunications sphere. The master's thesis describes the basic knowledge about polarized light, which includes the types of light polarization, the issue of Poincaré sphere, polarizing ellipse, etc. Emphasis is also placed on the measurement of optical power, where the analysis of various types of photodetectors and also polarimeters was performed. In the practical part of this work, the design of the workplace itself is described in the diagrams. Also, all devices in the workplace are analyzed and subsequently demonstrated measurement in several scenarios. The final chapter is a discussion with the measured results and graphical dependencies, comparison and analysis of results.

his paper discusses the characteristics of laser radiation. Introduces the theory and in quite a description of the laser beam. To this end, experiments were compiled to measure the geometric and performance parameters, polarization and coherence. Emphasis is placed on the interdependence of the various parameters of laser radiation

Ce mémoire de thèse est consacré à la mise en place d'un système opto-électronique générique basé sur une liaison toute optique bidirectionnelle de 10km. L'architecture étudiée et développée est dédiée à l'extension d'un observatoire câblé de fond de mer afin d'atteindre de nouvelles zones d'exploration. Les travaux de recherche rapportés dans ce manuscrit présentent la réalisation d'un démonstrateur, qui permet la récupération de données, issues d'un instrument connecté à un module opto-alimenté, via une seule fibre optique où transitent simultanément deux voies de données en bande C et la puissance optique d'alimentation (à 1480nm) égale à 33dBm permettant de récupérer 180mW électrique sur le module opto-alimenté.Le contexte de cette thèse de doctorat est présenté au travers d'un état de l'art sur les moyens utilisés pour l'observation des océans et sur les systèmes électroniques à faible consommation. Après un rappel des caractéristiques essentielles de l'architecture de la liaison optique préalablement établie, nous nous concentrons sur la structure opto-électronique qui a pour but d’assurer la communication entre l’observatoire et l’instrument déporté de l’extension. La définition du cahier des charges a abouti au choix du capteur (hydrophone), du débit des données (5Mbit/s) et du protocole de communication (SPI 3-fils) utilisé entre les deux modules opto-électroniques, chacun à une extrémité de la fibre optique. L'effort a été porté sur la conception d'un module opto-alimenté faible consommation (66mW) où s'intègre l'instrument. Tout au long de ce document, les choix technologiques retenus lors de la conception des deux modules opto-électroniques sont argumentés. Le banc d'essai du démonstrateur a permis de valider la conception de cette extension et d'évaluer la qualité de la transmission des données (BER inférieur à 10-6). Le fonctionnement d'un premier prototype destiné à être marinisé a été présenté au travers de la détection et de la transmission de signaux acoustiques générés en bassin d'essai. De manière à rendre le système encore plus générique, une solution alternative à base d'un FPGA, permettant l'utilisation d'une interface SPI 4-fils sans modifier la liaison optique a été présentée et validée. / This PhD thesis is devoted to the design of an opto-electrical and generic system which uses a 10km long all-optical and bidirectional link. The studied and developed system is dedicated to extend a current cabled seafloor observatory, in order to reach new exploration areas. The research work described in this thesis presents the development and the realization of a demonstrator. This later collects data from an instrument connected to its optically powered unit. The optical power supply (33dBm at 1480nm), which provides up to 180mW electrical for the optically powered unit, and the optical data in C band, are transmitted simultaneously through the same single optical fiber.The thesis context is first presented through an overview of ocean observation systems and low consumption electronic devices. After a brief review on the main characteristics of the optical architecture, we focused on the opto-electrical structure which permits the communication between the observatory and the remote instrument. The desired requirements have led us to the choice of the sensor (hydrophone), the data bit rate (5Mbit/s) and the communication protocol (SPI 3-Wire) used between both opto-electrical units, each one located at the both ends of the optical link. A special attention was devoted to the conception of the optically powered which must be low power consumption (66mW). All along this document, technical choices involved in the realization of both opto-electrical units are presented. We could evaluate the performance of the data transmission (BER less than 10-6) by using a demonstrator's test bench. Then, a first prototype designed for the ocean environment was presented through experimental measurements. Those tests were conducted in a test pool and have consisted in the detection of acoustic signals. In order to increase the range of compatible instruments, an alternative solution based on a FPGA was described and approved. This new design allows the SPI 4-Wire to be employed without any change of the current optical architecture.

Realization of spectral responsivity scale was studied in three stages. Firstly, absolute optical power measurements using Electrical Substitution Cryogenic Radiometer (ESCR) was studied. The absolute measurements were done at discrete laser wavelengths of tunable Ar+ (488 nm and 514.5 nm), Nd:YAG (532 nm) and fixed He-Ne (632.8 nm) laser sources. To increase measurement accuracy the method used for the stabilization of laser beams, transmittance measurements of optical windows, and minimization of scattered beams were discussed. Secondly, realization of absolute responsivity scale between 350- 850 nm ranges was studied. The scale based on reflection type trap detectors consisting of three silicon photodiodes. Various measurement systems were established in order to make optical characterization of trap detectors like non-linearity, surface non-homogeneity, polarization dependency, reflectance, and internal quantum efficiency. The absolute responsivity was linked to the absolute optical power by measuring the current response of trap detectors to the absolute power measured by ESCR system at laser wavelengths. Using models for the trap detector&rsquo / s, reflectance and internal quantum efficiency the scale between 350- 850 nm ranges was realized with an uncertainty of 0.05 %. Finally, the spectral responsivity scale in ultraviolet (UV) and near-infrared (NIR) regions was realized using Electrically Calibrated Pyroelectric Radiometer (ECPR). Optically characterizing the spatial non-uniformity of pyroelectric detector and its surface reflectance, the spectral responsivity scale was established with uncertainties &plusmn / 0.5-1.0 % between 250 nm and 350 nm and &plusmn / 0.5-1.5 % between 850 and 2500 nm.