Intracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing of low vapor pressure compounds. We report here an ICLAS system design based on a quantum cascade laser (QCL) at THz (69.9 m) and IR wavelengths (9.38 and 8.1 m) with an open external cavity. The sensitivity of such a system is potentially very high due to extraordinarily long effective optical paths that can be achieved in an active cavity. Sensitivity estimation by numerical solution of the laser rate equations for the THz QCL ICLAS system is determined. Experimental development of the external cavity QCL is demonstrated for the two IR wavelengths, as supported by appearance of fine mode structure in the laser spectrum. The 8.1 m wavelength exhibits a dramatic change in the output spectrum caused by the weak intracavity absorption of acetone. Numerical solution of the laser rate equations yields a sensitivity estimation of acetone partial pressure of 165 mTorr corresponding to ~ 200 ppm. The system is also found sensitive to the humidity in the laboratory air with an absorption coefficient of just 3 x 10-7 cm -1 indicating a sensitivity of 111 ppm. Reported also is the design of a compact integrated data acquisition and control system. Potential applications include military and commercial sensing for threat compounds such as explosives, chemical gases, biological aerosols, drugs, banned or invasive organisms, bio-medical breath analysis, and terrestrial or planetary atmospheric science.

Tapered slot antennas (TSAs) have seen considerable application in the millimeter-wave portion of the spectrum. Desirable characteristics of TSAs include symmetric E- and H-plane antenna patterns, and broad non-resonant bandwidths. We investigate extension of TSA operation toward higher frequencies in the thermal infrared (IR), using a metal-oxide-metal diode as the detector. Several different infrared TSA design forms are fabricated using electronbeam lithography and specially developed thin-film processes. The angular antenna patterns of TSA-coupled diodes are measured at 10.6 micrometer wavelength in both E- and H-planes, and are compared to results of finite-element electromagnetic modeling using Ansoft HFSS. Parameter studies are carried out, correlating the geometric and material properties of several TSA design forms to numerical-model results and to measurements. A significant increase in antenna gain is noted for a dielectric-overcoat design. The traveling-wave behavior of the IR TSA structure is investigated using scattering near-field microscopy. The measured near-field data is compared to HFSS results. Suggestions for future research are included

No description available.

A reverse Monte-Carlo ray trace capable of performing a radiative analysis on arbitrary multiple overlapping structured computational fluid dynamics solution sets is developed. In order to make effective use of time, a method based on a set of simplifying assumptions but using the same calculation procedures is developed for comparison and study purposes. Three acceleration techniques are tried. One acceleration technique reduces the grid dimensions to reduce the number of volumes intersected. The second acceleration technique develops a version of the code for execution in a parallel processing environment. The third acceleration technique mixes an orthogonal, evenly spaced grid with the computational fluid dynamics grids to obtain fast ray traversal of low variance areas while retaining the higher resolution of the computational fluid dynamics grids in the high variance areas. Two experimental data sets are used for comparison and as test cases during these studies: an exhaust plume from an auxiliary power unit, and a Boeing 747 in flight. Timing for the baseline and accelerated analyses is provided as well as numerical comparisons for a selected subset. / Ph. D.

No description available.

No description available.

Wind power is one of the fastest growing production methods of electric energy. The expansion of wind power in Sweden are focused to northern counties. There are advantages as good wind conditions and large unexploited areas to build wind farms in the north, but there are also problems caused by the long winters. Due to the long periods of cold climate, ice and snow accumulation on blades are a safety risk, induces production losses and causes wear at wind turbine components. The commercial de-icing systems are not fulfilling the demands of being cost effective and are mainly focusing the heating to the leading edge. Therefore a new de-icing system based on infrared radiation has been investigated. This system is supposed to be placed at the wind turbine tower and de-ice one blade at a time. Experiments with this new de-icing system has been performed in small and full scale at a section of a real wind turbine blade. The experiments were carried out in facilities of Arctic Falls in Piteå. Different parameters as power demand of the heaters, distance between blade and heaters, wavelength of the radiation, influence by the surrounding temperature and total de-icing time were evaluated. Results showed that the largest impact of the efficiency and de-icing time were induced by the distance and width of the radiation spectrum for the heaters. Three types of filaments with different peaks of wavelengths were investigated and the most efficient de-icing was achieved when using a combination of heaters. Measurements of intensity together with de-icing experiments showed that the optimal distance from the blade was 1.5 m for heaters with standard reflectors. The main conclusion from the experiments with an infrared de-icing system is that it works. But not efficient enough to compete with the commercial systems of today even though it manage to de-ice the whole blade instead of just the leading edge. But this de-icing system has good potential if the heaters first of all are developed to radiate a more concentrated beam of radiation that is only focusing at the blades. The new method is estimated to be an lower investment due to that the techniques of infrared heaters are already well implemented in other areas. But more economic calculations has to be done to further motivate the work.

Criar um ambiente experimental capaz de medir a resposta neural da visão (térmica) - em serpentes - quando estimulada por radiação infravermelha. Tratou-se da criação de estímulos dinâmicos artificiais dos quais a temperatura e a velocidade de deslocamento foram controlados. A resposta da cobra, quanto a esses estímulos, foi captada diretamente do cérebro da mesma (teto óptico), que corresponde aos processos visuais e infravermelhos do sistema nervoso central da cascavel. Mostramos que com esses estímulos criados, foi possível obter dados experimentais capazes de viabilizar analises de sensibilidade do sistema sensorial infravermelho em relação a contraste em temperatura e velocidade de movimento de presas artificiais. / The present work describe a creation of an experimental environment capable of measuring the neural response of vision (thermal) -in snakes -when stimulated by infrared radiation. There will be a creation of artificial dynamic stimuli of which the temperature and displacement velocity can be controlled. The response of the snake, when presented to these stimuli, captured directly from the brain (tecto optic), which corresponds to visual and infrared process in the central nervous system of the rattlesnake. We showed that with these stimuli created, it is possible to obtain experimental data which will allow analysis of sensitivity of the infrared sensory system in relation to contrast in temperature and speed of movement of false prey.

Foi estudada a dissociação multifotônica do éter dietílico induzida por absorção de luz infravermelha, proveniente de um laser de CO2, tipo TEA.Na irradiação com a linha P(20) da banda 0001-0200 (1046 cm -1 ), os produtos observados por análise espectroscópica infravermelha e cromatografia em fase gasosa foram:H2,CO,CH4,C2H2,C2H4, C2H6, CH3CHO e C2H5OH.A eficiência de dissociação foi proporcional às pressões iniciais de éter a uma potência fixa e crescente em função da potência do laser a uma pressão fixa. A eficiência com relação ao comprimento de onda do laser seguiu aproximadamente o espectro de absorção I.V. do éter, sugerindo que a dissociação seja iniciada por um processo de absorção multifotônica ressonante. 0 estudo da variação do rendimento individual dos produtos em função da potência apresentou um comportamento crescente para todos os produtos, enquanto que a variação do rendimento individual dos mesmos em função da pressão inicial de éter para CO e CH4 foram crescentes e para C2H6, CH3CHO e C2H5OH foram decrescentes; o comportamento do C2H4 foi linear e quase constante, o que sugere que ele se forme por dissociação unimolecular do éter, enquanto que a formação de CO, CH4 e C2H6deve envolver processos colisionais. Na irradiação de misturas de éter com argônio, neônio, hidrogênio, hélio e N20, os rendimentos individuais absolutos cairam, possivelmente porque tais gases agem como desativadores de moléculas de éter excitadas pelo laser, por transferência de energia V-T. Adicionando-se ao éter um captador de radicais, no caso NO, foi verificado apenas um pequeno aumento no rendimento relativo de CH4 em detrimento do C2H6. Na irradiação o do sistema éter/oxigênio foi observada a quebra dielétrica do sistema, tratando-se este fenômeno de uma verdadeira combustão, uma vez que o processo todo é desencadeado com apenas um pulso do laser para pressões acima de 40,0 Torr de 02,sendo CO2o produto principal. Entretanto, abaixo do limiar de quebra dielétrica o rendimento individual dos produtos foi crescente com o aumento do número de pulsos e também em função do aumento da pressão de 02, exceto o etanol que neste último estudo decresceu. Neste caso, os produtos observados foram os mesmos que no éter puro, exceto pequena quantidade de CO2. Em síntese, o C2H4 e C2H5OH devem se formar da dissociação unimolecular do éter, ao passo que H2 , CO, CH4 , C2H2 , C2H6 e CH3CHO são obtidos, em sua maior parte, através de reações que envolvem processos colisionais, radicalares ou não. / The photodissociation of diethyl ether induced by infrared multiphoton absorption from focused radiation of a TEA CO2 laser was investigated. After irradiating with the P(20) line of the 0001-0200 band (1046 cm-1) the decomposition products were analyzed by IR spectroscopy and gas chromatography. Hydrogen, carbon monoxide, methane, ethylene, acetylene, ethane, acetaldehyde and ethanol were detected. The overall decomposition efficiency was proportional to the initial pressure for a fixed irradiation energy, and increases with pulse energy at constant sample pressure. The decomposition efficiency was also observed to be wavelength dependent and followed, roughly, the IR absorption spectrum profile suggesting a resonant multiphoton absorption initiated reaction. Individual product yields were found to increase by increasing pulse energies. The variation of the initial ether pressure showed increasing yields for CO and CH4, and decreasing yields for C2H6, CH3 CHO and C2H5OH. The C2H4 yield was almost constant with sample pressure, suggesting that it is formed through unimolecular decomposition, while the formation of CO, CH4 and C2H6 must involve collisional processes. The use of argon, helium, neon, hydrogen, and nitrous oxide as buffer gases decreases the absolute product yields, probably due to the deactivation of excited molecules via collisional V-T energy transfer. The use of a free radical scavenger, nitric oxide,indicated a small increase for CH4 yield and a decrease for C2H6. When irradiating ether/oxygen mixtures, a strong reaction initiated by dielectric breakdown was observed. This phenomenon occurs with one laser pulse when the oxygen pressure is above 40 Torr, and is practically a true combustion, resulting in the formation of CO2 as the major product and traces of CO. However, under the threshold for dielectric breakdown the products yields increase when increasing the number of pulses and 02 pressure. In this case the products are the same as in neat ether, except for small quantities of CO2.

Condensed matter systems exhibit a variety of dynamical phenomena at low energy scales, from gigahertz (GHz) to terahertz (THz) frequencies in particular, arising from complex interplay between charge, spin, and lattice. A large number of collective and elementary excitations in solids occur in this frequency range, which are further modified and enriched by scattering, interactions, and disorder. Recent advancements in spectroscopic methods for probing low-energy dynamics allow us to investigate novel aspects of charge and spin dynamics in solids. In this dissertation work, we used direct current (DC) conductivity, GHz, THz, and mid-infrared (MIR) techniques to provide significant new insights into interaction and disorder effects in low-dimensional systems. Specifically, we have studied temperature-dependent magnetoresistance (MR) and electron spin resonance (ESR) in single-wall carbon nanotubes (SWCNTs), intra-exciton scattering in InGaAs quantum wells, and high-field MIR-induced band gaps in graphene. Temperature-dependent resistance and MR were measured in an ensemble of SWCNTs from 0.3 to 350 K. The resistance temperature behavior followed a 3D variable range hopping (VRH) behavior from 0.3 to ~100 K. A positive MR was observed at temperatures above 25 K and could be fit with a spin-dependent VRH model; negative MR was seen at low temperatures. In the GHz regime, the ESR linewidth for SWCNTs was observed to narrow by as much as ~50% as the temperature was increased from 3 to 300 K, a phenomenon known as motional narrowing, suggesting that we are detecting the ESR of hopping spins. From the linewidth change versus temperature, we find the hopping frequency to be 285 GHz. For excitons in InGaAs quantum wells, we demonstrate the manipulation of intra-excitonic populations using intense, narrow-band THz pulses. The THz radiation temporarily quenches the 1s emission, which is then followed by an enhancement and subsequent decay of 2s emission. After the quenching, the 1s emission recovers and then eventually becomes enhanced, a demonstration of energy storage in intra-exciton states known as excitonic shelving. We show that the diffusive Coulomb scattering between the 2p and 2s states produces a symmetry breaking, leading to a THz-field-induced 1s-to-2s exciton population transfer.