published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

In the past several decades the technology for the creation and use of ultrashort pulses has progressed tremendously. Now, it is possible to generate laser pulses as short as a few femtoseconds in duration, and such pulses have been used for a wide range of applications. In addition, the means of measuring these pulses has progressed so rapidly. However, despite recent great advances in ultrashort-pulse measurement techniques, much remains to be done. In particular, pulse-measurement devices have relatively small wavelength-tuning ranges, and the phase-match is problematic for the pulses with a wide bandwidth such as supercontinuum. In this thesis, I will demonstrate a new pulse measurement technique which can phase-match ultra-broad bandwidth of super-continuum using transient grating frequency-resolved-optical-gating (TG FROG). Also, I will demonstrate a simplified device which can measure the UV ultra-short pulse using transient grating process, one of the third-order nonlinearity and can cover from UV to IR with the same arrangement.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

A new pulse-retrieval software for Frequency-Resolved Optical Gating (FROG) technique has been developed. The new software extends the capacity of the original FROG algorithm in two major categories. First is a new method to determine the uncertainty of the retrieved pulse field in FROG technique. I proposed a simple, robust, and general technique?tstrap method?ch places error bars on the intensity and phase of the retrieved pulse field. The bootstrap method was also extended to automatically detect ambiguities in the FROG pulse retrieval. The second improvement deals with the spatiotemporal effect of the input laser beam on the measured GRENOUILLE trace. I developed a new algorithm to retrieve the pulse information, which includes both pulse temporal field and the spatiotemporal parameters, from the spatiotemporal distorted GRENOUILLE trace. It is now possible to have a more complete view of an ultrashort pulse. I also proposed a simple method to remove the spatial profile influence of the input laser beam on the GRENOUILLE trace. The new method extends the capacity of GRENOUILLE technique to measure the beams with irregular spatial profiles.

In this thesis a powerful and practical method for characterizing ultrashort pulses in space and time is described (called SEA TADPOLE). First we focus on measuring pulses that are spatially uniform but very complicated in time or frequency. We demonstrate and verify that SEA TADPOLE can measure temporal features as small as 30 femtoseconds over durations as long as 14 picoseconds. The spectral resolution of this device is carefully studied and we demonstrate that for certain pulses, we achieve spectral super resolution. We also develop and test an algorithm for measuring polarization shaped pulses with SEA TADPOLE. Our simple interferometer can even be used to measure the spatiotemporal electric field of ultrashort pulses at a focus. This is because SEA TADPOLE samples the field with an optical fiber which has a small core size. Therefore this fiber can be used to spatially sample the beam, so that the temporal electric field can be measured at every position to obtain E(x, y, z, t). The single mode fiber can be replaced with an NSOM (Near Field Scanning Optical Microscopy) fiber so that spatial resolution as low as 500nm (and possibly lower) can be achieved. Using this device we make the first direct measurements of the compete field of focusing ultrashort pulses. These measurement can be viewed as "snap shots" in flight of the focusing pulse. Also, for the first time, we have observed some of the interesting distortions that have been predicted for focusing ultrashort pulses such as the "forerunner" pulse, radially varying group delay dispersion, and the Bessel-like X-shaped pulse. We have also made the first direct measurements of the electric field of Bessel X-pulses and their propagation invariance is demonstrated. We also use SEA TADPOLE to study the "boundary wave pulses" which are due to diffraction.

Made available in DSpace on 2015-01-26T13:21:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-28Bitstream added on 2015-01-26T13:30:40Z : No. of bitstreams: 1 000793002.pdf: 367626 bytes, checksum: 55a07e4af17ba3387e0dace8d01c9282 (MD5) / O objetivo do presente estudo foi avaliar o efeito da dexmedetomidina sob a variação da pressão de pulso (VPP) induzida pela hemorragia seguida por reposição volêmica (RV) em cães anestesiados com isoflurano. Em um estudo prospectivo, aleatorizado e cruzado, 8 cães adultos (19,5 a 29,2 kg) foram anestesiados com 1,3 de concentração alveolar mínima de isoflurano isolado isoflurano associado a infusão contínua de dexmedetomidina (2 μg/kg/h) com intervalo de 2 semanas entre os tratamentos. Administrou-se atropina (0,03 mg/kg pela via intramuscular, IM e 0,01 mg/kg pela via intravenosa, IV) 30 minutos antes da hemorragia no tratamento dexmedetomidina. Em ambos os tratamentos produziu-se bloqueio neuromuscular com atracúrio (bolus de 0,3 mg/kg, seguido por 0,3 mg/kg/hora) para realização de ventilação com volume controlado (volume corrente: 12 mL/kg, relação inspiração/expiração: 1:1,3, frequência respiratória de 16-20 mov/min) com pressão positiva no final da expiração de 7 cmH2O. Após a mensuração dos parâmetros no momento basal, iniciou-se a retirada progressiva de sangue na proporção de 10, 20 e 30% do volume total estimado (HV10, HV20, HV30, respectivamente), e na sequência realizou-se a reposição volêmica com sangue autólogo na mesma proporção (RV10, RV20 e RV30, respectivamente). Quatro dos 8 cães anestesiados com isoflurano apresentaram hipotensão [pressão arterial média (PAM) < 60 mmHg]. Com base nas alterações da PAM após a hemorragia nos cães anestesiados com isoflurano, os cães foram divididos em dois grupos: hipotenso (GH) e normotenso (GN). Durante a anestesia com isoflurano (GH e GN) o índice sistólico (IS) e o índice cardíaco (IC) reduziram-se significativamente (P < 0,05) em relação aos valores basais, enquanto após a reposição volêmica estas variáveis retornaram aos valores basais ou apresentaram aumento significativo. A VPP (%) [média (valores máximo e mínimo)] ... / This study aimed to evaluate the effects of dexmedetomidine on pulse pressure variation (PPV) changes induced by hemorrhage followed by volume replacement (VR) during isoflurane anesthesia. In a prospective, randomized crossover study, 8 adult dogs (19.5 to 29.2 kg) were anesthetized with 1.3 times the minimum alveolar concentration of isoflurane alone or isoflurane/dexmedetomidine (2 μg/kg/h) (2-week washout intervals). Atropine (0.03 mg/kg IM and 0.01 mg/kg IV) was administered 30 minutes prior to hemorrhage in the dexmedetomidine treatment. In both treatments neuromuscular blockade was produced by atracurium (0.3 mg/kg bolus, followed by 0.3 mg/kg/hour) for performing volume controlled ventilation (tidal volume: 12 mL/kg, inspiration to expriation ratio: 1:1.3 and respiratory rate: 16-20 breaths/min) with a positive end-expiratory pressure of 7 cm H2O. After recording baseline data, progressive withdrawal of 10, 20, and 30% of the estimated blood volume (HV10, HV20, and HV30, respectively) was followed by VR with autologous blood in the same proportion (RV10, RV20, and RV30, respectively). In 4/8 isoflurane-anesthetized dogs hemorrhage induced hypotension [mean arterial pressure (MAP) < 60 mmHg]. Based on MAP changes after hemorrhage during isoflurane anesthesia, dogs were divided in hypotensive (HG) and normotensive groups (NG). During isoflurane anesthesia (HG and NG), stroke index and cardiac index were significantly (P < 0.05) decreased from baseline after hemorrhage, while VR normalized or significantly increased these variables. The PPV (%) was increased by hemorrhage [from 7 (9, 5) (baseline) to 20 (27, 12) and 27 (40, 17) at HV20 and HV30, respectively] [mean (upper, lower ranges)] only in isoflurane-anesthetized dogs that became hypotensive; PPV returned to baseline after VR. Dexmedetomidine caused sustained increases in systemic vascular resistance (HG and NG), and prevented the ...

Orientador: Francisco José Teixeira Neto / Banca: Denise Tabacchine Fantoni / Banca: Carlos Alan Candido Dias Junior / Resumo: O objetivo do presente estudo foi avaliar o efeito da dexmedetomidina sob a variação da pressão de pulso (VPP) induzida pela hemorragia seguida por reposição volêmica (RV) em cães anestesiados com isoflurano. Em um estudo prospectivo, aleatorizado e cruzado, 8 cães adultos (19,5 a 29,2 kg) foram anestesiados com 1,3 de concentração alveolar mínima de isoflurano isolado isoflurano associado a infusão contínua de dexmedetomidina (2 μg/kg/h) com intervalo de 2 semanas entre os tratamentos. Administrou-se atropina (0,03 mg/kg pela via intramuscular, IM e 0,01 mg/kg pela via intravenosa, IV) 30 minutos antes da hemorragia no tratamento dexmedetomidina. Em ambos os tratamentos produziu-se bloqueio neuromuscular com atracúrio (bolus de 0,3 mg/kg, seguido por 0,3 mg/kg/hora) para realização de ventilação com volume controlado (volume corrente: 12 mL/kg, relação inspiração/expiração: 1:1,3, frequência respiratória de 16-20 mov/min) com pressão positiva no final da expiração de 7 cmH2O. Após a mensuração dos parâmetros no momento basal, iniciou-se a retirada progressiva de sangue na proporção de 10, 20 e 30% do volume total estimado (HV10, HV20, HV30, respectivamente), e na sequência realizou-se a reposição volêmica com sangue autólogo na mesma proporção (RV10, RV20 e RV30, respectivamente). Quatro dos 8 cães anestesiados com isoflurano apresentaram hipotensão [pressão arterial média (PAM) < 60 mmHg]. Com base nas alterações da PAM após a hemorragia nos cães anestesiados com isoflurano, os cães foram divididos em dois grupos: hipotenso (GH) e normotenso (GN). Durante a anestesia com isoflurano (GH e GN) o índice sistólico (IS) e o índice cardíaco (IC) reduziram-se significativamente (P < 0,05) em relação aos valores basais, enquanto após a reposição volêmica estas variáveis retornaram aos valores basais ou apresentaram aumento significativo. A VPP (%) [média (valores máximo e mínimo)] ... / Abstract: This study aimed to evaluate the effects of dexmedetomidine on pulse pressure variation (PPV) changes induced by hemorrhage followed by volume replacement (VR) during isoflurane anesthesia. In a prospective, randomized crossover study, 8 adult dogs (19.5 to 29.2 kg) were anesthetized with 1.3 times the minimum alveolar concentration of isoflurane alone or isoflurane/dexmedetomidine (2 μg/kg/h) (2-week washout intervals). Atropine (0.03 mg/kg IM and 0.01 mg/kg IV) was administered 30 minutes prior to hemorrhage in the dexmedetomidine treatment. In both treatments neuromuscular blockade was produced by atracurium (0.3 mg/kg bolus, followed by 0.3 mg/kg/hour) for performing volume controlled ventilation (tidal volume: 12 mL/kg, inspiration to expriation ratio: 1:1.3 and respiratory rate: 16-20 breaths/min) with a positive end-expiratory pressure of 7 cm H2O. After recording baseline data, progressive withdrawal of 10, 20, and 30% of the estimated blood volume (HV10, HV20, and HV30, respectively) was followed by VR with autologous blood in the same proportion (RV10, RV20, and RV30, respectively). In 4/8 isoflurane-anesthetized dogs hemorrhage induced hypotension [mean arterial pressure (MAP) < 60 mmHg]. Based on MAP changes after hemorrhage during isoflurane anesthesia, dogs were divided in hypotensive (HG) and normotensive groups (NG). During isoflurane anesthesia (HG and NG), stroke index and cardiac index were significantly (P < 0.05) decreased from baseline after hemorrhage, while VR normalized or significantly increased these variables. The PPV (%) was increased by hemorrhage [from 7 (9, 5) (baseline) to 20 (27, 12) and 27 (40, 17) at HV20 and HV30, respectively] [mean (upper, lower ranges)] only in isoflurane-anesthetized dogs that became hypotensive; PPV returned to baseline after VR. Dexmedetomidine caused sustained increases in systemic vascular resistance (HG and NG), and prevented the ... / Mestre

We demonstrate four experimentally simple methods for measuring very complex ultrashort light pulses. Although each method is comprised of only a few optical elements, they permit the measurement of extremely complex pulses with time-bandwidth products greater than 65,000. First, we demonstrate an extremely simple frequency-resolved-optical gating (GRENOUILLE) device for measuring the intensity and phase of pulses up to ~20ps in length. In order to achieve the required high spectral resolution and large temporal range, it uses a few-cm-thick second harmonic-generation crystal in the shape of a pentagon. This has the additional advantage of reducing the device's total number of components to three. Secondly, we introduce a variation of spectral interferometry (SI) using a virtually imaged phased array and grating spectrometer for measuring long complex ultrashort pulses up to 80 ps in length. Next, we introduce a SI technique for measuring the complete intensity and phase of relatively long and very complex ultrashort pulses. It involves making multiple measurements using SI (in its SEA TADPOLE variation) at numerous delays, measuring many temporal pulselets within the pulse, and concatenating the resulting pulselets. Its spectral resolution is the inverse delay range--many times higher than that of the spectrometer used. The waveforms were measured with ~ fs temporal resolution over a temporal range of ~ns and had time-bandwidth products exceeding 65,000, which to our knowledge is the largest time-bandwidth product ever measured with ~fs temporal resolution. Finally, we demonstrate a single-shot measurement technique that temporally interleaves hundreds of measurements with ~fs temporal resolution. It is another variation of SI for measuring the complete intensity and phase of relatively long and complex ultrashort pulses in a single shot. It uses a grating to introduce a transverse time delay into a reference pulse which gates the unknown pulse by interfering it at the image plane of an imaging spectrometer. It provided ~125 fs temporal resolution and a temporal range of 70 ps using a low-resolution spectrometer.

Pagrindinis darbo tikslas – sukurti plačiajuostį rezistorinį jutiklį, skirtą didelės galios mikrobangų impulsams matuoti, kurio jautrusis elementas pagamintas iš n-tipo Si yra įmontuotas H tipo bangolaidyje. Rezistorinis jutiklis turėtų pasižymėti plokščia jautrio dažnine charakteristika, jo varža neviršyti 1 k, o stovinčios bangos koeficientas būti mažesnis nei 1,5. Disertacijoje yra pateikiami teoriniai elektrinio lauko pasiskirstymo bangolaidinėje sekcijoje su rezistorinio jutiklio jautriuoju elementu viduje modeliavimo baigtinių skirtumų laiko skalėje metodu rezultatai, kai jautrusis elementas yra talpinamas standartiniuose H tipo bangolaidžiuose WRD250 ir WRD840. Modeliavimo metu buvo ieškoma tokių jautriojo elemento matmenų ir savitosios varžos, kad rezistorinis jutiklis tenkintų aukščiau paminėtus reikalavimus. Disertacijoje taip pat aprašomi trijų skirtingų rezistorinių jutiklių, kurių optimalūs matmenys buvo surasti iš modeliavimo rezultatų, eksperimentiniai tyrimai. Buvo nustatytos šių jutiklių jautrio dažninės charakteristikos, jutiklių atsako signalo priklausomybė nuo mikrobangų galios ir stovinčios bangos koeficientas. Sujungus sukurtąjį jutiklį su plačiajuoste ruporine antena buvo atlikti mikrobangų galios tankio (elektrinio lauko stiprio) matavimai atviroje erdvėje. Pateikti disertacijoje internetinių maršrutizatorių ir šviesolaidinių konverterių elektromagnetinio atsparumo tyrimai, kuriuose rezistoriniai jutikliai naudojami elektrinio lauko stipriui... [toliau žr. visą tekstą] / The main goal of the thesis was the development of a resistive sensor, a sensing element of which made from n-type Si is mounted in a double ridge waveguide. Developed sensor was devoted for the measurement of high power microwave pulses. The sensor should meet the following requirements: its resistance should be lower than 1 k, a voltage standing wave ratio has been set < 1.5, and the frequency response of the sensor should be as flat as possible. In the thesis the results of theoretical calculation of electromagnetic fields inside waveguide segment with the sensing element of the resistive sensor mounted in the standard double ridged waveguides WRD250 and WRD840 are presented. Calculations have been performed using finite-difference time-domain method. The dimensions and specific resistance of the sensing element from the modeling results were chosen for the sensor that meets the requirements mentioned above. Corresponding sensors have been manufactured and their characteristics have been investigated experimentally. The sensitivity dependence on frequency, output signal dependence on microwave pulse power and voltage standing wave ratio were determined. Connecting the sensor to a wide band horn antenna the microwave pulse power density (electric field strength) in free space was measured. Resistive sensors were used for electric field strength measurement in the immunity against microwave radiation tests on internet routers and media converters demonstrating possible... [to full text]

The main goal of the thesis was the development of a resistive sensor, a sensing element of which made from n-type Si is mounted in a double ridge waveguide. Developed sensor was devoted for the measurement of high power microwave pulses. The sensor should meet the following requirements: its resistance should be lower than 1 k, a voltage standing wave ratio has been set < 1.5, and the frequency response of the sensor should be as flat as possible. In the thesis the results of theoretical calculation of electromagnetic fields inside waveguide segment with the sensing element of the resistive sensor mounted in the standard double ridged waveguides WRD250 and WRD840 are presented. Calculations have been performed using finite-difference time-domain method. The dimensions and specific resistance of the sensing element from the modeling results were chosen for the sensor that meets the requirements mentioned above. Corresponding sensors have been manufactured and their characteristics have been investigated experimentally. The sensitivity dependence on frequency, output signal dependence on microwave pulse power and voltage standing wave ratio were determined. Connecting the sensor to a wide band horn antenna the microwave pulse power density (electric field strength) in free space was measured. Resistive sensors were used for electric field strength measurement in the immunity against microwave radiation tests on internet routers and media converters demonstrating possible... [to full text] / Pagrindinis darbo tikslas – sukurti plačiajuostį rezistorinį jutiklį, skirtą didelės galios mikrobangų impulsams matuoti, kurio jautrusis elementas pagamintas iš n-tipo Si yra įmontuotas H tipo bangolaidyje. Rezistorinis jutiklis turėtų pasižymėti plokščia jautrio dažnine charakteristika, jo varža neviršyti 1 k, o stovinčios bangos koeficientas būti mažesnis nei 1,5. Disertacijoje yra pateikiami teoriniai elektrinio lauko pasiskirstymo bangolaidinėje sekcijoje su rezistorinio jutiklio jautriuoju elementu viduje modeliavimo baigtinių skirtumų laiko skalėje metodu rezultatai, kai jautrusis elementas yra talpinamas standartiniuose H tipo bangolaidžiuose WRD250 ir WRD840. Modeliavimo metu buvo ieškoma tokių jautriojo elemento matmenų ir savitosios varžos, kad rezistorinis jutiklis tenkintų aukščiau paminėtus reikalavimus. Disertacijoje taip pat aprašomi trijų skirtingų rezistorinių jutiklių, kurių optimalūs matmenys buvo surasti iš modeliavimo rezultatų, eksperimentiniai tyrimai. Buvo nustatytos šių jutiklių jautrio dažninės charakteristikos, jutiklių atsako signalo priklausomybė nuo mikrobangų galios ir stovinčios bangos koeficientas. Sujungus sukurtąjį jutiklį su plačiajuoste ruporine antena buvo atlikti mikrobangų galios tankio (elektrinio lauko stiprio) matavimai atviroje erdvėje. Pateikti disertacijoje internetinių maršrutizatorių ir šviesolaidinių konverterių elektromagnetinio atsparumo tyrimai, kuriuose rezistoriniai jutikliai naudojami elektrinio lauko stipriui... [toliau žr. visą tekstą]