The Nitrogen Phosphorus Detector is a sensitive, selective device used in gas chromatography. It responds selectively towards nitrogen and phosphorus containing organic compounds with detection limits in the picogram range. The detector is of great importance for the measurement of trace levels of drugs, pesticides and herbicides in biological matrices and the environment. There is, however, some dispute in the literature regarding the detector's response mechanism. The detector is based on a hydrogen-air diffusion flame. Two electrodes polarise the flame with a potential difference of about 200 V and the current through the flame is measured using an electrometer amplifier. The selectivity of the system relies on the presence of an alkali metal source, usually rubidium. In the presence of nitrogen- and phosphorus-containing organics, C~ and PO· anions are formed, yielding a current which is the measured response. It has been suggested that this selective response arises from a charge transfer reaction between the rubidium excited states and ~ or PO· and P02• radicals. Using an AlGaAs diode laser, the rubidium excited state population can be modulated and the influence on detector current monitored. Rubidium resonance-enhanced ionisation, laser-induced fluorescence and emission spectroscopy have all been used to further probe the response mechanism of the detector. Results have demonstrated that during response the C~ radical concentration increases. In addition the diode laser can modulate the excited state rubidium concentration altering it by a factor of 2. However despite more that doubling the Rubidium excited state concentration no increase in detector response is observed. From these observations it has been concluded that the above mentioned charge transfer reaction plays little if any role in detector response.

The effects of tension and compression applied to unbonded InGaAsP semiconductor diode lasers have been studied. A theoretical calculation of the stress distribution within the laser and an analysis of the effect of strain on optical gain in semiconductors is presented. The observed dependence of threshold, wavelength, and polarization of the laser output on the applied stress is explained in terms of the strain dependence of the valence-band wavefunctions. The polarization behaviour is found to be related to thermal stress and the structure of the device. A technique has been developed to measure the thermal stress induced by current heating at the 105 dynes/cm2 level. The effect of stress on the below threshold behaviour of the lasers was investigated. The results are consistent with the strain dependence of the TE and TM mode gains. / Thesis / Master of Engineering (ME)

Orientadores: Evandro Conforti, Cristiano de Melo Galle / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e Computação / Made available in DSpace on 2018-08-09T14:44:31Z (GMT). No. of bitstreams: 1 Guimaraes_Murilo_M.pdf: 2868472 bytes, checksum: 35d629f44273794bf3425431f0abbade (MD5) Previous issue date: 2007 / Resumo: O advento das comunicações por fibras ópticas esteve intrinsecamente ligado aos lasers a diodo semicondutor. Posteriormente, principalmente na área de redes metropolitanas, iniciaram-se as aplicações envolvendo o amplificador óptico a semicondutor (SOA, em inglês). O SOA é muito similar ao laser a diodo semicondutor, pois também amplifica a luz incidente através da emissão estimulada, a qual advém da emissão pelos portadores elétricos da região ativa. Estes são bombeados na região ativa através da corrente elétrica injetada na porta elétrica do SOA. A similaridade não é completa devido ao fato do amplificador não possuir realimentação de luz através de uma cavidade óptica ressonante, uma vez que sua região ativa é terminada por faces anti-refletivas. Dessa forma, a luz é amplificada apenas em uma passagem pela região ativa do SOA, sendo também denominado neste caso, SOA-TW, ou de onda caminhante. Desta forma, fazendo-se uma analogia com circuitos, a diferença SOAlaser é semelhante à diferença amplificador-oscilador eletrônico. Devido a esta semelhança, o estudo desenvolvido no presente trabalho, sobre o comportamento da impedância do amplificador óptico a semicondutor, foi baseado em um modelo equivalente de circuito de microondas desenvolvido para o laser a diodo semicondutor. O comportamento da impedância do SOA, composto por seu encapsulamento e chip, é de extrema importância para o controle e aprimoramento de chaveamento eletro-óptico do SOA em redes de última geração. Visando ao aprofundamento deste estudo, análises teóricas a respeito do laser a diodo semicondutor e do amplificador óptico a semicondutor são apresentados. Em seguida, são apresentados os resultados experimentais, com a extração do circuito equivalente do SOA e sua montagem eletro-óptica, com a comparação entre as respostas experimentais e teóricas. Nas considerações finais discutem-se as sugestões para trabalhos futuros sobre o comportamento da impedância eletro-óptica do SOA / Abstract: The advent of communications using optical fiber was always connected, intrinsically, with the semiconductor diode laser. Later, in metropolitan optical networks, the semiconductor optical amplifier (SOA) was introduced to amplify up to eight channels in a WDM (wavelength division multiplex) system. The semiconductor optical amplifier and the semiconductor laser diode are similar since both of them amplify the input light through stimulated emission, which result from electric carriers that are pumped in the active layer through the injection current in the electrical gate in these devices. The similarity is not complete since the SOA has anti-reflection coatings at the end emission faces. Therefore, the light is amplified by the active layer only in one pass; in this case the SOA is called TW SOA (traveling wave SOA). Due to the similarity between the devices, the present study of the SOA impedance behavior was based in an equivalent model from researches about microwave circuits used in the literature to analyze semiconductor diode lasers. The SOA impedance behavior is given by the chip itself and its package; it is important to control and to improve the electrical-optical switch using the SOA for next generation networks. Looking for a deep knowledge about this research, theoretical analyses of the semiconductor diode lasers and SOA was presented in this research. After it, the experimental results are showed with the extraction of the SOA equivalent circuit and the electrical-optical assembly, and the comparison between the experimental and theoretical results was done. At the end of this work, some suggestions for future works are proposed regarding the behavior of the SOA electrical-optical impedance / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica