In this study, we focus on the electric optical characteristic of guest/host polymer system. The charge transfer chromophore Wu182 which contain fluorine atom in it was mixed with polymer PMMA and solved in chloroform, while DR1/PMMA served as reference sample. The wu182/PMMA and DR1/PMMA thin films were produced by spin coating. The thin film was poled at the temperature above glass transition temperature until the second harmonic generation signal was present. The poled thin film was placed in one arm of Mach-Zehnder interferometer. Voltage modulation applied to the polymer films can cause phase changes in the interferometer from that we estimate the electro-optic coefficient. From our experiments, we found that modulating frequency had significant influence on the electro-optic effect. The result shows that Wu182 possess large nonlinear optical coefficient. The valid electro-optic coefficient r13 was obtained to be 2.620 pm/V when the frequency was above 6 kHz.

A montagem de um sistema que permite a detecção de modulação no coeficiente de absorção ótica, devido ao campo elétrico aplicado, foi concluída. A máxima sensibilidade atingida foi de &#916 K / K = 1,5 x 10-6 com resolução em comprimento de onda de 3 nm. O efeito Stark de 2&#170 ordem, na freqüência dupla da do campo elétrico aplicado foi medido para o centro F em KCl e KBr e comparado com provisões teóricas. Os valores obtidos para o KCl coincidem com os de Chiarotti, o que confirma o bom funcionamento do sistema, e diferem dos valores calculados teoricamente. Essa diferença é atribuída à correção do campo local. Os valores obtidos experimentalmente para a variação relativa do coeficiente de absorção foram: para KCl: &#916K / K = 2,93 x 10-5 (78&#176 K) para KBr: &#916K / K = 2,85 x 10-5 (78&#176 K) / The assembly of a system which allows the detection of modulation in the coefficient of optical absorption, due to the applied electrical field, was completed. The maximum sensitivity achieve was &#916 K / K = 1,5 x 10-6, in wave length, of 3 nm. The Stark effect of second order, in the frequency twice as that of the applied electrical field was measured for the center F in KCl and KBr and compared with theoretical previsions. The values obtained for KCl coincide with those of Chiarotti\'s, which confirms the good functioning of the system, and differ from the values calculated theoretically. This difference in ascribed to the correction of the local field. for KCl: &#916K / K = 2,93 x 10-5 (78&#176 K) for KBr: &#916K / K = 2,85 x 10-5 (78&#176 K).

A searched for narrow-band-noise (NBN) modulations of the infrared transmission in blue bronze has been performed. No modulations were observed, giving an upper limits for NBN changes in the absorption coefficient of )2000/(/3.0.andlt;.cmNBN. The implication of these results on proposed CDW properties and NBN mechanisms are discussed. An infrared microscope with a capability of doing both reflectance and transmission measurements has been integrated into the previous electro-transmission system with tunable diode lasers. Electro-optic experiments were done using the microscope for the studies of the CDW states of K0.3MoO3 (blue bronze) and orthorhombic TaS3. The electro-reflectance signal for blue bronze has been evidenced for the first time. The infrared reflectance of K0.3MoO3 varied with position when a voltage greater than the CDW depinning threshold is applied. The spatial dependence of .R/R was slightly different than for ./, in that the magnitude of .R/R decreased and, for low voltages and frequencies, the signal became inverted near the contacts. Perhaps the differences might be associated with changes in the CDW properties on the surface. For blue bronze, the electro-reflectance signal was measured to be smaller than electro-transmittance signal by one order of magnitude for light polarized transverse to the chain direction, while the electro-reflectance signal for parallel polarized light was found to be a few times smaller than for transverse polarized light. The fits of the electro-reflectance spectrum showed that the changes in background dielectric constant were ~ 0.05 % and/or oscillator strength and/or frequency shifts of the phonons were ~ 0.05 % and ~ 0.005 cm-1 in the applied electric field. We also found that parallel polarized phonons are affected by CDW strain, and these changes dominate the electro-reflectance spectrum. We have examined the electro-reflectance spectra associated with CDW current investigation for light polarized parallel to the conducting chains for signs of expected current-induced intragap states, and conclude that the density of any such states is at most a few times less than expected. We have observed a large (~1%) change in infrared reflectance of orthorhombic TaS3, when its CDW is depinned. The change is concentrated near one current contact. Assuming that the change in reflectance is proportional to the degree of CDW polarization, we have studied the dynamics of CDW repolarization through position dependent measurements of the variation of the electro-reflectance with the frequency of square wave voltages applied to the sample, and have found that the response could be characterized as a damped harmonic oscillator with a distribution of relaxation (i.e. damping) times. The average relaxation time, which increases away from the contacts, varies with applied voltage as with p ~ 3/2, but the distribution of times broadens as the voltage approaches the depinning threshold. Very low resonant frequencies (~ 1 kHz) indicate a surprisingly large amount of inertia, which is observable in the time dependence of the change in reflectance as a polarity dependent delay of ~ 100 s.

A montagem de um sistema que permite a detecção de modulação no coeficiente de absorção ótica, devido ao campo elétrico aplicado, foi concluída. A máxima sensibilidade atingida foi de &#916 K / K = 1,5 x 10-6 com resolução em comprimento de onda de 3 nm. O efeito Stark de 2&#170 ordem, na freqüência dupla da do campo elétrico aplicado foi medido para o centro F em KCl e KBr e comparado com provisões teóricas. Os valores obtidos para o KCl coincidem com os de Chiarotti, o que confirma o bom funcionamento do sistema, e diferem dos valores calculados teoricamente. Essa diferença é atribuída à correção do campo local. Os valores obtidos experimentalmente para a variação relativa do coeficiente de absorção foram: para KCl: &#916K / K = 2,93 x 10-5 (78&#176 K) para KBr: &#916K / K = 2,85 x 10-5 (78&#176 K) / The assembly of a system which allows the detection of modulation in the coefficient of optical absorption, due to the applied electrical field, was completed. The maximum sensitivity achieve was &#916 K / K = 1,5 x 10-6, in wave length, of 3 nm. The Stark effect of second order, in the frequency twice as that of the applied electrical field was measured for the center F in KCl and KBr and compared with theoretical previsions. The values obtained for KCl coincide with those of Chiarotti\'s, which confirms the good functioning of the system, and differ from the values calculated theoretically. This difference in ascribed to the correction of the local field. for KCl: &#916K / K = 2,93 x 10-5 (78&#176 K) for KBr: &#916K / K = 2,85 x 10-5 (78&#176 K).

<p> Lithium niobate has interesting characteristics such as the electro-optic effect, the acousto-optic effect, piezoelectricity and large nonlinear optical coefficients. Potential applications in MEMS field could be explored if microstructures are fabricated in lithium niobate substrates,. This thesis presents the fabrication and characterization of a lithium niobate MEMS device. As lithium niobate crystal is difficult to process using standard semiconductor techniques including both wet etching and dry etching, new methods are required to process lithium niobate. In our project, picosecond laser pulses were chosen to produce bridges on lithium niobate. Fabrication of grooves with high aspect ratio were attempted and grooves with clean morphology were obtained when laser pulses with low cutting speed, medium pulse energy, and large number of passes were employed. This shows picosecond laser machining is a viable method to process lithium niobate.</p> <p> Waveguides in Z cut lithium niobate crystal were fabricated using Ti-indiffusion techniques. After the fabrication of waveguides in lithium niobate, a SiO2 film with a thickness of 0.3μm was deposited as a buffer layer. Ti-Pt-Au electrodes for actuation function were then deposited through lift-off technique. Finally a bridge structure (80um in width and 600um in length) with a waveguide embedded in it was fabricated with picosecond laser. The insertion loss before and after laser machining was 6.99dB and 5.01dB respectively.</p> <p> Optical and electrical tests were performed in an effort to determine the resonance frequency of bridge. In the optical test, many bulk piezoelectric resonance peaks were presented in the frequency spectrum. After damping the vibration of substrate, these spikes disappeared and only a background noise with small spikes were obtained. As those small spikes are not reproducible, the optical test is not a viable method to determine resonance frequency of the bridge structure in our device. The electrical test was then carried out in a vacuum environment in order to find the resonance frequency. The spectrum presents a spike with large amplitude. However, the phase and amplitude of the spike remained the same when the vacuum condition was removed, which indicates the spike is not related to the resonance of the bridge. In summary, the resonance frequency of bridge structure could not be determined by these two approaches.</p> <p> Future work could involve directly investigating the material properties surrounding the machining region to see whether the piezoelectricity of the material has been damaged from laser ablation process. New laser machining process of lithium niobate may also need to be studied to avoid this damage to the substrate structure. Even though our device could not be driven to vibrate at its resonance frequency, it is worth making microstructures in lithium niobate substrates. The combination of optical, mechanical and electrical elements will make lithium niobate a great potential material for optical MEMS applications.</p> / Thesis / Master of Applied Science (MASc)

Orientador: Cláudio Kitano / Banca: Ricardo Tokio Higuti / Banca: Luiz Antonio Perezi Marçal / Resumo: Neste trabalho estuda-se a interferometria laser, a qual constitui uma técnica adequada para determinar grandezas físicas com sensibilidade extremamente elevada. Basicamente, no interferômetro óptico, a informação a respeito do dispositivo sob teste é inserida na fase da luz. Utilizando-se o fotodiodo, promove-se a transferência de informação, do domínio óptico para o elétrico, no qual pode ser demodulada usando-se as várias técnicas disponíveis na literatura para detectar sinais modulados em fase. Ênfase é dada a um novo método de demodulação de fase óptica auto-consistente e de grande sensibilidade. Neste método, utiliza- se a modulação dada por uma forma de onda triangular e é baseado na análise do espectro do sinal fotodetectado, sendo capaz de estender a faixa dinâmica de demodulação a valores tão elevados quanto às dos métodos clássicos. Simulações dinâmicas computacionais de interferômetros ópticos são executadas em Simulink juntamente com este método, levando-se em consideração tensões de ruído eletrônico do tipo ruído branco, evidenciando a eficiência do método quando comparados com dados teóricos obtidos em Matlab. A validação experimental do método é realizada com o auxílio de um modulador eletro-óptico de amplitudes, cujas características de fase podem ser previstas analiticamente. Trata-se de um sensor polarimétrico baseado em cristal de Niobato de Lítio, em que a diferença de fase óptica induzida pela tensão elétrica aplicada pode ser determinada através de análise espectral, tal como o novo método descrito neste trabalho. Um interferômetro de Michelson homódino de baixo custo é implementado e a eficiência do novo método de demodulação de fase óptica é avaliada através de testes com atuadores e manipuladores piezoelétricos flextensionais, cujas características de linearidade são conhecidas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, has been done a study the laser interferometer, which is a technique for determining physical quantities with extremely high sensitivity. Basically, in the optical interferometer, information about the device under test modulates the phase of light. Using a photodiode, promotes the transfer of information from the optical domain for the electric, which can be demodulated using the various techniques available in literature to detect modulated signals in phase. Emphasis is given to a new method of phase demodulation of optical self-consistent and high sensitivity. The method employs a linear modulation given by a triangular waveform, and is based on analysis of the spectrum of the photodetected signal, being able to extend the dynamic range of the demodulation values as high as the classical methods. Dynamic computational simulations of optical interferometers are implemented in Simulink with this method, taking into account strains of electronic noise like white noise, indicating the efficiency of the method compared with theoretical data obtained in Matlab workspace. The experimental validation of the method is performed with the aid of an electro- optic amplitude modulator, whose phase characteristics can be analytically predicted. This is a polarimetric sensor based on lithium niobate crystal, in which the optical phase difference induced by electric voltage can be determined by spectral analysis, using new method described in this work. A low cost homodyne Michelson interferometer is implemented and the efficiency of the new method of optical phase demodulation is evaluated by testing with piezoelectric flextensional actuators whose characteristics of linearity are well known.The experimental results agree with theoretical analysis and reveal this method is more efficient than the classical methods / Mestre

Optical parametric oscillators (OPOs) and optical parametricamplifiers (OPAs) constitute a class of optical frequencyconverting devices that have many possible applications, e.g.in range finding, molecular spectroscopy and medicine. They canconvert the frequency of the incident pump field with highefficiency, and generate two waves at new frequencies that willbe continuously tuneable over a wide spectral range. Virtuallyany wavelengths within the transparency region of the nonlinearmaterial can be generated if the material can bequasi-phasematched (QPM). In addition, QPM gives thepossibility to utilise the largest nonlinear tensor element ofthe material and allows walk-off free interaction between thewaves. The aims of this thesis have been to investigate thepossibility to use QPM KTiOPO4crystals as nonlinear material in nanosecond OPOsand OPAs operating at room-temperature, and to explore theadvantages and shortcomings of these devices. The technique ofelectric field poling has been employed to implement the QPMstructure in flux grown KTiOPO4(KTP). The main conclusion is that periodically poled KTP (PPKTP)is a suitable material to use in nanosecond OPOs and OPAs. Thematerial properties that foremost make KTP into an attractivenonlinear material are: The large value of the nonlinearcoefficient d33, the high resistance to optically inducedbreakdown, the low susceptibility to grey-track formation, theinsensitivity to the photorefractive effect, the widetransparency and the low coercive field. The thesis shows that it is possible to pole large volumesof KTP with a high quality of the QPM structure. Highlyefficient nanosecond OPOs have been constructed during thisproject. Maximum conversion efficiencies have reached 45 % inthe case of a singly resonant OPO (SRO) built around a 3 mmthick PPKTP crystal. Total pulse energies for both the signal(1.72 µm) and the idler (2.8 µm) of up to 18 mJ wasreached and an average output power of 2 W was obtained forthis sample. However, up to 24 W was produced in a doublyresonant OPO operating close to degeneracy. The efficiencyreached 48 % for that case. Truly continuous and very widespectral tuning has also been demonstrated, as well as a narrowbandwidth OPO operating on one single longitudinal mode. <b>Keywords:</b>optical parametric oscillators, opticalparametric amplifiers, quasi-phasematching, KTiOPO4, nonlinear optics, frequency conversion, periodicelectric field poling, ferroelectrics, high-order secondharmonic generation, electro-optic effect.

<p>Optical parametric oscillators (OPOs) and optical parametricamplifiers (OPAs) constitute a class of optical frequencyconverting devices that have many possible applications, e.g.in range finding, molecular spectroscopy and medicine. They canconvert the frequency of the incident pump field with highefficiency, and generate two waves at new frequencies that willbe continuously tuneable over a wide spectral range. Virtuallyany wavelengths within the transparency region of the nonlinearmaterial can be generated if the material can bequasi-phasematched (QPM). In addition, QPM gives thepossibility to utilise the largest nonlinear tensor element ofthe material and allows walk-off free interaction between thewaves.</p><p>The aims of this thesis have been to investigate thepossibility to use QPM KTiOPO₄crystals as nonlinear material in nanosecond OPOsand OPAs operating at room-temperature, and to explore theadvantages and shortcomings of these devices. The technique ofelectric field poling has been employed to implement the QPMstructure in flux grown KTiOPO₄(KTP).</p><p>The main conclusion is that periodically poled KTP (PPKTP)is a suitable material to use in nanosecond OPOs and OPAs. Thematerial properties that foremost make KTP into an attractivenonlinear material are: The large value of the nonlinearcoefficient d₃₃, the high resistance to optically inducedbreakdown, the low susceptibility to grey-track formation, theinsensitivity to the photorefractive effect, the widetransparency and the low coercive field.</p><p>The thesis shows that it is possible to pole large volumesof KTP with a high quality of the QPM structure. Highlyefficient nanosecond OPOs have been constructed during thisproject. Maximum conversion efficiencies have reached 45 % inthe case of a singly resonant OPO (SRO) built around a 3 mmthick PPKTP crystal. Total pulse energies for both the signal(1.72 µm) and the idler (2.8 µm) of up to 18 mJ wasreached and an average output power of 2 W was obtained forthis sample. However, up to 24 W was produced in a doublyresonant OPO operating close to degeneracy. The efficiencyreached 48 % for that case. Truly continuous and very widespectral tuning has also been demonstrated, as well as a narrowbandwidth OPO operating on one single longitudinal mode.</p><p><b>Keywords:</b>optical parametric oscillators, opticalparametric amplifiers, quasi-phasematching, KTiOPO₄, nonlinear optics, frequency conversion, periodicelectric field poling, ferroelectrics, high-order secondharmonic generation, electro-optic effect.</p>

Made available in DSpace on 2014-06-11T19:22:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-11-30Bitstream added on 2014-06-13T20:49:10Z : No. of bitstreams: 1 takiy_ae_me_ilha.pdf: 1702331 bytes, checksum: b89d2b4960ee7bbc0e01a3a5d3e7a2be (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Neste trabalho estuda-se a interferometria laser, a qual constitui uma técnica adequada para determinar grandezas físicas com sensibilidade extremamente elevada. Basicamente, no interferômetro óptico, a informação a respeito do dispositivo sob teste é inserida na fase da luz. Utilizando-se o fotodiodo, promove-se a transferência de informação, do domínio óptico para o elétrico, no qual pode ser demodulada usando-se as várias técnicas disponíveis na literatura para detectar sinais modulados em fase. Ênfase é dada a um novo método de demodulação de fase óptica auto-consistente e de grande sensibilidade. Neste método, utiliza- se a modulação dada por uma forma de onda triangular e é baseado na análise do espectro do sinal fotodetectado, sendo capaz de estender a faixa dinâmica de demodulação a valores tão elevados quanto às dos métodos clássicos. Simulações dinâmicas computacionais de interferômetros ópticos são executadas em Simulink juntamente com este método, levando-se em consideração tensões de ruído eletrônico do tipo ruído branco, evidenciando a eficiência do método quando comparados com dados teóricos obtidos em Matlab. A validação experimental do método é realizada com o auxílio de um modulador eletro-óptico de amplitudes, cujas características de fase podem ser previstas analiticamente. Trata-se de um sensor polarimétrico baseado em cristal de Niobato de Lítio, em que a diferença de fase óptica induzida pela tensão elétrica aplicada pode ser determinada através de análise espectral, tal como o novo método descrito neste trabalho. Um interferômetro de Michelson homódino de baixo custo é implementado e a eficiência do novo método de demodulação de fase óptica é avaliada através de testes com atuadores e manipuladores piezoelétricos flextensionais, cujas características de linearidade são conhecidas... / In this work, has been done a study the laser interferometer, which is a technique for determining physical quantities with extremely high sensitivity. Basically, in the optical interferometer, information about the device under test modulates the phase of light. Using a photodiode, promotes the transfer of information from the optical domain for the electric, which can be demodulated using the various techniques available in literature to detect modulated signals in phase. Emphasis is given to a new method of phase demodulation of optical self-consistent and high sensitivity. The method employs a linear modulation given by a triangular waveform, and is based on analysis of the spectrum of the photodetected signal, being able to extend the dynamic range of the demodulation values as high as the classical methods. Dynamic computational simulations of optical interferometers are implemented in Simulink with this method, taking into account strains of electronic noise like white noise, indicating the efficiency of the method compared with theoretical data obtained in Matlab workspace. The experimental validation of the method is performed with the aid of an electro- optic amplitude modulator, whose phase characteristics can be analytically predicted. This is a polarimetric sensor based on lithium niobate crystal, in which the optical phase difference induced by electric voltage can be determined by spectral analysis, using new method described in this work. A low cost homodyne Michelson interferometer is implemented and the efficiency of the new method of optical phase demodulation is evaluated by testing with piezoelectric flextensional actuators whose characteristics of linearity are well known.The experimental results agree with theoretical analysis and reveal this method is more efficient than the classical methods

Notre recherche porte sur la réponse optique des nanostructures et nous sommes certainement intéressés à la modélisation de ces structures afin d'améliorer le confinement de la lumière. Ce confinement est un des paramètres qui conduisent à l'exaltation des effets optique linéaires et non linéaires, simultanément. Notre travail est divisé en deux sections, qui présentent deux effets optiques diffèrents basées sur le confinement des champs à l’intérieur du structure. Dans la première section, la réponse optique d’une nano-antenne à ouverture en forme de nœud papillon (BNA : Bowtie nano-aperture) sera étudiée en fonction de l’indice de réfraction du milieu. L’étude discute la variation de la longueur d’onde de résonance ainsi que l’intensité du champ confiné au milieu du gap de la BNA en fonction de la distance qui sépare l’antenne d’un substrat placé en face. L’étude prend le cas d’une BNA gravée au bout d’une fibre optique métallisée. Une étude numérique complète a été réalisée par des simulations numériques basées sur la méthode des différences finies FDTD-3D (Finite Difference Time Domaine – Three dimension). Le code utilisé est développé au sein du département d’Optique de l’Institut FEMTO-ST. Notre modèle numérique décrits bien la géométrie de l’antenne ainsi que la pointe. De même les propriétés optiques de la couche métallique de la sonde sont bien décrites à travers un modèle de dispersion (model de Drude). Une étude expérimentale a été réalisée en plus pour une validation des résultats collecte théoriquement, l’étude a considéré le cas de deux BNA avec des paramètres géométrique différents, néanmoins les résultats obtenues se correspond fortement aux résultats obtenues numériquement. Dans la deuxième partie, l'effet électro-optique des nanostructures sera étudié. L’effet électro-optique ou effet Pockels consiste d’une variation linéaire de l'indice de réfraction d'un milieu non-linéaire en fonction d'un champ électrique extérieur. Cependant, la variation est reliée au tenseur de susceptibilité non linéaire du deuxième ordre, ainsi, cette effet ce produit seulement dans les matériaux non-centrosymétrique. Dans notre étude les nanostructures sont fabrique avec le Niobate de Lithium (LN) qui est considéré comme le plus avantageux diélectrique pour l’exaltation des effets non linéaire grâce à ces propriétés (acousto-optique, électro-optique, piézoélectrique …). L’étude est complétée numériquement garce a des simulations basées sur la FDTD en tenant compte de la polarisation du champ. Au début, une validation de l’utilisation de la FDTD pour estimer l’effet électro-optique intrinsèque du LN a été achevée, l’étude considère un milieu homogène (pas de confinement des champs dans le milieu) qui a pour indice de réfraction celle du LN. Pour des structure qui présentes un confinement du champ plusieurs approximation ont été suggère dans cette partie. En outre, nous présentons un nouveau modèle auto-cohérent dans lequel la variation de l'indice de réfraction est modifiée au cours de la simulation. Plusieurs structure ont été discutés (réflecteur de Bragg, structure à cavité et 2D cristal photonique) qui présentent des facteurs de confinement différents. Une étude comparative entre les différentes méthodes, montre que la différence entre les résultats de chaque hypothèse devient plus important proportionnellement au facteur de confinement. / Our research is concerned with the optical response of nano-structures by modeling them in order to enhance the confinement of light in these structures, which leads to the exaltation of linear and nonlinear optical effects.Our work is divided into two sections, which are based on the enhancement of the electric field inside the structure. In the first section, we study the optical properties of a Bowtie Nano-aperture, BNA, as a function of the refractive index of the surrounding medium. The study discusses the variation of the resonance wavelength and the intensity of the enhanced field in the gap of the BNA as a function of the distance from a sample placed in front of our BNA. The BNA is engraved at the apex of a metallic coated fiber tip. In this section a theoretical study was achieved using the Finite Difference Time Domain method FDTD in which we implement a Drude dispersion model to faithfully describe the optical properties of metals. In addition, a validating experimental study was achieved and a high accordance between both results is recorded.In the second section, the electro optical effect of nano-structures is studied. Electro-optical effect or Pockels effect is the variation of the refractive index of a nonlinear media as a function of an applied external electric field. The electro-optical effect is a linear variation of the media refractive index. However it is also related to the second order nonlinear susceptibility tensor, thus it becomes a nonlinear effect that only occurs in non-centrosymetric material. In our study we chose the case of a nano-structure fabricated with Lithium Niobate. Lithium Niobate is widely used in photonic applications due to its electro-optical, acousto-optical and nonlinear optical properties. We present a theoretical study of the electro-optical effects using the FDTD simulation method. We started by approving the ability to use the FDTD to calculate the refractive index variation in bulk Lithium Niobate then we suggest different approximations to estimate the refractive index variation when the light is confined inside the structure. In addition we suggest a new self-consistent method in which the variation of the refractive index is modified during the simulation. The study shows a comparison between different assumptions (used in previous research) and the self-consistent method for various structures, like Bragg reflectors, cavity structures and 2D photonic crystals. The study shows that the difference between the results of each assumption becomes greater when the optical confinement in the structure becomes more important.