A system has been developed to accurately detect phase produced in optical interferometric sensors. The system employs optical heterodyning and synchronously detects optical phase by feeding back an error signal to a phase modulator in the reference leg of the interferometer. This system is seen to have properties similar to a phase-locked loop used for the demodulation of FM signals. The system is modeled and found to be of second order and nonlinear. A linear approximation to the original model serves to accurately describe the system in synchronous operation and is corroborated with well matched empirical data. The nonlinear model is simulated via computer techniques and is used to describe the system's parameters that lead to loss and reacquisition of synchronization.

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A surface acoustic wave sensor based on an extrinsic Fabry-Perot interferometer is described. A single-mode fiber, used as the input/output fiber, and a multimode fiber, used mainly as a reflector, form an air-gap that acts as a low-finesse Fabry-Perot cavity. The Fresnel reference reflection from the glass/air interface at the front of the air-gap interferes with the sensing reflection from the air/glass interface at the far end of the air-gap in the input/output fiber. Strains in the silica tube housing the two fibers change the air-gap length, thereby altering the phase difference between the reference and sensing reflections and modulating the output intensity. A theoretical analysis of the interaction between the strain induced by the acoustic fields and the fiber sensor is presented. Because signal drifting in interferometric sensors is common, a dual optical wavelength stabilization technique is also incorporated into the sensor to minimize the effect. Signal to noise ratios (SNR’s) on the order of 39 dB are obtained with a strain sensitivity of 4°/ μstrain cm⁻¹. / Master of Science

Orientador: Antonio Carlos Ferreira Seridonio / Banca: Claudio Luiz Carvalho / Banca: Makoto Yoshida / Resumo: Investigou-se teoricamente um sistema composto por um interferômetro do tipo AharonovBohm com dois pontos quânticos, onde um deles encontra-se acoplado à um fio de Kitaev na fase topológica, nos casos em que se desconsidera a interação de Coulomb entre os pontos quânticos (caso não interagente) e quando a mesma é levada em conta (caso interagente). Na primeira situação, verificou-se a presença robusta da anomalia de voltagem zero para ambos os regimes de interferência Fano adotados. Além do mais, constatou-se que o estado de Majorana isolado possui uma maneira singular de quebrar a simetria dos perfis de densidade de transmitância em função da diferença simétrica de energia dos pontos quânticos e da energia de Fermi dos terminais metálicos. Tais perfis podem ser obtidos experimentalmente por medidas de condutância. Na situação de pontos quânticos interagentes em ressonância, verificou-se que a razão entre a magnitude da repulsão de Coulomb e o acoplamento fio-ponto quântico altera a largura da anomalia de voltagem zero em ambos os regimes Fano analisados. Esse fato sugere que a correlação eletrônica influencia o tempo de vida do estado de Majorana no ponto quântico hibridizado diretamente com o fio. Ademais, para a situação de pontos quânticos não ressonantes, a inversão dos valores de energia dos mesmos também modifica a largura da anomalia de voltagem zero, fenômeno que não ocorre para o caso não interagente. Acredita-se que o dispositivo proposto neste trabalho constitui um mecanismo experimental alternativo para detectar excitações de Majorana / Abstract: We investigate theoretically a setup composed by an Aharonov-Bohm-like interferometer with two quantum dots, where one of them is coupled to a Kitaev wire within the topological phase, which is explored in two cases: (i) the interdot Coulomb correlation is disregarded (noninteracting case) and (ii) the same is taken into account (interacting case). In the situation (i), we verify the presence of the zero-bias anomaly for the both Fano regimes of interference adopted. Furthermore, we found that an isolated Majorana state has a particular way of breaking the symmetry in transmittance profiles, which can be accessed experimentally by performing electrical conductance measurements. In the situation (ii), for interacting quantum dots in resonance, we notice that the ratio between the Coulomb repulsion strength and the wire-dot coupling changes the width of the zero-bias peak for both Fano regimes analyzed. This feature suggests that the electronic correlation modifies the Majorana state lifetime in the dot directly coupled to the wire. Moreover, for the off-resonance situation, the swap between the energy levels of the dots also changes the width of the Majorana peak, which is not observed in the noninteracting case. The results obtained here can guide experimentalists that pursuit a way of revealing Majorana signatures / Mestre

The culmination of a comprehensive experimental study of a number of nonlinear optical materials and their device applications. The optical phenomenology surrounding the interaction of laser radiation with these materials is emphasized. In addition to using interferometric techniques for their investigation and application, the overall theme of the research is the incorporation of interferometric descriptions of these interactions. Interference is commonly regarded to be the domain of linear optics; this work invalidates that notion. Nonlinear optics (NLO) is presented as simply a natural extension of linear optics. After a complete introduction to the general theory and relevant concepts required in the field of NLO, the first half of this manuscript presents a number of studies concerned with second-order nonlinear crystals for laser frequency conversion. The second half of this dissertation presents research on the nonlinear optical properties of semiconductors and semiconductor microstructures for optical-bistability-related applications. Optical bistability and related phenomena made possible using these materials in a nonlinear Fabry-Perot interferometer are stressed.

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No description available.

Since 1975 McCarthy and Low have conducted a program of Michelson spatial interferometry at infrared wavelengths, measuring a large number of evolved stars and protostellar objects. This dissertation discusses the development of an infrared speckle interferometer which was used to extend those observations. This instrument uses a modified version of the technique pioneered by Sibille, Chelli, and Lena. The secondary mirror is used to scan the image across a narrow slit. Each scan is fourier transformed, and the modulii squared of many such transforms are coadded. Both the object of interest and a point source are observed. The square root of the ratio of their power spectra is the visibility as defined by Michelson. This system was assembled for the most part with existing equipment and the design should be readily adaptable to other observatories. Initial tests were made with the 154 cm telescope of the University of Arizona since it had a preexisting mechanism for scanning the secondary. However most of the observations were carried out with the University's 229 cm telescope. A new linear servo was added to the existing hard-stop chopper for this telescope's f/45 secondary. Three detector systems were used to provide wavelength coverage from 2 to 12 microns. An N₂ cooled InSb and a He cooled bolometer were available from the Michelson program. In addition a high sensitivity He cooled InSb detector from the Steward Observatory FTS was used. Slits with an angular size of λ/2D, where D is the telescope diameter were placed at the focal plane in the dewar. The narrow slit results in diffraction losses when used with conventional dewar optics. The loss could be eliminated with optics optimized for this application. However even with the loss, a large number of objects could be observed. Test results at 2 microns were obtained for a double star, the asteroids Vesta and Ceres, and the Galilean satellites Ganymede and Callisto, The protostellar objects W3 IRS 5, S140, and Mon R2 IRS 3 were resolved. The separation, orientation, and relative brightness of the two components IRS 5 were measured at 5 microns. The separation is 1.26" ±0.06 and the position angle is 37° ±5. The brightness ratio is approximately 0.59. S140 and Mon R2 IRS 3 were observed at 2 microns. S140 shows some indication of an extended region of greater than 1" contributing half the flux. IRS 3 has a size of approximately 1" but the data is too noisy for an exact fit. Upper size limits were determined for BN, GL 490, GL 2591, and NGC 2264 IRS. A large number of evolved stars were observed. The size of the shell around Alpha Ori was found to be ∼4" at 11 microns. Observations were obtained for IRC + 10216 at 2, 5, 8, and 11 microns which further define the asymmetrical shape of this object. Observations were also obtained for VY CMa. Upper size limits were established for Omicron Ceti, IRC + 10011, RX Boo, R Hyd, W Hyd, and CIT 6.

No description available.

No description available.