Characterization of longitudinal acoustic waves in a fiber using an extrinsic Fabry-Perot interferometer

Longitudinal acoustical modes propagating in a fiber are characterized using an extrinsic Fabry-Perot interferometer. The method allows the detection of the fiber axial deflection peaks which correspond to the acoustic resonances. The method can be further used for estimating properties of acoustic excited fibers, such as acoustic frequency and wavelength, which are essential in the design of acousto-optic devices employing Bragg gratings

Fiber Fabry-Perot interferometer sensor for measuring resonances of piezoelectric elements

The development of a fiber extrinsic Fabry-Perot interferometer for measuring vibration amplitude and resonances of piezoelectric elements is reported. The signal demodulation method based on the use of an optical spectrum analyzer allows the measurement of displacements and resonances with high resolution. The technique consists basically in monitoring changes in the intensity or the wavelength of a single interferometric fringe at a point of high sensitivity in the sensor response curve. For sensor calibration, three signal processing techniques were employed. Vibration amplitude measurement with 0.84 nm/V sensitivity and the characterization of the piezo resonance is demonstrated

Multi-wavelength reflection spectra from an acousto-optic modulated fiber Bragg grating in a highly birefringent suspended core fiber

The interaction of a fiber Bragg grating and longitudinal acoustic waves in a highly birefringent suspended-core fiber is investigated for the realization of a multi-wavelength reflection property. The modulated grating couples power from the fast and slow polarization modes to shifted superposed modes supported by the grating. The grating reflectivity of the superposed modes are tuned by the voltage of an electrical signal. Up to five different wavelength reflection peaks have been generated indicating new possibilities for compact and fast fiber-integrated multi-wavelength dynamic filters

Electrically Tunable Multiwavelength Bragg Grating Filter Acoustically Induced in a Highly Birefringent Suspended Core Fiber

Multiwavelength reflection spectra induced by an acoustically modulated fiber Bragg grating (FBG) in a highly birefringent suspended core fiber are experimentally investigated. Longitudinal acoustic waves interacting with a grating generate side lobes in the reflectivity spectrum and produce a superposed reflection band. The reflectivity of up to five wavelength peaks can be actively tuned by the voltage of the electrical signal inducing the acoustic waves. This indicates new possibilities for compact and fast multiwavelength dynamic and fiber-integrated reflection filters

Proposta de Estudo de Função Mediada pelo GeoGebra

O trabalho aqui apresentado é resultado de uma pesquisa de Mestrado e teve como objetivo verificar se construções dinâmicas no GeoGebra, aplicadas em uma sequência de atividades facilitam a aprendizagem de função. Construções presentes no Imagiciel, um ambiente computacional de pesquisadores franceses, foram reconstruídas no GeoGebra e organizadas em uma sequência de atividades inspiradas na dialética ferramenta-objeto e aplicadas a alunos do primeiro ano do Ensino Médio. Como metodologia foram utilizados elementos da Engenharia Didática. Pela análise das respostas, pela interação entre os alunos e com as construções elaboradas no GeoGebra, em forma de applet’s, verificou-se que as atividades facilitaram a aprendizagem de função, em especial, o de função definida por sentenças em intervalos reais

Reflectivity and Bandwidth Modulation of Fiber Bragg Gratings in a Suspended Core Fiber by Tunable Acoustic Waves

The acousto-optic modulation of fiber Bragg gratings in a four-hole suspended core fiber is experimentally demonstrated. Strong modulations with a reflectivity amplitude decrease by up to 67% and a 57% bandwidth increase in the Bragg resonance are obtained for gratings of 0.26- and 1-nm 3-dB bandwidths, respectively. The reduction of the required acoustic power for achieving the acousto-optic modulation compared to conventional solid-core single-mode fibers points to more efficient modulator devices in suspended core fibers

Graphene Based Sensors for Air Quality Monitoring - Preliminary Development Evaluation

Indoor air pollution can induce adverse health effects on building occupants and pose a significant role in health worldwide. To avoid such effects, it is extremely important to monitor and control common indoor pollutants such as CO2, VOCs and relative humidity. Therefore, this work focuses on recent advances in the field of graphene-based gas sensors, emphasizing the use of modified graphene that broadly expands the range of nanomaterials sensors. Graphene films were grown on copper by chemical vapor deposition (CVD) and transferred to arbitrary substrates. After synthesis, the samples were functionalized with Al2O3 by ALD and characterized by a large set of experimental techniques such as XPS, Raman and SEM. The results demonstrated that graphene was successfully synthesized and transferred to SiO2, glass and polymer. As a proof-of-concept, ALD of Al2O3 was performed on the graphene surface to produce a graphene/metal oxide nanostructure towards the development of nanocomposites for gas sensing. From this perspective, a laboratory prototype device based in measuring the electrical properties of the graphene sample as a function of the gas absorption is under development

Bio-electrospraying of chondrocytes for cartilage tissue enginnering applications

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All-fiber laser mode-locked by the acousto-optic modulation of a fiber Bragg grating in suspended core fiber

An ytterbium-doped fiber laser mode-locked by the interaction of a fiber Bragg grating and longitudinal acoustic waves in a suspended core fiber is experimentally investigated. An optimized design of an acousto-optic modulator is also proposed. The results indicate output pulses with a width of less than 550 ps at a repetition rate of 10 MHz. The reduction of the power consumed by the transducer and the grating length points out to more efficient, compact and fast acousto-optic modulators for mode-locked all-fiber lasers

Electrosprayed cells proliferative behaviour in a 3d microporous scaffold

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