Rogério M. Cazo

Analysis of strategies to improve the directionality of square lattice band-edge photonic crystal structures

Recently, photonic crystal band-edge structures have been analyzed in the literature. However, most devices that have been presented so far emit light in different directions. We present a modal analysis (no gain included) of a few schemes to improve the directionality of these devices, i.e., in such a way that light that exits from them will travel mainly in a certain direction, eventually coupling its energy to a wide waveguide.

Fiber Bragg grating based angular accelerometer: a first approach

This paper shows the first results we obtained for angular acceleration sensing using a fiber Bragg grating based angular accelerometer (FBGAA). We present measurements of angular accelerations imposed by an oscillating plate. Post processed moving average was used to reduce structural natural oscillation noises. Key structural mounting ideas are shown.

Six Degree Freedom Optical Fiber Accelerometer

Linear accelerations measurements are needed in many applications, as industry, military, aircrafts, space navigation, robotics and others. Actually, the most usual solutions to measure linear accelerations are three piezoelectric sensors used in orthogonal mounting, or MEM’s sensors chips. Angular accelerations also are interesting to control and stabilize structures, like satellites and servo motors. It is possible to measure angular accelerations in two ways: direct measurement (using special sensors), or indirect measurements (obtaining acceleration of the angular velocity information) [1]. This work intends to present the structural and optical requirements of a six degree freedom opto‐mechanical accelerometer based on fiber Bragg grating (FBG). With this sensor, it will be possible the direct measurement of three axial accelerations, and of three angular accelerations, with unlimited rotation angle, using one single proof mass. The FBG’s are used as strain sensors and sustaining elements of the proof mass in the structure. Simulations have demonstrated that cross influences of 10 parts per million at worst case are possible. This kind of accelerometer may be used in navigation control, structural monitoring, satellite stabilization, guidance control and harsh environments, for example. The project requirements include the wavelength of FBG’s, pre‐strain and length of active segment of optical fibers, dimensions, material and structure of inertial proof mass and position of the fibers in the sustaining structureLinear accelerations measurements are needed in many applications, as industry, military, aircrafts, space navigation, robotics and others. Actually, the most usual solutions to measure linear accelerations are three piezoelectric sensors used in orthogonal mounting, or MEM’s sensors chips. Angular accelerations also are interesting to control and stabilize structures, like satellites and servo motors. It is possible to measure angular accelerations in two ways: direct measurement (using special sensors), or indirect measurements (obtaining acceleration of the angular velocity information) [1]. This work intends to present the structural and optical requirements of a six degree freedom opto‐mechanical accelerometer based on fiber Bragg grating (FBG). With this sensor, it will be possible the direct measurement of three axial accelerations, and of three angular accelerations, with unlimited rotation angle, using one single proof mass. The FBG’s are used as strain sensors and sustaining elements of the proo...

Analysis of some photonic crystal structures by using Bloch wave expansion

In this paper, some photonic crystal structures are analyzed by using MITs MPB software. This software uses a Bloch-wave expansion to obtain the band diagrams for the devices. The band diagrams for a few examples are analyzed based upon the results of this numerical method.

Experimental study of a multimode fiber Bragg grating temperature sensor

Initially, we have inscribed a uniform fiber Bragg grating in a multimode fiber. It was observed that the phase matching condition was approximately satisfied by a few modes, causing the appearance of lateral lobes. We have experimentally analyzed the dependence of these lobes upon variations in temperature. This study may lead to the construction of multimode temperature sensors.

A high nonlinearity elliptical fiber for applications in Raman and Brillouin sensors

Raman and Brillouin effects have found special applications in distributed sensing for smart materials and structures. In these sensors, the fiber acts as a distributed sensor, sensing strain and temperature over a range of tens of kilometers and, at the same time, carries this information to the installation that will process them. In order to optimize the fiber to operate under the Brillouin and Raman regimes, a special elliptical fiber with small effective area has been designed, which will allow these sensors to cover longer distances and/or employ lower power lasers.