Daniele M. Costantini

Efficient miniature fiber-optic tunable filter based on intracore Bragg grating and electrically resistive coating

An electrically tunable reflection filter based on a platinum-coated single-mode optical fiber that contains an intracore Bragg grating has been demonstrated. The device shows a dc tuning range of 2.15 nm with a corresponding electrical power of 0.54 W. Wavelength modulation (WM) has been observed at frequencies lower than 100 Hz. The wavelength shift depends linearly on the electrical input power. A maximum efficiency of 4.1 nm/W is obtained for dc tuning.

Tunable loss filter based on metal-coated long-period fiber grating

An all-fiber electrically tunable loss filter that is based on photoinduced long-period grating coated by Ti-Pt metal coating was developed and investigated. Maximum wavelength tuning of 11 nm with an applied power of 0.67 W was achieved for the HE17 cladding mode resonance peak.

In situ Strain and Temperature Monitoring of Adaptive Composite Materials

An optical fiber sensor is designed to simultaneously measure strain and temperature in an adaptive composite material. The sensor is formed by splicing two fiber Bragg gratings (FBGs) close to each other, which are written in optical fibers with different core dopants and concentrations. Their temperature sensitivities are hence different. The sensor is tested on an adaptive composite laminate made of unidirectional Kevlar-epoxy prepreg plies. Several 150 μm diameter prestrained NiTiCu shape memory alloy (SMA) wires are embedded in the composite laminate together with one fiber sensor. Simultaneous monitoring of strain and temperature during the curing process and activation in an oven is demonstrated.

Fiber amplifiers for coherent space communication

We report on the application of double-clad doped fiber amplifiers for coherent space communication systems using a master oscillator power amplifier (MOPA) design at 1.06 /spl mu/m. The master oscillator is either a single-frequency Nd:YAG solid-state laser or a distributed-feedback fiber laser. The power amplifier is a diode-laser-pumped double-clad Nd doped fiber with polarization control, 20 dB gain, and about 1.3 W output power. A dual stage configuration using a solid-state Nd:YAG amplifier as second stage is presented as well, increasing the output power to 3.5 W with 28 dB gain. We also report on the possibility to integrate a single-frequency fiber laser, an all-fiber phase modulator, and a fiber amplifier to build an all-fiber phase-modulated MOPA. Up to 1 W continuous-wave output phase-modulated with a bandwidth of 196 MHz has been achieved.

Stable and widely tunable all-fiber Pr(3+)-doped cw laser system using fiber Bragg gratings.

A simple and strictly all-fiber 1300-nm cw laser is presented. It is tunable over 16 nm with 0.5-nm linewidth and several milliwatts of output power in the whole tuning range from 1292 to 1308 nm. The setup uses a fiber Bragg grating as a combined tuning element and narrow-band output mirror. The simplicity and stability of this system are due to the following two characteristics: First, polarization control is not necessary anywhere in the system, and second, a wavelength-selective system and a narrow-band mirror are combined into one novel fiber-optic element.

In situ simultaneous strain and temperature measurement of adaptive composite materials using a fiber Bragg grating based sensor

An optical fiber sensor to simultaneously measure strain and temperature was designed and embedded into an adaptive composite laminate which exhibits a shape change upon thermal activation. The sensor is formed by two fiber Bragg gratings, which are written in optical fibers with different core dopants. The two gratings were spliced close to each other and a sensing element resulted with Bragg gratings of similar strain sensitivity but different response to temperature. This is due to the dependence of the fiber thermo-optic coefficient on core dopants and relative concentrations. The sensor was tested on an adaptive composite laminate made of unidirectional Kevlar-epoxy pre-preg plies. Several 150μm diameter pre-strained NiTiCu shape memory alloy wires were embedded in the composite laminate together with one fiber sensor. Simultaneous monitoring of strain and temperature during the curing process and activation in an oven was demonstrated.

All-fiber phase-modulated master oscillator power amplifier for coherent communication

An all-fiber phase-modulated master oscillator power amplifier for free-space coherent communication is presented. A distributed-feedback fiber laser at 1.06 /spl mu/m is used as master oscillator. A novel phase modulator based on a ZnO-coated single-mode fiber modulates the single frequency communication signal. The modulated signal is then amplified in a double-clad doped fiber power amplifier. Up to 1 W cw single-frequency output power, phase modulated at 196 MHz, has been obtained.

Applications of Active Thin Film Coatings on Optical Fibers

Keywords: [OFD] Reference LOA-CONF-1997-009View record in Web of Science Record created on 2009-07-20, modified on 2017-05-10

All-fiber phase modulator based on lead zirconate titanate thin-film coating

An all-fiber phase modulator based on lead titanate zirconate coating deposited by dc reactive magnetron sputtering was fabricated and optically characterized. The frequency response showed a flat broadband structure up to 600 kHz, with an efficiency of 0.73 rad/(V m). This is an order of magnitude higher than that for sputtered zinc oxide based phase modulators. Radial mode resonance peaks were observed between 10 and 700 MHz, with a maximum phase modulation amplitude of 0.3 rad at the fundamental radial resonance frequency of 25.6 MHz.

Influence of the deposition temperature and Pb species flux on the characteristics of PbTiO3 thin films deposited by sputtering on optical fibers

Integrated optical devices can be fabricated by the deposition of an electrode/piezoelectric/electrode multilayer thin film structure onto optical fibers, The particular structure used in this work is Au/PbTiO3/Pt/Ti, where the PbTiO3 is deposited by DC reactive magnetron sputtering at high temperature to obtain in situ crystallised perovskite structure. Preliminary studies showed that the deposition temperature and the relative fluences of the Pb and Ti species are determining parameters for the growth of phase pure perovskite PbTiO3. This study shows the effect of both parameters on the resulting film. The occurrence of a self-stabilising region for the growth of pure perovskite phase PbTiO3 has been observed. The maximal achievable dielectric constant depends on the relative Pb flux used. It increases with increasing PbO to TiO2 fluxes ratio. X-ray, microstructure, conductivity results and optical response of the devices are also briefly presented. An optical phase shift of 0.4 mrad/V has been measured for low frequency electrical excitation.