Jacques Albert

Apodization technique for fiber grating fabrication with a halftone transmission amplitude mask

Experimental results of fiber Bragg gratings fabricated with halftone amplitude transmission masks and 10-cm-long phase masks are presented for the first time to our knowledge. The performance of the devices is evaluated in terms of their spectral characteristics and deviation from linear group delay. Good out-of-band sidelobe suppression of -27 dB and group-delay ripple of ?9.5 ps is achieved for fully apodized grating devices.

Photosensitivity in optical fiber and silica-on-substrate waveguides

Ultraviolet light irradiation of optical fibers or silica-on-silica channel optical waveguides photoinduces a permanent refractive index change in the core of the optical waveguide. The effect called `photosensitivity provides a versatile photolithographic means for processing glass in the form of optical fiber or planar optical waveguides in order to fabricate optical waveguide devices that have applications in optical fiber communications and optical sensor systems. This paper reports on some recent experimental results on photosensitivity in optical fibers and planar optical waveguides and its use in the fabrication of optical waveguide devices.

Influence of fringeless UV post-exposure on index modulation amplitude in fiber Bragg gratings

Dynamics of the refractive index modulation amplitude during uniform UV post-exposure of fiber Bragg gratings at 248 nm are examined. The change in index modulation amplitude depends on the strength of the grating prior to the post-exposure and also on the degree of zero-order suppression in the phase mask used to write the grating. Furthermore, during the post-exposure, diffraction orders are observed emanating from the fiber in the absence of a phase mask. This observation is incorporated into the development of a model that successfully explains the post-exposure dynamics.

High-g accelerometer based on in-fiber Bragg grating: a novel detection scheme

A simple accelerometer detection technique based on the measurement of the optical convolution between two identical fiber Bragg gratings, one used as a reference and the other used as a sensor, is presented. Theoretical calculations on sensitivity and for different tolerances on linearity are considered for uniform and apodized gratings at different reflectivity levels. Experimental measurements made with a Hopkinson bar setup where one grating is used as an acceleration sensor are presented.

Ion-exchanged Mach–Zehnder interferometers in glass

Ion-exchanged Mach-Zehnder interferometers are produced in glass. The effect of fabrication parameters on their optical response in relation to their constituent components is investigated.

Modification of the properties of silica glasses by ion implantation

High energy MeV ion implantation of fused silica and Ge- doped silica renders these materials photosensitive. The physical processes involved are closely related to the photosensitization of Ge-doped silica by UV irradiation but present certain characteristics that are different. We discuss the results of studied of the induced absorption and refractive index changes under different preparation conditions, annealing sequences and subsequent bleaching by ArF and KrF excimer radiation. We include the results of a study using positron annihilation spectroscopy of the defects introduced by ion implantation and subsequent annealing and bleaching.

Fabrication and characterization of ion-exchanged glass channel waveguides with etched and diffused grating taps

Submicron etched and diffused gratings are produced on ionexchanged glass waveguides. Efficient interaction between the guided light and the grating is observed. Propagation properties of these components are thoroughly investigated.

Fabrication and characterization of submicron gratings written in planar silica glass with a Focused Ion Beam.

Groove patterns with submicron lateral sizes and depths of several hundreds of nanometers have been defined in silica glass surfaces by focused ion beam implantation and differential wet etching in hydrofluoric acid solutions. Nonperiodic arbitrary patterns can be defined and variable depth achieved through local ion dose control. The fabrication of diffractive optical elements for excimer lasers in the ultraviolet is described.

Optical damage threshold of ion-exchanged glass waveguides at 1.06 um

We report the measurement of the damage threshold of optical waveguides made by ion exchange in glass subjected to high peak power pulses from a mode-locked/Q-switched YAG laser operating at a wavelength of 1.06 mm. We found that waveguides made from a potassium-sodium exchange could tolerate at least ten times more guided peak power than silver-sodium exchanged guides.

Integrated optical Mach-Zehnder interferometers in glass

A potassium ion-exchange process is employed to make integrated optical Mach-Zehnder interferometers in a glass substrate. An extensive study is carried out to determine the contribution of different components of the interferometer in its performance. Propagation properties of Mach-Zehnder interferometers, straight and S-shape waveguides, and Y-junctions are investigated.