Fiber optic Surface Plasmon Resonance sensor based on wavelength modulation for hydrogen sensing.

A new design of a fiber optic Surface Plasmon Resonance (SPR) sensor using Palladium as a sensitive layer for hydrogen detection is presented. In this approach, a transducer layer is deposited on the outside of a multimode fiber, after removing the optical cladding. The transducer layer is a multilayer stack made of a Silver, a Silica and a Palladium layer. The spectral modulation of the light transmitted by the fiber allows to detect the presence of hydrogen in the environment. The sensor is only sensitive to the Transverse Magnetic polarized light and the Traverse Electric polarized light can be used therefore as a reference signal. A more reliable response is expected for the fiber SPR hydrogen sensor based on spectral modulation instead of on intensity modulation. The multilayer thickness defines the sensor performance. The silica thickness tunes the resonant wavelength, whereas the Silver and Palladium thickness determine the sensor sensitivity. In an optimal configuration (NA = 0.22, 100 µm core radius and transducer length = 1 cm), the resonant wavelength is shifted over 17.6 nm at a concentration of 4% Hydrogen in Argon for the case of the 35 nm Silver/ 100 nm Silica/ 3 nm palladium multilayer.

Waveguide sidewall roughness measurement on full wafers by SEM-based stereoscopy.

We present a technique aiming at sidewall roughness measurement on integrated optical silica waveguides using a scanning electron microscope. The technique uses the principles of stereoscopy to retrieve sidewall topography. Practical implementation details and first results are provided.

Angular displacement fiber-optic sensor: theoretical and experimental study.

An optical-fiber sensor based on twist-induced optical activity has been developed for measuring angular displacements at low temperature. The sensing part is composed of a fiber coil rotated between two points, which induces a twist of two sections of fiber. A theoretical study of the evolution of a general input state of polarization in the sensor gave us its main characteristics. Then experimental investigations permitted the construction of a sensor to take angular measurements over a 100-deg range with an accuracy of 0.2 deg. The thermal sensitivity of this kind of sensor is also briefly reported.

Thermoplastic film camera for holographic recording of extended objects in industrial applications.

Optimization of a thermoplastic film recording camera and its performance for holography of extended objects are reported. Special corona geometry and accurate control of development heat by constant current heating and high-resolution measurement of the development temperature enable easy recording of reproducible, large aperture holograms. Experimental results for transfer characteristics, diffraction efficiency characteristics, and spatial frequency response are given.