The aim of this work is to measure the temperature variations by analyzing the plasmon signature on a metallic surface that is periodically structured and immersed in a liquid. A change in the temperature of the sample surface induces a modification of the local refractive index leading to a shift of the surface plasmon resonance (SPR) frequency due to the strong interaction between the evanescent electric field and the metallic surface. The experimental set-up used in this study to detect the refractive index changes is based on a metallic grating permitting a direct excitation of a plasmon wave, leading to a high sensibility, high-temperature range and contactless sensor within a very compact and simple device. The experimental set-up demonstrated that SPR could be used as a non-invasive, high-resolution temperature measurement method for metallic surfaces.

In this paper we propose contact lens central thickness measurement with a low coherence interferometry technique using either a SLED source or a broadband continuum generated in air-silica Microstructured Optical Fiber (MOF) pumped with a picosecond microchip laser. Each of these sources associated with the interferometer provides, at the same time, good measurement resolution and quick signal recording without moving any optical elements and without need of a Fourier Transform operation. Signal improvement is performed afterwards by a numerical treatment for optimal correlation peaks detection leading to central thickness value of several contact lenses.

A deep metal grating enables quasi-phase-matched simultaneous excitation of two counterpropagating surface plasmon modes by means of its +1st and –2nd diffraction orders. The resulting angular reflection spectra of the scattered –1st and zeroth orders exhibit three interleaved zeros and maxima in a range centered around the Littrow angle. The spectra differ thoroughly from the usual reflection dip resulting from single-order plasmon coupling that produces strong absorption. The zeroth and –1st orders exhibit two crossing angles enabling high-sensitivity common-mode detection schemes designed to reject variations in source power and environmental noise. The proof of concept and experimental assessment of this new surface plasmon resonance (SPR) sensing scheme are demonstrated by monitoring gases in a pressure-controlled chamber. A limit of detection (LOD) of 2 × 10⁻⁷ refractive index unit (RIU) was achieved.

The detection of refractive corneal surgery by LASIK, during the storage of corneas in Eye Banks will become a challenge when the numerous operated patients will arrive at the age of cornea donation. The subtle changes of corneal structure and refraction are highly suspected to negatively influence clinical results in recipients of such corneas. In order to detect LASIK cornea interfaces we developed a low coherence interferometry technique using a broadband continuum source. Real time signal recording, without moving any optical elements and without need of a Fourier Transform operation, combined with good measurement resolution is the main asset of this interferometer. The associated numerical processing is based on a method initially used in astronomy and offers an optimal correlation signal without the necessity to image the whole cornea that is time consuming. The detection of corneal interfaces - both outer and inner surface and the buried interface corresponding to the surgical wound – is then achieved directly by the innovative combination of interferometry and this original numerical process.

An optical plasmonic hydrogen sensor is proposed, based on what we believe to be a novel configuration named plasmon-triggered switching. This configuration, involving two propagative orders diffracted by a deep metallic grating combined to a hydrogen-sensitive layer, is capable of measuring hydrogen concentrations. The two diffracted orders enable a differential measurement, which estimates a change of refractive index through evolution of the relative diffraction efficiency of each order at fixed wavelength and fixed angle, while cancelling any drift of the input laser source and other disturbances and allowing both a high sensitivity and a very low limit of detection (LOD). Experimental results, using a simple implementation involving one laser and two detectors, demonstrate a LOD without any signal post-processing, below 0.2 ppm (2.10⁻⁵% Vol) in filtered air, are in good agreement with simulations and exhibit very good repeatability. The proposed setup represents a very promising, compact and cost-efficient approach to real-time hydrogen sensing using a thin H₂ sensitive and selective palladium thin layer deposited on a gold grating for highly sensitive plasmon coupling.