DEVELOPMENT OF A PROTOTYPE GAS SENSOR USING SURFACE-PLASMON RESONANCEON GRATINGS

A good basis has been established for the development of a prototype g as sensor using the phenomenon of surface plasmon resonance. By exciti ng a surface plasmon on a metallic diffraction grating that is twisted azimuthally so its grooves are not perpendicular to the plane of inci dence, and with suitable choice of input and output polarization, a re sonance maximum is detected (as opposed to the usual resonance minimum ). The operation of the sensor is based on the measurement of this res onance maximum on a background of weak signal and incorporates a sensi ng head made remote from both the source and detector by means of fibr e optics. Its use is demonstrated by sensing remotely the condensation of almost-equal-to 0.9 nm of isopropyl alcohol onto a silver-coated g rating surface.