New design for optical porous silicon gas sensor

LEANDRO N. ACQUAROLI; RAÚL URTEAGA; R.R. KOROPECKI

Valencia

Conferencia; 7 Internatonal conference PSST 2010; 2010

A simple system for the detection of external analytes (EA) to the atmosphere employing a freestanding nanostructured porous silicon optical microcavity was design and built. The system is based on the measurement of the transmittance changes as a function of the incidence angle of a monochromatic laser beam. Using a matrix formalism and effective medium theories we calculate the optimal conditions for the system so as to obtain the best sensitivity of the sensor. In this work we test the system with isopropyl alcohol vapor diluted in a N2 stream. The time response of the detector is very fast (lower than 1second) and the active area is small (about 100μm2). With the system proposed we were able to detect changes in the concentration of the EA as small as 1 ppm, which is equivalent to a change in the refractive index of 10-6. Below this value, variations in temperature become significant and must be taken into account to obtain reliable measurements.