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In this study, a novel gas sensor based on evanescent field coupling between single mode side polished fiber and solvatochromic dye dispersed polymer waveguide was demonstrated. We fabricated a side polished optical fiber device as a volatile organic compounds gas detector. Solvatochromic dye was coated on the top of the side polished optical fiber to take advantage of evanescent field coupling. The solvatochromism can be defined as the phenomenon whereby a compound changes color, either by a change in the absorption or emission spectra of molecule, when reacted in different VOCs. The device reacted to polarity gases like a hexane, butane, xylene etc. The resonance wavelength was shifted by the xylene concentration which range was 0.1 ppm ~ 100 ppm. Also, the response with the concentration was lineer and the detection limit was 0.1 ppb.

and were added in the concentration of 1 - 3 wt.% to improve long-term stability for the thick film gas sensor. Short-term sensor resistances up to 90 h were measured to investigate the stabilization time of initial resistance in air. Long-term resistance drifts in air and in gas to 5000 ppm methane for the sensors annealed at for 1 h and continuously heated at an operating temperature of were also measured up to 90 days at an interval of 1 day. The long-term drifts in methane sensitivity for the three metal oxide-doped sensors are closely related to methane sensitivity level, catalytic activity, and long-term drift in sensor resistance in air. Those stabilities are mainly discussed in terms of oxidation state and catalytic activity.