Abstract: A chemical sensor based on an indicator dye wherein a light transmissive element containing the indicator dye is made of a hygroscopic polymer. The polymer may be, for example, a polyimide or PMMA or other polymer. In an alternative embodiment the light transmissive element is doped with metal nanocolloidal particles. One embodiment may include a reference photodiode and differential amplifier to compensate for the fluctuations of the intensity of the light source. The light source may be pulse modulated. The sensor may include calibration means comprising a reference sample of the chemical to be detected and a precision delivery means. A method of fabricating the polymer and metal nanocolloid is disclosed wherein the nanocolloid is produced by generating a pulsed laser plasma in a suspension of metal particles and an organic solvent and adding the resulting solvent colloid to a solution containing the polymer.