Absorbance-Based Integrated Optical Sensors

Optochemical sensors have had a huge expansion and in recent years interesting sorts of optical sensor have been developed which make use of the integrated circuit microelectronic technology and the optical technological advances achieved in the telecommunications industry. These devices are based on optical fibers, planar waveguides or the combination of both supports as light-guiding structures and offer an enhanced performance thanks to a miniaturized size, a feasible mass production at low cost, the possibility to measure at large distances and the capability of reaching places hard to access for the in situ monitoring of environmental or medical parameters. In this chapter, we provide an overall view of integrated chemical sensors based on absorbance measurements, describing their main characteristics, advantages and drawbacks. In order to focus on these types of devices, first of all, a brief classification is given, in terms of the interaction mechanisms and the reactive phases or membranes that are involved in the response, and the radiation transmission medium. Next, different waveguide configurations are briefly described because of to the relevancy of these structures as the main constituent of integrated optodes and, finally, some absorbance-based integrated sensors are detailed.