After a brief introduction to some commonly used coherent and incoherent sources, and some stabilisation techniques, a variety of detectors commonly used in sensor applications are described. Emphasis is then given to scattering techniques and the most commonly used spectroscopies, which very often may simultaneously incorporate a variety of applications based on the interaction of light with matter, including the latest advances in THz measurement and instrumentation systems, are described. Finally, an introduction to optical fibre sensing is provided.

The design, manufacture, properties and application of amorphous semiconductors as image sensors, are described. After introducing the relevant concepts and background theories, the preparation, structure, properties and performance of two important classes of amorphous semiconductors are be described in some detail. These are amorphous selenium based (a-Se) and hydrogenated amorphous silicon (a-Si:H) photoreceptors. X-ray imaging techniques and application of amorphous semiconductors as X-ray image sensors are discussed. Recent advances in optical application of amorphous semiconductors are briefly explained.

Conducting polymers have a wide variety of applications in gas and volatile chemical sensing. Because the chemistry is readily amenable to attachment of substituent groups on to the polymer backbones, it is possible to create tailored adsorbent materials that are capable of high sensitivity to a large number of chemicals. A brief description of these possibilities is given. Much research is focused on the development of sensor arrays that mimic the functioning of the human nose, and with conducting polymers, the inherently high sensitivity to polar compounds allows correlation of sensor response to human response in certain situations. The evolution of this technology will open up a new frontier of objective odour measurements that is a radical change from the traditional chemical analytical methods.