Measuring optical signals in the femtowatt (10-15) to nanowatt (10-9) range can be a daunting task. In order to achieve significant improvements in noise rejection we need to turn to a lock-in amplifier, which can improve noise rejection by 3 orders of magnitude or more.

Fluorescence spectroscopy has been used to characterise natural organic matter (NOM) in water. Excitation-Emission maps reveal the nature and concentration of NOM in river water and can be used as a routine analysis technique in water treatment facilities.

The ultimate instrumentation for trace gas analysis and detection in air quality monitoring as well as industrial process control would be one that can simultaneously provide a sensitive, selective, and fast, multi-gas measurement with wide dynamic range all in a compact and robust system. One of the few such promising technologies that can deliver these requirements is laser based photoacoustic spectroscopy (PAS).