ABSTRACT
In this chapter we analyze the optical detection techniques, while techniques generating an electronic detection signal are reviewed in Chapter 10.
Optical detection systems can be divided into free optics and integrated optical systems. Free optical techniques use free propagation optics to test the optical response of the target inside a detection chamber of the lab on chip. In this case, a transparent window is generally created on the surface of the lab on chip and it is inserted into an external device integrating one or more optical sources, generally lasers, and one or more optical detectors. The sources illuminate the sample inside the lab on chip and the detectors collect the output light and analyze it to provide the detection result. In the case of integrated optical detection, an integrated optics circuit is realized inside the lab on chip. Sources and detectors can be either integrated onto the lab on chip too, using either monolithic or hybrid technologies (see Section 6.3.1), or placed in an external equipment where the lab on chip has to be inserted. In both cases, sources and detectors have to be coupled with the integrated optical circuits and, if the external solution is chosen, the chip has also to integrate an optical interface between the on-chip waveguides and the external system (see Section 6.5.4).
