5 Biomedical Optics and Lasers B. Cem Sener Department of Oral and Maxillofacial Surgery Faculty of Dentistry, Marmara University, Istanbul, Turkey 1. Introduction Electromagnetic energy is the source of life in our universe. Living organisms require energy to survive. Basic organisms provide this energy externally as a raw material (basic molecules like sugar) and convert it to energy (digestion of food). However some organisms, like green plants, can directly absorb radiation energy and store after a chemical conversion. Excessive energy is stored with a chemical reaction as adenine triphosphate (ATP) synthesis. Complex organisms digest more simple ones that contain readily synthetized ATP in an understanding of a food-chain. Under specific conditions complex organisms, partly, can absorb radiation energy and use it directly or store with ATP. Therefore, different bands located in certain parts of wide radiation energy spectrum can be used directly or indirectly to maintain our life. With this respect; interactions with radiation is mainly subjected within this context either with positive and negative ways, however both paths can be a matter of survival. In that broad spectrum of radiation energy only a small part is visible (between 400 to 700 nm wavelength) for human beings (light). (Figure 1) However, mankind has converted or digitalized rest of spectrum to monitor and understand how it works for many purposes, like industry, navigation, communication, industry, research, military and medicine. Focus of this chapter is centered on a specific form of radiation, L.A.S.E.R. Amplified light generated by stimulated of emission can be defined as purified and well-disciplined form of radiation and therefore has a special importance in biomedical applications with its advanced features. Moreover; developments in optics, computer hardware and software, electronics and nanotechnology have widen the scope of LASER radiation in biomedical applications. This chapter aims to give a basic understanding of laser and its place as a solution for several issues struggled in clinical and laboratory environments of biomedical sciences. Innovative techniques centered on laser application are also given besides emphasized basic technical knowledge so that readers can develop their informative wallet to build up a vision for further steps both in bio- and engineering sciences. This would also have a collateral effect to prepare current reader as developers, researchers or users for the future. 2. History Interaction of radiation energy with biologic systems is not a new concept and has been focus of human beings for millenniums. Evidences in ancient Greek writings for use of sun www.intechopen.com