Table 13.1 summarizes the mechanisms of lasers and light-based systems. The central dogma to these therapies is predicated on the theory of selective photothermolysis (SP), where in theory any target can be selectively destroyed if an optimal thermal relaxation time of the target is matched with the optimal chromophore. Biologically, the active chromophores are melanin, hemoglobin, and water. As devices have matured, it has become increasingly evident that there are other mechanisms besides SP. These include refinements of SP such as fractional photothermolysis, photopneumatic therapy, and photodynamic therapy.
When SP was first introduced, single wavelength lasers were the only modality of accomplishing these clinical effects. More recently, broadband light sources (often referred to as pulsed light) which use a flashlamp with selective filters can replicate and often surpass clinical results that are only attainable with single wavelength lasers. With the development of sophisticated cooling systems to protect the epidermis, the use of selective filters and photon recycling, pulsed light systems can replicate and often surpass many laser applications.