Main Article Content
The new sources of light (laser and led) that have been invented and developed during the last fifty-sixty years have given origin to a true scientific and technological revolution. This article synthetically follows the main steps of the history of light, which started by studying the properties of solar emission, and introducing the concept of electromagnetic wave. At the end of the 19th century there was experimental evidence that it was necessary to complicate the approach by introducing the assumption that the electromagnetic energy is a discrete, and not continuous, quantity. The new concept led to design and realization of the laser and the led. Through the utilization of these sources fundamental progress was achieved in both science and technology, by deepening the description of wave-particle dualism and of the coherence concept, by putting on a completely new basis information and communication technology, and by giving new tools to industrial and biomedical sensing.