History and Fundamentals of Lasers and Light Sources in Photomedicine

Abstract

The race to create the laser is full of intrigue, and several books have addressed the topic. In short, Charles Townes created the MASER (microwave amplification by stimulated emission of radiation), which was a nonvisible light predecessor for the LASER (light amplification by stimulated emission of radiation). Townes and Arthur Schawlow at Bell Labs published their ideas in a scientific journal (Schawlow 1965) about the same time that Gordon Gould (who had coined the term “laser”) filed a patent application (Hecht 1992). There is still debate about the real inventor of the laser. Townes and Schawlow, along with Soviet pioneers, received the Nobel Prize for their work with masers and lasers. Gould, after many legal struggles, was recognized for his four patents in 1988. Theodore Maiman was the eventual winner of the great laser race (at least in terms of building the first working device) when, on May 16, 1960, despite being discouraged by his employer (Hughes Labs), he was able to put mirrors at the end of a ruby rod and create the first working laser. The rod was surrounded by a helical flash lamp (Figure 2.1). Javan later produced the first gas laser (Helium neon). In 1962, the first semiconductor laser was created. Q-switched lasers were first introduced in 1962 and mode-locking lasers in 1964 (vide infra).