In 1916 Albert Einstein wrote to a friend "A splendid light has dawned on me about the absorption and emission of radiation." Einstein never created a laser, but at that time he theorized the concept of stimulated emission, which is the scientific basis for the creation of laser light. The first ruby laser was developed in 1960 and many other lasers were created rapidly thereafter. Dental researchers began investigating lasers' potential and Stern and Sognnaes reported in 1965 that a ruby laser could vaporize enamel.3 The thermal effects of continuous wave lasers at that time would damage the pulp.4 Other wavelengths were studied over the ensuing decades for both hard and soft tissue applications.
Practitioners and researchers began to find clinical oral soft tissue uses of medical CO2 and Nd:YAG lasers until in 1990 when the first pulsed Nd:YAG laser designed specifically for the dental market was released. The year 1997 saw the FDA clearance of the first true dental hard tissue Er:YAG laser and the Er,Cr:YSGG a year later. Semiconductor based diode lasers emerged in the late 1990s as well. Recently a CO2 laser was approved for use on tooth structure.