In 1917 Albert Einstein put forward a theory of “stimulated
emission” - that photons could “stimulate” the emission of
another photon that would possess identical properties to the first1.
This is the idea behind laser light and in 1958 Townes and
Schawlow2 worked on this theory to establish the principle that led
to the development of the Laser: Light Amplification
by Stimulated Emission of Radiation. In 1960 Theodore Maiman
demonstrated the first practical laser with a crystal of ruby
stimulated by a flashlamp and mirrors to amplify the lasing
action3. The beam was a deep red colour with a wavelength of 694
nm. Since that first laser, many more materials have been
discovered that are capable of producing laser light including
dyes, gas mixtures and semiconductor materials, many of which
are described below and presented in table 1.
It has taken decades to develop reliable, appropriately designed
laser systems for routine use in medical and other applications4.
More recently, Intense Pulsed Light (IPL) systems are being used
for many similar applications as lasers5