For the Technically Minded – A Bit More Detail about Lasers
Cutting lasers deliver high energy concentrations because they generate coherent light.
Coherence means the energy is delivered in a narrow band of wavelengths – similar to the way an FM radio station broadcasts at a specific wavelength, rather than spreading its energy across the dial. This is very different from white light (like sunlight) which contains a broad spectrum of wavelengths. This is demonstrated every time we see a rainbow; raindrops act like tiny prisms and spread out the sunlight into its component wavelengths, which our eyes perceive as colors.
The great advantage of coherence lies in the way materials respond to lasers of different wavelengths. When visible light is absorbed by a material (as opposed to being reflected), the material heats up – think of the way an asphalt road warms up under sunlight. The light is agitating the atoms that make up the material; their vibration is what we perceive as heat. Cutting lasers deliver light that isn’t just all one color – it’s all one shade of color. Another way of putting this is that almost all the energy of the laser is delivered at one specific wavelength. Different materials heat up to a different extent when hit by lasers of different wavelengths. This is what allows medical and dental lasers to be “tuned” to particular tissues. They will heat only those tissues while leaving other kinds unaffected.
Hard tissue lasers have a wavelength that is highly absorbed by the calcium and other hard materials in teeth. Soft tissue lasers, on the other hand, are tuned to wavelengths that are readily absorbed by watery materials. (Gums and the mucosal lining of the mouth contain lots of water!)