Lasers: A Gift from Quantum Physics
Lasers are everywhere. Want to remove unwanted hair? Try laser hair removal. Tired of wearing glasses? Laser vision correction procedures are available. Laser therapy is even used to remove unwanted body fat. (This doesn't sound like such a bad idea post-Thanksgiving...)
Have you ever gone to a laser light show? Laser light shows use colored laser beams to project beautiful images synchronized to music. Look around town, and you’ll notice colorful Christmas decorations that are now done with laser light projectors.
It is hard to believe that the laser was invented only in 1960. Many people don’t realize that the term "laser" originated as an acronym for "light amplification by stimulated emission of radiation." The acronym is now so common it’s no longer written in capital letters.
So what’s the science behind lasers? And how do they really work?
The laser is one of the most unique and useful technologies of modern times and is a gift of quantum mechanics. Developed in 20th century, quantum mechanics studies the smallest scales of energy of atoms and subatomic particles. Quantum theory states that electrons in an atom have different energy states, and the lowest energy state is called ground state.
When electrons are in an excited higher energy state, their time there is very short. Almost immediately, they jump to their normal or “ground” state, giving off photons, tiny particles of light. This process is generally random and is called spontaneous emission, but it doesn’t produce a laser. Instead, this process gives us the light in an ordinary neon light bulb.
Lasers depend on the coherent emission of light by many atoms, all at the same frequency. In a laser, an atom undergoes a transition and emits a photon in the presence of many other photons that have equal energies. A process known as stimulated emission causes the light emitted by this atom to propagate in the same direction and with the same phase as surrounding light waves.