How Do Lasers Work?

Lasers have revolutionized the way that many devices and machinery work. From CD players to machines that cut metal, lasers play an important part in many daily activities, right under the noses of unaware consumers. Lasers are used in dental drills, tattoo removal, hair replacement, eye surgery, and there is now even a method of using laser beams to create rain. While some lasers are harmless, others are extremely dangerous and not all lasers are the same. However, all lasers work in pretty much the same way. This article will strive to explain how lasers work and what they do.

What Do Lasers Do
Lasers work in much the same way as light bulbs do, but instead of dispersing the light, lasers focus it. Laser stands for Light Amplification by Stimulated Emission of Radiation. Lasers use electricity from a battery to excite a large number of atoms at once. These atoms will then have electrons in identical positions that will release the exact same wavelength of color at the same time. This is the underlying principle of all lasers.

States of Excitation
All atoms are constantly moving due to electrons orbiting around the nucleus of each atom. This movement and placement of the electrons is actually what makes up individual objects. It is also what makes up how much energy an atom has. An electron's original placement around the nucleus is called the "ground-state energy level". As electrons move further away from the nucleus in an atom, they gain more potential energy. This is referred to as an "excited level". The electron can only hold this position for a fraction of a second and when it comes back to its original placement, the extra energy is released as photons.

Photons
Photons are particles of electromagnetic radiation that have no mass. Some photons are "light photons", which are particles of light. A laser uses light photons to create a targeted beam of light but photons are seen all the time. Anything that emits light does so by exciting atoms and causing the electrons to change their orbit around the nucleus, releasing photons. For example, televisions work by using electricity to excite phosphorous atoms to varying degrees so that different wavelengths of colors are emitted. Likewise, when a tungsten filament in a light bulb is excited by electricity, light photons are again released.

Laser Light
Laser light is different from normal light. Whereas the light from a light bulb or flashlight is random and spread out in many directions, laser light is organized and follows a narrow beam. This is because a laser stimulates all the electrons at once and does so with a specific amount of electricity. By doing this, the laser makes sure that all of the electrons are moved to the same orbital path around the nuclei of their respective atoms. When the electrons lose their energy and return to the ground-state energy level, they all release their photons at the same exact time.

Ruby Lasers
A ruby laser, the kind that produces red light, is slightly different from other types of lasers. Ruby lasers consist of a flash tube, a ruby rod (or some other red, partially transparent object), a mirror on one side, and another mirror on the other side that is partially covered in silver. The flash tube uses electricity to create light like a normal light bulb and intermittently pulses to excite atoms in the ruby rod. As the atoms fly around, they bounce back and forth off of the mirrors and excite other electrons. Eventually, all of the atoms leave the silver-coated piece of mirror in a narrow beam.