Lasers have found their way into a huge array of uses that few would have imagined when they were first developed. They are utilized in everything from industrial processes to weapons to medicine to consumer electronics, and new uses keep coming along. As an example, newer upscale car models are being equipped with laser headlights and taillights. To get a handle on how versatile lasers are, it helps to learn a bit about how they work.
Starting With the Basics
The word laser actually stands for light amplification through stimulated emissions of radiation. This sounds rather abstract, so let’s start with a concrete example of how a laser goes about amplifying light. All around, there are materials of easily defined colors. The colors are produced when light hits them and they absorb this energy. In turn, they release this energy in a narrow bandwidth that’s perceived as blue, red, or whatever. With a laser, energy in the form of electricity or light that can include radio waves up to x-rays is “pumped” into a container holding a solid, liquid, or gas. Energy can also be provided through chemical reactions within the laser itself. Like with the previous example, this material takes the energy and re-emits it as a single frequency. Having only one frequency allows it to be applied more effectively for a particular task. For example, visible light passes through glass while infrared light is blocked, but infrared light is absorbed as heat more effectively by materials like steel. This is why infrared laser are often used to cut steel.
Setting Things Straight
Having a single frequency also permits the laser to perform its next operation of lining up these rays of light in a single direction so that all this energy is concentrated in a very narrow beam. To perform this operation, a pair of mirrors are placed at either end of a laser device. One of these mirrors is semi-transparent so that light of a specific frequency moving in a specific direction can pass through while light hitting this mirror at any other angle is reflected back. When light photons successfully exit through this mirror in alignment with one another, it’s referred to as coherence.
Kinds of Lasers
Of all the types of laser out there, the one most often encountered by most people is the semiconductor laser. This kind uses an LED, light-emitting diode, to produce light when an electrical current passes through it. Capped on both ends with mirrors, it provides a cheap, low-powered beam that can be very tiny that’s used to read and write CDs and DVDs, detect smoke and carbon monoxide in the home, transmit signals from remote controls, operate in laser printers, carry information through fiber optics, and even power simple laser pointers. In medicine, the most common type of laser uses carbon dioxide to create an infrared beam that cut into skin while simultaneously cauterizing it. This type of laser is also highly effective in removing cataracts, pulverizing kidney stones, and vaporizing decayed tooth material. In industrial processes, lasers relying on either carbon dioxide or helium-neon gas generate infrared beams for cutting, welding, and more recently, fusing materials together in 3D printing. Energy for these types of lasers is supplied by passing an electric current through the gas.