An Intro to Lasers

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Storyboard Description

This lesson is a precursor to a lesson on the components of a laser beam welding machine. To properly understand how these components work, it's important to know the fundamentals of laser beam creation.

Storyboard Text

  • Before we begin discussing the components of a laser beam welding machine, it's important to know what laser light is and how it's created.
  • Lasers are a special, man-made form of light. While natural light and light from light bulbs are made up of several different wavelengths moving in different patterns, laser light is comprised of exactly one wavelength moving in the same pattern.
  • Please read the content on the dry-erase board and easel to learn a bit about what laser light is.
  • A wavelength is measured from crest to crest and each wavelength produces a different color. Since the wavelengths in the light from the sun differ, many different colors are produced. Laser light, however, produces only one.
  • So, we now know a bit more about what laser light is, but how is it created? Well, it all comes down to electrons. The electrons in an atom are always moving and they are easily agitated. Even the electrons in something as solid as stone are in constant motion. When an atom receives energy in the form of light, heat, or electricity, it absorbs it, giving its electrons the energy to move from a lower energy orbit to a higher energy orbit. 
  • Eventually, however, through a phenomenon known as spontaneous emission, the electrons want to return to their ground state and when they do, they release their extra energy as a photon. A photon is a particle of light.
  • Whether or not you realize it, you witness atoms emitting photons all day. When the coil on your stovetop burner glows red, you’re witnessing electrons, excited by heat, emitting red photons. In reality, anything that produces light, including the screen you’re currently looking at, releases photons.
  • Now, to make a laser beam, all you need to do is excite a group of atoms to the point that they will emit light. This is done by infusing the atoms with energy through the use of heat or electricity. Once an electron is heated or excited to a higher energy orbit and drops back down to its ground state, it will emit a photon. As it does so, it stimulates others to do so as well, until you have an illuminating cascade of light.
  • Now, instead of allowing all of this light energy to scatter and dissipate into the air, we can put it to good use by trapping the light between two mirrors and let it bounce back and forth on the mirrors’ reflective surface. As this occurs, the light passes through the rest of the atoms that are also trapped between the mirrors. As the photon passes by these atoms, it coerces excited electrons of the same energy level to drop to their ground state and emit photons as well, giving us several identical photons. This phenomenon is known as stimulated emission.
  • The great thing about photons is that they are very eager to follow suit with other photons. Because of this quality, they emit in the same phase, direction, and wavelength as one another, all qualities needed to form laser light. Now, if we were to create a small opening in one of our mirrors, we would release these photons from their ricocheting in the form of a single beam of coherent light: a laser beam. 
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