How a Laser Works

The definition of a laser can be understood by expanding the acroynm -- "Light Amplification by Stimulated Emission of Radiation" -- and then expanding each word in the acronym.

Light

Light is a small window of frequencies of electromagnetic radiation (EM) that can be sensed by the eye of various organisms. The smallest unit of EM (which includes light) is called a photon.

Electromagnetic radiation is a photon wave in space or through matter. EM radiation has an electric and magnetic field component that oscillate in identical waves. One wave consists of a trough and a crest. The distance between two adjacent crests or troughs is called the wavelength.

Wavelengths are measured in hertz. One hertz is equal to one oscillation per second. Wavelengths vary in size from the very short gamma rays smaller than atom nuclei to the long radio waves the size of buildings. The shorter the wavelength, the higher the hertz designation.

This hertz designation is called frequency. So, gamma rays are considered to have a very high frequency. As waves cross boundaries between different media (such as air to water), their speeds change but their frequencies remain constant.

Amplification

In a laser, light of a specific wavelength passes many times back and forth through something called "gain medium." A gain medium can be something such as certain crystals, gases or semiconductors The light is amplified (increases in power) as it bounces repeatedly between two mirrors. One of the two mirrors is partially transparent. Part of the light that is between the mirrors passes through the partially transparent mirror and escapes as a beam of laser light.

Stimulated

"Stimulated" means "excited to activity or growth or to greater activity." For example, when the heating element in a toaster turns bright red, the red color is caused by atoms that were stimulated by the heat in the electricity to release red photons.

Emission

"Emission" means "put into circulation." For example, in the toaster example above, the red photons were put into circulation; they were emitted.

Radiation

"Radiation" means "the process of emitting radiant energy in the form of waves or particles." Here we are back to the emitting of light waves as discussed under "Light" at the top of this discussion.

Where Are Lasers Used?

The most common single application of lasers is in optical storage devices such as compact disc and DVD players. Another use is surface engraving or the engraving within crystal glass.

Something a bit more fascinating is the engraving of photos onto materials such as granite or marble. To begin this process, the data from a digital photo is entered into a computer. The computer drives a laser that will scan over a photo medium such as a slab of marble or granite.

When engraved with lasers, microscopic chips are etched away from the surface, resulting in a frosted appearance. In the gift idea below, you can see how the chips were etched away.

Each of the tiniest areas in a digital photo is called a pixel. Each pixel or small group of pixels determines what data will be driving a laser head during one tiny point of time. The place where the laser beam touches the surface of the photo medium is called the focal point.

This point is much smaller than the diameter of a human hair. The area inside this focal point is reaches a temperature greater than the surface of the sun and vaporizes the photo medium at that point only. A cooling system is in effect to prevent other areas from retaining heat.

The laser engraves areas that has "data". So, if there is any black areas, the laser will skip over that area. For instance, where people in the photo have black hair, that area will remain the color of the polished marble. The lighter areas (which is the data) will be engraved.

For more information on having your photo engraved onto a granite or marble plaque or even onto an aluminum dog tag, see the Granite & Marble section of this website.

You e-mail a digital photo (like the picture below.) We will laser etch it onto granite, marble or even an aluminum dog tag.

As it says at the top of this article, light is an electro-magnetic wave and therefore has an electric field. A laser beam creates an electric field greater than 10 million volts per centimeter.

The laser beam creates free or unattached electrons at its focal point within the crystal. The free electrons, accelerated by the electric field created by the laser beam, cause the high energy electrons to collide with atoms and ions in the area of focus.

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