Tech Questions? Get the Answers: 5/10/2023

Q: What is a laser?

A: Imagine a birthday party with a large group of ten-year-olds who have been eating candy since they showed up, and they are all in a hallway with one closed end. The kid at the far end of the hallway jumps up and sees that the cake has been brought out. Once that kid starts running for the open end of the hallway saying there is cake, the rest of those ten-year-olds start running with him directly for the cake without spreading out. That is a very rough analogy of how a laser works; the candy is the energy into the laser exciting the electrons of the laser material, the hallway is the laser cavity, the closed door at the end is a mirror, and the open end of the hallway is the output coupler.

When enough electrons get excited that there are more excited than in the ground state, that is called a population inversion. Since electrons don't want to stay in the excited state, they want to fall back to their ground state. When electrons fall back to the ground state, they have to release the energy that caused them to get excited. In many cases, this energy is released as photons or particles of light. When a photon travels past other excited electrons, it can knock them down to the ground state releasing their photons as well, but in the same direction and in step, or in phase with the first photon. This causes an avalanche of photons all headed in the same direction like the children sprinting out of the hallways toward the cake.

The word laser is an acronym that stands for Light Amplification by Stimulated Emission Radiation. But don't let the word radiation scare you, it is just something that radiates like a radio station or light bulb, but there are some distinct differences including it is non-divergent and stays in a straight line, and is monochromatic or only one color. In short, a laser turns electrical energy into directed coherent light energy.

Lasers are used in many industries from medical to entertainment, from research to restoration. Sampling the air in the upper atmosphere and in mines, reading bar codes, and even nuclear fusion, lasers are an effective way of directing energy to a precise spot. If you have questions about lasers contact your local tech specialist.

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