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How do laser pointers work?

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📓 The short answer

Laser pointers work by exciting atoms so their electrons release light. Mirrors inside the device amplify that light and force the waves to move together in a single direction, creating a narrow, focused beam that can travel long distances without spreading out.

📚 The long answer

Regarded by cats and dogs as the most elusive prey, laser pointers are a fascinating display of physics at work.

But before we get into the technology of laser pointers, let's first nail down what exactly is a laser.

What are lasers?

If you compare a laser pointer to a flashlight, you'll notice a few key differences. While both produce light going in one direction, a flashlight's white light spreads out the further it is directed. A laser pointer, however, produces a very narrow, bright beam of single-color light that stays directed no matter how far you point it.

This is what makes lasers special. A laser's light waves are very similar wave lengths (which gives them a single color) and travel in sync, forming a narrow, powerful stream of light.

How do lasers work?

Fun fact: The word "laser" is actually an acronym standing for Light Amplification by the Stimulated Emission of Radiation. This acronym contains clues for how lasers work. 🔎

Let's start with a quick refresher on the basic structure of an atom. An atom contains a nucleus surrounded by orbiting electrons. The electrons are found at fixed distances from the nucleus. As you go farther out, the electrons at higher levels have more energy.

If an electron gets stimulated with extra energy, it temporarily moves up an energy level, and then quickly return to its normal orbit, known as the "ground" state. When the electron returns to its ground state, it releases that extra energy as light.

This is the Stimulated Emission of Radiation part of LASERs. Lasers work by stimulating electrons to release light as they return to their ground state.

Okay, so that's part of the acronym, but what about the LASER part?

Recall that laser light waves move in sync and travel in one direction (Note: I didn't intentionally mean to namedrop two famous boy bands, NSYNC and One Direction, but maybe they should join together to form a band called LASERs).

To achieve this effect, we need to bring in mirrors. A typical laser contains a rod—often ruby crystal—with mirrors on both ends and a flash tube wrapped around it. One side is a full mirror and the other is partially open to allow light to be released.

When you click the button on a laser pointer, the flash tube lights up and provides that initial stimulation of the ruby atoms' electrons.

As the stimulated electrons release light, they stimulate other electrons causing a chain reaction. The mirrors bounce photons back and forth, amplifying the light and keeping it aligned. In short, the mirrors achieve the Light Amplification needed to make lasers work.

Breaking it all down, a laser works because of the physics phenomenon of stimulated electrons releasing light when they return to their ground states. Mirrors are added to amplify the light created in this process and direct the light waves to move together.

If there are any cats or dogs reading this, I hope you now understand the red dot is not your enemy. It’s just physics. Uncatchable, taunting physics.

--- Thanks for reading this week's newsletter! If you have any thoughts, questions, or favorite GIFs, my inbox is always open. Just hit reply to send me a note! :) ​ All my best, Caitlin ​Click here to read five facts about Caitlin​

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​Sources for this week's newsletter​

🌐 Wikipedia article of the week

​Electrical disruptions caused by squirrels​

"Electrical disruptions caused by squirrels are common and widespread, and can involve the disruption of power grids. It has been hypothesized that the threat to the internet, infrastructure and services posed by squirrels may exceed that posed by cyber-attacks."

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👀 Catch up on other curious questions

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