Everything Everywhere Daily: History, Science, Geography & More - All About Lasers

Episode Date: September 4, 2022

In 1917, Albert Einstein published a paper whereby he proposed a new method of creating light based on the principles of quantum physics. Over 40 years later, researchers finally put Einstein’s ideas into practice. For years it remained a solution in search of a problem. Today, the number of applications for this source of light is almost limitless and includes everything from nuclear fusion, to annoying cats.  Learn more about Light Amplification by Stimulated Emission of Radiation, or LASERs, on this episode of Everything Everywhere Daily. Subscribe to the podcast!  https://link.chtbl.com/EverythingEverywhere?sid=ShowNotes -------------------------------- Executive Producer: Darcy Adams Associate Producers: Peter Bennett & Thor Thomsen   Become a supporter on Patreon: https://www.patreon.com/everythingeverywhere Update your podcast app at newpodcastapps.com Search Past Episodes at fathom.fm Discord Server: https://discord.gg/UkRUJFh Instagram: https://www.instagram.com/everythingeverywhere/ Facebook: https://www.facebook.com/EverythingEverywhere Twitter: https://twitter.com/everywheretrip Website: https://everything-everywhere.com/everything-everywhere-daily-podcast/ Everything Everywhere is an Airwave Media podcast." or "Everything Everywhere is part of the Airwave Media podcast network Please contact [e-mail] to advertise on Everything Everywhere. Learn more about your ad choices. Visit megaphone.fm/adchoices

In 1917, Albert Einstein published a paper whereby he proposed a new method of creating light based on the principles of quantum physics. Over 40 years later, researchers finally put Einstein's ideas into practice. For years, there remained a solution in search of a problem. Today, however, the number of applications of this source of light is almost limitless and includes everything from nuclear fusion to annoying cats. Learn more about light amplification and stimulated emission of radiation, or lasers. on this episode of Everything Everywhere Daily.

What if your perceptions about the past were wrong? ThruLine is a podcast that takes you back in time to uncover the parts of the story that may have gone unnoticed. It effectively turned day into night. And how it shaped the world now. Time travel with us every week on the ThruLine podcast from NPR. The development of lasers dates back to the beginnings of the 20th century, with the development of quantum physics.

One of the groundbreaking ideas behind quantum physics was that light could be emitted or absorbed in discrete units that were called quanta. Before I go any further, I should explain how light is produced at a very basic level because it's necessary to understand how lasers work. Each atom has electrons orbiting around it at different levels. Technically, they're more probabilistic clouds, but for the purposes of this discussion, you can think of them as different orbital levels. When all the electrons in an atom are at the lowest orbits possible, it's known as the ground state. When photons are captured by electrons, it kicks the electrons up to a higher orbit, putting them at a new energy level and out of the ground state. This is sort of like when you roll a ball up a hill. The ground state for the ball is at the bottom of the hill.

When you put it at the top of a hill, you've added energy. And if something disturbs the ball, it's going to want to roll back downhill. So, too, does the electron want to go back down to? its ground state. When it does this, depending on what level it was at, it will emit a photon, a.k.a. it will emit light. Normally in something like a light bulb, the electricity kicks the electrons up a level, and then they come back down to its ground state somewhat randomly. The result is photons of many different wavelengths, aka colors, with many types of polarization, being emitted in many different directions. All of these photons being created without any sort of

order is known as incoherence. And this is how almost all light is created, both naturally and artificially. Einstein posited that it might be possible to create a system where all the light which was created would be coherent through a quantum physics phenomenon known as stimulated emission. More on that in a bit. The idea of stimulated emission was just an idea for years until work began on actually trying to implement the ideas in the 1950s. The first device which used stimulated emission was constructed by a team led by Charles Hard Towns, which amplified microwaves. They dubbed their device a mazer, an acronym that stood for microwave amplification by stimulated emission of radiation. The device was seriously limited in what it could do,

but it was a huge step forward that proved that it could be done. In the late 1950s, many teams around the world were trying to create what was then called an optical mazer. The term laser, replacing the M in microwaves for the L in light, was dubbed in 1957 by a Columbia University graduate student named Gordon Gould. Here I should note that while laser is technically an acronym, like radar or sonar, its usage has become so common that it's usually not capitalized anymore. Gould came up with a host of possible uses for lasers and filed a patent for lasers in 1960. His patent was actually denied and was given to Bell Labs, who, if you remember from previous episodes, invented everything. He spent the next 27 years fighting for the patent before finally winning in

1987. However, the first group to make a working laser was led by Theodore Mimon at the Hughes Research Laboratories in Malibu, California. The laser used a synthetic ruby crystal as its medium, and produced light at a wavelength of 694 nanometers. So here I will try to explain exactly what this stimulated emission is and what makes a laser a laser and different from, say, a flashlight. In stimulated emission, light of a very particular type is created inside the laser. The photons in the laser medium tend to cause the atoms inside the laser medium to release photons that are just like the photons that are already there. There is a quantum effect whereby photons want to be with other similar photons. So the new photons have the same wavelength, direction, and polarity as the original photons.

In other words, the light is coherent. These new photons create even more amplifying the creation of the light inside the chamber. The chamber has mirrors on both ends, allowing light to bounce back and forth, but one of the mirrors allows a small amount of light to pass through. The creation of a single type of light that is coherent in direction, polarity, and wavelength is what makes a laser a laser. And why, just poking a tiny hole in a box with a light bulb will not get the same result. A laser's wavelength of light is determined by the active laser medium or the gain medium inside of the laser. The first laser, for example, used a synthetic ruby, but you could use many different substances,

and they could be a solid, a gas, or a liquid. In December of 1960, Bell Labs created the first gas laser, which is a laser where the medium was a mix of helium and neon. The discovery of lasers made for great press. They were suspiciously like death rays from science fiction stories, and one of the first mentions of lasers in popular culture was in the 1964 movie Goldfinger, where James Bond is tied to a table and threatened to be cut in two by a laser. Despite the early excitement about lasers, they had few practical applications at first, which is really surprising given how many

thousands of applications for lasers there are today. But it didn't take long for lasers to find a multitude of uses. In 1961, the first medical treatment was performed with a laser. It was used to destroy a tumor inside of a retina. In 1962, groups at General Electric, IBM, and MIT, almost all simultaneously developed a semiconductor laser, which is a type that's used in many different forms of electronics. In 1964, the carbon dioxide laser was developed that used CO2 as the active medium. CO2 lasers are extremely powerful because the light wave that they create is in the infrared wavelength,

which is radiant heat. CO2 lasers were some of the first lasers used for industrial cutting. In 1966, British physicist George Cow and his team determined how to send information via lasers across fiber optic cables. He was actually awarded the 2009 Nobel Prize for his work on fiber optic communications. Today, lasers using fiber optic cables transmit almost all of the Internet's data and are responsible for an ever larger percentage of bandwidth to people's homes. In 1969, Apollo 11 took with him to the moon a special print. prism called a retro reflector, designed to reflect light directly back from any angle from which it

came. The purpose of the prism was that a laser would be aimed at it, and a few of the photons would then be bounced back directly to the laser. They could then measure the time it took for the photons to make the round trip, and from that they could use the speed of light to measure the distance to the moon. And they've been doing this technique to measure the distance to the moon now for almost 50 years, and it's accurate to within a few centimeters. In 1974, the first laser barcode scanner was deployed in a supermarket. The scanner could quickly read a barcode, which I've done a previous episode on, and then use the scan data to interface with a computer.

In 1982, one of the very first commercial uses of lasers, and the one which gave most people a personal exposure to them, was the release of the audio compact disc, or CD. The CD worked by a red laser with a wavelength of six. 650 nanometers, shining on a spinning disk, which would then reflect light off of the pits in the disc. The pits were binary ones or zeros, which could then decode the digitally encoded music. Blu-ray discs were literally just a change in the lasers to a blue violet laser with a 405 nanometer wavelength. The shorter wavelength of light allowed for smaller pits on the disc, which allowed for higher data density. In 1985, David Chu did work on lasers to manipulate atoms, allowing him and his team to set up.

records for the lowest temperatures ever recorded. Chu won the Nobel Prize for his work, and was later the U.S. Secretary of Energy. As lasers became more powerful, their potential applications expanded into the realm of the military. Extremely powerful lasers had been developed that could shoot down rapidly moving missiles out of the sky. And another use of high-powered lasers is in the development of nuclear fusion. If several high-powered lasers can be focused on the exact same spot, it can create temperatures high enough to ignite fusion. Less powerful military lasers were developed to measure distances for aircraft and cruise missiles, and still other lasers could use their straight-line capabilities to aim a rifle.

One ever-growing use for range-finding lasers is called LiDar. It stands for Laser Imaging Detection and Ranging, and uses lasers to create a 3D map of the terrain at seas. There are a host of LIDAR uses, including getting accurate maps of buildings. Much of the reconstruction done on the Notre Dame Cathedral in Paris is possible due to the fact that there are high-quality 3D models of it, which had been created beforehand using LiDAR. Likewise, LiDR is used as the navigation system for projects attempting to create self-driving cars. Lider allows an onboard computer to get an accurate 3D map of the car

surroundings. I'll end by discussing one of the uses of lasers which many of you have had direct experience with, laser pointers. The availability of commercial laser pointers is a testament into just how cheap and available lasers have become. It's now actually possible to find cheap laser pointers for about $10 on Amazon. Many colors are available, but the most common are red and green. Red has the longest wavelength, and they tend to be cheaper and easier to make. Green is often used when doing outdoor astronomy, simply because green appears to be brighter for the same amount of energy to our eyes.

Despite being very low power, shining a laser pointer directly into someone's eyes can be incredibly dangerous. Because of how concentrated the light is, it's actually more dangerous than staring directly into the sun. Lasers have so many uses it would be impossible to list them all. Almost every sector of the economy, from medicine to communications to agriculture to transportation, uses lasers to one degree or another. Its widespread use across so many different areas has made the laser one of the most important inventions of the last 100 years. Everything Everywhere Daily is an Airwave Media podcast. The executive producer is Darcy Adams.

The associate producers are Thor Thompson and Peter Bennett. I just wanted to extend a big thank you to everyone who is supporting the show over at Patreon.com. I have show merchandise available there, including hoodies, t-shirts, and stickers. Plus, it really just helps me get this show out every single day, including, of course, weekends and holidays. Remember, if you leave a review or send me a boostagram, you too can have it read on the show.