Stuff You Should Know – "How Lasers Work"

Podcast: Stuff You Should Know
Hosts: Josh & Chuck
Release Date: February 12, 2026
Episode Theme:
A deep dive into the science, history, and practical applications of lasers. The hosts break down what lasers are, how they differ from ordinary light, the principles that make them work (including Einstein’s theoretical groundwork), the main types of lasers, and how they show up in everyday life and cutting-edge research. Their trademark blend of curiosity, friendship, and playful humor keeps the episode accessible and fun.

Main Discussion Points & Insights

1. What Is a Laser? (03:05–04:21)

• Definition & Acronym:
  • LASER = Light Amplification by Stimulated Emission of Radiation.
  • The word is an acronym, much like SCUBA, and accurately describes the process.
  • Chuck: “Now that I know what a laser is and how it works, they kind of nailed it with that acronym.” (03:16)
• Lasers in Everyday Life:
  • Found everywhere—from supermarket UPC scanners (that “boop boop” noise) to entertainment and communications tech.
  • Most people are surrounded by invisible lasers daily.

2. Ordinary Light vs. Laser Light (04:51–10:17)

• Spectra and Wavelengths:
  • White light (like sunlight or a bulb) is a mix of many wavelengths/colors.
  • When a prism splits this, you see a spectrum—rainbow colors.
  • Josh: “Within all those nanometer wavelengths…there’s different kinds of yellow. There's a spectrum within the spectrum, I guess.” (06:03)
• Key Differences of Laser Light:
  1. Truly Monochromatic – Light is of a single specific wavelength.
     • “Rather than…570 and 590 for yellow, this is a 572 nanometer wavelength.” (08:35)
  2. Coherent – Photons (light particles) are perfectly in phase, peaks and troughs align.
     • “The photons are perfectly in phase with one another.” (09:09)
  3. Collimated – All light travels the exact same direction.
     • “They’re all traveling in the exact same direction.” (09:40)

3. Einstein’s Theoretical Groundwork (10:28–16:27)

• Planck-Einstein Relation:
  • Einstein proposed that light consists of discrete packets (photons) rather than a continuous wave.
  • Energy of photon = frequency × Planck’s constant (E = hf).
• Spontaneous and Stimulated Emission:
  • Atoms absorb energy, electrons jump up, then return to ground state and “poop out a photon” (prompting laughter from both hosts at this phrasing).
    • Chuck: “Earlier, when I was going over this in my head, I said, poops out a photon.” (13:25)
  • Einstein theorized you could stimulate the process deliberately: “With stimulated emission, you can use a photon to create another photon without losing the first photon.” (14:19)

4. From Theory to Reality – The Birth of the Laser (19:03–23:20)

• Charles Townes and the Maser (1950s):
  • Created a “maser” (Microwave Amplification by Stimulated Emission of Radiation) for microwaves. Later, he and others sought to apply the process to visible light.
• The First Laser (1960):
  • Built by Theodore Maiman using a ruby crystal as the gain medium.
  • The design: sapphire rod “doped” with chromium, surrounded by a flashlamp, reflective end caps.
  • Output: precise ruby-red laser at 694 nm.
    • Josh: “He used a pink ruby crystal as what’s called the gain medium...That’s where the atoms that you get excited are all stored.” (22:20)

5. Five Main Types of Lasers (24:03–34:51)

a. Solid-State Lasers

• Use a solid medium (crystals/doped glass).
• Applications: tattoo and skin cancer removal.
• Doping with rare earth elements (chromium, neodymium, ytterbium) to tweak properties.
  • Josh: “They dope that...to generate photons really efficiently, and they’re gonna generate them in exactly the wavelength you want.” (25:00)

b. Gas Lasers

• Medium: gases like CO₂, argon, krypton.
• Applications: industrial welding, laser cutting, medical surgery (excimer lasers for UV, no heat).
• Pumped by electrical currents.

c. Fiber Lasers

• Use optical fibers as the gain medium, incredibly efficient (>50% electricity conversion).
• Backbone of modern fiber optic communications.
  • Josh: “If you have fiber Internet, you have a laser on one end...sending communications along a fiber optic cable.” (29:52)

d. Liquid (Dye) Lasers

• Use organic dyes in liquid form as the gain medium.
• Tunable over various wavelengths—versatile for specific uses.

e. Diode Lasers (Semiconductors)

• Produce light using electricity flowing across a junction between two materials.
• Most common (laser pointers, barcode scanners, cheap and not powerful).
• Discussion of safety issues: Shining pointers at pilots poses real dangers.
  • Josh: “You are blinding everybody in the cockpit...It’s a huge problem you really should not do.” (33:27–34:06)

6. Amplifying Laser Power: Pulsed Lasers (34:51–37:15)

• Continuous vs. Pulsed:
  • Continuous: steady energy output.
  • Pulsed: Cut the beam to build up energy, then release it in bursts—produces far higher peak power.
  • Early pulsed lasers (1961): produced 100-nanosecond bursts, making beams up to 1000x stronger than the first continuous lasers.
  • Josh: “Your puny brain just sees it as one constant beam of light...we’re talking billions, trillionths, quadrillions quintillionths of a second.” (36:00)

7. The World’s Most Powerful Lasers (39:12–40:47)

• ZEUS (Univ. of Michigan) and Vulcan (UK):
  • Pushing peak power to study black-hole-like environments and fusion.
  • Vulcan: as powerful as “500 million 40 watt light bulbs.” (39:33)
  • ZEUS: 3 petawatts in 25 quintillionths of a second—“100 times the total electrical output of the entire world in one quick burst.” (39:56)

8. Lasers in Nuclear Fusion (40:47–42:10)

• Breakthrough at Lawrence Livermore (2022):
  • 192 lasers used to initiate fusion, achieving “net gain” (more energy out than in)—called “the Wright brothers moment” of fusion.
  • Chuck: “They focused those lasers at a capsule the size of a peppercorn, and that did it.” (41:51)
  • If scalable, this could change energy forever.

9. Real World Applications (42:10–46:32)

Everyday Uses

• Barcodes, CD/DVD players, fiber optics—“Lasers are everywhere.”
• Anything that can absorb/bounce light could use lasers.

Medical Industry

• Surgical Lasers: Precision cutting, cauterization, self-sterilizing, reduced blood loss, quicker healing.
• Tiny Incisions: Brain tumor removal with a 5mm hole; discharge possible the next day. (43:11)
• Endoscopy: Lasers on fiber-optic tubes reach tough spots—tumor shrinking, ablation.
• LASIK Eye Surgery: Laser reshapes cornea for improved vision.
  • 90% achieve 20/20–20/40.
  • Josh: “It’s pretty safe and effective...I would do it, I’m just not there yet.” (46:09)

Weapons Development

• Military developing “directed energy systems” for drones, not personnel.
• Deployment on ships (turrets) and vehicles (e.g., Stryker vehicle)—with mixed efficacy due to the need for stability and focus.

Science & Research

• Laser Cooling/Particle Traps:
  • Lasers can “freeze” atoms in space using the recoil from emitted photons—enabling ultra-precise measurement (e.g., atomic clocks).
  • “It’s like a tractor beam holding it where you want it.” (48:49)
• Environmental Monitoring: Soil moisture, ice cap recession tracked from space via lasers.

Notable Quotes & Memorable Moments

• Chuck: “Uncle Josh likes it. That’s like talk to the hand, but way better.” (02:59) — On a niece’s hand gesture, showing the hosts’ trademark wit.
• Josh: “Labseor doesn’t… have the same ring to it as laser. Throw me the labseor gun.” (03:51) — Goofing on acronyms.
• Chuck (regarding photons): “It poops out that photon.” (13:25) — Silly, memorable phrasing.
• Josh: “When you have subatomic particles, like an electron orbiting an atom...when a photon hits it, that electron goes up in energy, I think for like 100 nanoseconds, typically.” (12:16)
• Josh (on pulsed lasers): “Your puny brain just sees it as one constant beam of light.” (36:00)
• Josh: “If you have fiber Internet, you have a laser on one end…” (29:52)
• Chuck: “You’re blinding everybody in the cockpit. It’s a huge problem you really should not do.” (34:06) — On dangers of laser pointers.
• Josh: “Once we get to nuclear fusion, that’s going to change absolutely everything.” (42:07)
• Chuck: “Turns out using a laser to cut into the human body is way better than a scalpel.” (42:53)

Timestamps for Key Segments

• 03:05–04:21 – What is a Laser? Acronym and real-life presence
• 04:51–10:17 – Ordinary vs. laser light, three key differences
• 10:28–16:27 – Einstein, Planck, and the physics behind lasers
• 19:03–23:20 – Charles Townes, masers, the first ruby laser
• 24:03–34:51 – Five main types of lasers and real-world examples
• 34:51–37:15 – Pulsed lasers, their power and mechanics
• 39:12–40:47 – ZEUS, Vulcan: mind-bogglingly powerful lasers
• 40:47–42:10 – Lasers making nuclear fusion possible
• 42:10–46:32 – Medical, industrial, communication, and research uses

Language & Tone

The hosts keep it conversational, accessible, and witty—even when tackling technical subjects. Jokes about “pooping out photons,” playful banter, and self-deprecating humor (admitting past ignorance of how lasers actually work) are threaded throughout.

Conclusion

Josh and Chuck deliver a thorough yet entertaining overview of lasers, from the physics basics to applications as mundane as supermarket scanners and as world-changing as nuclear fusion. You’ll leave knowing not only “how lasers work” but also how this technology has shaped, and will continue to shape, our daily lives and most ambitious scientific pursuits.

If you’ve ever taken a laser pointer for granted or had your mind blown by a fiber connection, this episode will make you appreciate the elegant, Einstein-paved science and engineering behind all those beams of light.