How Lasers Work

What It Covers

This episode explains how lasers work, from Einstein's 1917 theoretical foundation of stimulated emission to modern applications. The hosts break down laser physics including monochromatic light, coherent photons, and gain mediums, then explore five laser types and real-world uses from medical procedures to nuclear fusion experiments.

Key Questions Answered

• •Einstein's Stimulated Emission Theory: Albert Einstein theorized in 1917 that photons can stimulate atoms to produce identical photons without losing the original photon, creating a cascading effect. This differs from spontaneous emission where one photon gets absorbed and one released. Stimulated emission enables photon multiplication, forming the foundation for all laser technology and explaining the SE in laser's acronym.
• •Three Critical Laser Properties: Laser light differs from regular light through monochromatic wavelength (single specific wavelength like 572 nanometers instead of 570-590 range), coherent photons (peaks and troughs perfectly aligned without interference), and collimated direction (all photons traveling identically). These three properties allow photons to combine tightly without disruption, creating concentrated beams impossible with natural light sources.
• •Pulsed Laser Power Amplification: Pulsed lasers achieve exponentially higher power by stopping the beam in bursts measured in nanoseconds to quintillionths of seconds, allowing energy to build behind the blockage. The University of Michigan's ZEUS laser generates three petawatts per pulse, equivalent to 100 times Earth's total electrical output. This technique enables applications from nuclear fusion to recreating conditions inside stars.
• •Medical Laser Precision Benefits: Surgical lasers cut through five millimeter skull holes for brain tumor removal with next-day discharge, demonstrating superior precision over scalpels. Lasers self-cauterize tissue, reduce blood loss, sterilize surrounding areas, and enable faster healing. LASIK eye surgery achieves 20/20 to 20/40 vision in 90 percent of patients by reshaping corneas with laser precision impossible through traditional methods.
• •First Laser Construction 1960: Theodore Maiman built the first functional laser using a pink ruby crystal as gain medium, surrounded by coil-shaped flashbulb pump, with reflective silver-painted ends. The ruby crystal produced photons at precisely 694 nanometers wavelength. Within one year, scientists achieved 100 nanosecond pulse bursts, making lasers 1,000 times more powerful than Maiman's original continuous beam device.