Have you ever had a chance to see a laser light show? These captivating displays feature laser light beams that flash through the air and sometimes form pictures on surfaces. A laser is a device, which has the unique ability to produce highly concentrated light of one color and wavelength. Laser light is different from non-laser light in various ways. One of the most important differences is that laser light is coherent. When light is coherent, it possesses a remarkable property, light waves move together as they travel away from their source. The crests and troughs of coherent light waves line up in a position, and the individual waves behave as one single wave. In this article, we will learn about laser light and how laser is produced.

The term "laser" stands for Light Amplification by Stimulated Emission of Radiation. Amplification is the increase in the brightness of the light.

The concept of stimulated emission is a fundamental aspect of the behavior of light and atoms. Within an atom, electrons can transition between different energy levels, and this transition triggers the release of a photon when an electron moves from a higher energy level to a lower one. This photon release process is termed emission.

Stimulated emission, on the other hand, is a specific occurrence that takes place when a photon strikes an atom in an excited state and makes that atom emit another photon. It's important to note that the newly emitted photon is an exact duplicate of the initial photon, and they travel away from the atom together. The mentioned figure shows how stimulated emission works to produce laser light.

This is the heart of the laser. It's a material (solid, liquid, or gas) that can amplify light by stimulating the emission of photons. The gain medium determines the color of the laser.

Lasers need an external energy source to pump energy into the gain medium. This energy source can be a flashlamp, an electric discharge, or another laser.

The optical resonator consists of two mirrors, one at each end of the gain medium. These mirrors are highly reflective, allowing light to bounce back and forth inside the resonator.

One of the mirrors is partially reflective, allowing a portion of the laser light to exit as the laser beam.

Laser light possesses several unique characteristics that set it apart from regular light sources:

Laser light is composed of a single color or wavelength. This monochromatic nature is a result of the gain medium's properties.

The light waves in a laser beam are in phase, meaning they have a consistent and uniform pattern. This coherence allows laser light to be focused on a tight beam.

Laser beams are highly directional, and their divergence angle is very small. This means they can be focused to a point over long distances, making them ideal for applications like laser pointers and long-range communication.

Laser light can be incredibly intense, with power densities that can cut through materials or perform precise surgeries.