What is Laser and how do it work ?

A small pulse of laser light “tuned” to the excited electrons’ energy is directed through the glass slabs.

This laser pulse stimulates the electrons to drop to their lower, or ground, energy states and emit a laser photon of exactly the same wavelength.

An optical switch traps the low-energy laser pulse in the main amplifier for four passes through the laser glass slabs.

Even so, defense scientists have continued to transform laser-based missiles from science fiction into reality.

Mirrors at both ends of the glass amplifier cause the photons to travel back and forth through the glass, stimulating more electrons to drop to their lower energy states and emit photons.

This process produces huge numbers of photons of the same wavelength and direction—an extremely bright and straight beam of light.

The US Navy first began testing LaWS (Laser Weapon System) onboard the USS Ponce ship in the Persian Gulf in 2014.

In this way the initial low-energy pulse is amplified by more than a quadrillion times to create 192 highly energetic, tightly focused laser beams that converge in the center of the Target Chamber.

Using solid-state lasers pumped by LEDs, it was designed to damage or destroy enemy equipment more cheaply and precisely than conventional missiles.

Lasers can be tiny constituents of microchips or as immense as NIF, which is ten stories high and as wide as three football fields.

The tests proved successful, and the Navy announced contracts to build more LaWS systems in 2018.

Lasers are found in a dazzling range of products and technologies, including CD and DVD players, metal-cutting machines, measuring systems, and eye and cosmetic surgery.

Early lasers could produce peak powers of some 10,000 watts.

Meanwhile, the development of space lasers continues, though none have so far been deployed.

Modern lasers can produce pulses that are billions of times more powerful. Scientists have demonstrated NIF’s ability to generate more than 500 trillion watts of power.

Some lasers, such as ruby lasers, emit short pulses of light. Others, like helium–neon gas lasers or liquid dye lasers, emit light that is continuous.

NIF, like the ruby laser, emits pulses of light lasting only billionths of a second.

We can trace the birth of lasers right back to the first two decades of the 20th century. That's when Albert Einstein figured out the quantum theory of light and photons (in 1905) and the mechanism of stimulated emission (in 1917)—the two key components of laser science.

Laser light does not need to be visible.

it was another four decades before the first practical laser actually appeared.

NIF beams start out as invisible infrared light and then pass through special optics that convert them to visible green light and then to invisible, high-energy ultraviolet light for optimum interaction with the target.

Lasers evolved from masers, which are similar but produce microwaves and radio waves instead of visible light.

Masers were invented in the 1950s by Charles Townes and Arthur Schawlow, both of whom went on to win the Nobel Prize in Physics for their work (Townes in 1964 and Schawlow in 1981). They applied to protect their invention on July 30, 1958 and were granted US Patent #2,929,922 (Masers and maser communication system) on March 22, 1960 (you can see one of the drawings from it here).

But did they invent the laser? In 1957, one of Townes' graduate students, Gordon Gould, sketched in his lab notebook an idea for how a visible light version of the maser could work, coining the word "laser" that we've used ever since. Unfortunately, he didn't patent his idea at the time and had to devote the next 20 years of his life to legal battles, eventually gaining a patent for part of the laser invention (Method of energizing a material) and substantial back royalties in 1977.

Although Townes and Schawlow are often credited with inventing lasers, the first person to build a working, visible light laser was actually Theodore Maiman, who has never really gained the recognition he deserved: his original writeup of his work was rejected by the journal Physical Review Letters and, despite twice being nominated for the Nobel Physics Prize, he never won the ultimate accolade.