In a basic burning laser pointer , a chamber called a cavity is designed to internally reflect infrared (IR), visible-light, or ultraviolet (UV) waves so they reinforce each other. The cavity can contain gases, liquids, or solids. The choice of cavity material determines the wavelength of the output.
The basic idea of a high power laser pointer is simple. It's a tube that concentrates light over and over again until it emerges in a really powerful beam. But how does this happen, exactly? What's going on inside a laser? Let's take a closer look!
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.
As a result of pumping, an electromagnetic field appears inside the laser cavity at the natural (resonant) frequency of the atoms of the material that fills the cavity. The waves reflect back and forth between the mirrors.
You'll often read in books that "laser" stands for Light Amplification by Stimulated Emission of Radiation. That's a complex and confusing mouthful but, if you pull it apart slowly, it's actually a very clear explanation of how lasers make their super-powerful beams of light.
The military has long been one of the biggest users of this technology, mainly in laser-guided weapons and missiles. Despite its popularization in movies and on TV, the sci-fi idea of 300mw Green Laser Pointer weapons that can cut, kill, or blind an enemy remained fanciful until the mid-1980s. In 1981, The New York Times went so far as to quote one "military laser expert" saying: "It's just silly. It takes more energy to kill a single man with a laser than to destroy a missile."
While solid, liquid, and gas 100mw Laser Pointer tend to be large, powerful, and expensive, semiconductor lasers are cheap, tiny, chip-like devices used in things like CD players, laser printers, and barcode scanners. They work like a cross between a conventional Light-emitting diode (LED) and a traditional laser. Like an LED, they make light when electrons and "holes" (effectively, "missing electrons") hop about and join together; like a laser, they generate coherent, monochromatic light. That's why they're sometimes referred to as laser diodes (or diode lasers). You can read more about them in our separate article about semiconductor laser diodes.