Lasers are classified based on their gain medium and mode of emission

Stimulating electrons to emit identical photons produces lasers

This effect was predicted by Albert Einstein in 1917, and requires all excited electrons in a material to exist in the same excited metastable state within their atoms. Pumping all atoms through the same mechanism, such as electricity or flash lamps, can create this environment.

Some materials can absorb low-energy light and emit high-energy radiation

Through anti-Stokes cooling, incoming energy is combined with vibrations in a material's crystal lattice to produce a net reduction in its temperature. Using this effect, lasers can be directed at microchip hot spots to help keep data centers cool.

Laser technology powers communication, medical and manufacturing tools

Lasers are used when scanning groceries, printing documents or undergoing cosmetic procedures to enhance efficiency, precision and accuracy. Missile defense, targeting and optical communication systems have made using laser technology habitual in the military.

Fiber lasers used for metal engravings can’t burn your skin

These devices use diodes and mirrors to create pulses of light that vaporize metal in billionths of a second, though at wavelengths that cannot react with organic material. Pulse width, power, and speed adjustments can produce white, black, and even colored patterns through controlled heat reactions.

The different energy levels of each element result in unique colors when burned

When heated, electrons absorb energy and move to excited states within an atom. They promptly drop back down and release light energy corresponding to the size of the drop, which is unique to each element.

Random lasers can be created from biomaterials, such as peanuts and birch leaves

Rather than creating a narrow beam of light via amplification in an optical cavity, the random laser produces a red glow by scattering photons created in the natural pores of a peanut kernel after it has been injected with a solution of light-generating carbon dots derived from birch leaves.

View the electromagnetic spectrum and the properties of different types of light

All forms of electromagnetic radiation, from radio waves to gamma rays, travel at the speed of light in a vacuum, but their wavelengths decrease as their frequencies increase. The light-sensitive nerve cells in the human eye are sensitive to a narrow range of values, which we observe as the spectrum of visible light.

Laser-etched electric charges guide toner during laser printing

When sending a print job, the file data generates an image that a laser maps positively charged regions onto a drum separately for each color toner. Once the negatively charged toner is applied where it was electrically attracted, heat and pressure fuse it onto the paper.

Removal of different color tattoo inks may require multiple lasers

Light needs to be absorbed by ink particles to break them down into small enough pieces for the immune system to eliminate. Color ink reflects, rather than absorbs, lasers of the same color, while black ink absorbs all colored lasers.

Variations in the energy of light force the use of multiple telescopes

Just as Earth's atmosphere allows the sun's visible light to pass through while blocking other harmful radiation, telescope mirrors and other optics can only reflect, absorb, or transmit certain types of light. Detectors also utilize semiconducting materials that react to specific energies of light, thereby preventing a one-telescope-fits-all solution.

How helium greatly improves the efficiency of barcode-scanning lasers

Rather than directly energizing neon atoms, electrical discharge at lower, more practical power levels can excite helium atoms to energy levels nearly equal to those in neon atoms. Within a helium-neon laser, these gases are present in a 10-to-1 ratio, enabling helium to efficiently transfer energy to neon, which is then discharged as red light.

Laser disc technology stores binary data in etched pits and lands

The pits are dips in the LaserDisc, CD, DVD, or Blu-ray surface that do not reflect the laser from the optical drive back to the photoelectric cell, resulting in a coded zero. Lands are reflective plateaus on the surface that code for a one.

Chromium contaminants in a ruby crystal gave the world's first laser its red color

The red light originates from a long-lasting excited electron state in the element's atomic structure. The brittle gray metal has historically been used in pigment production, the manufacturing of rust-resistant stainless steel, and the creation of durable coatings with long-lasting shine for metals, wood, and leather.

The reflection of light within a material is the basis for fiber optics

As light travels from one material to another, it can be absorbed, reflected, or transmitted through, depending on the properties of the two materials. Fiber optic cables are designed to reflect light internally, minimizing data loss as information is sent at high speeds through flashes that represent zeros and ones.

Solar sails use light as a means of propulsion

Photons possess momentum and can transfer it to objects they strike or bounce off, imparting radiative pressure, or a light-based force over a small surface area. Lasers fired at observational equipment with specially designed sails can theoretically use this mechanism to accelerate up to 20% the speed of light.

Bioluminescence produces new light while biofluorescence re-emits absorbed light

A chemical reaction between luciferin and oxygen—catalyzed by luciferase—produces light within bioluminescent organisms. Biofluorescence, on the other hand, involves special proteins that absorb light of one wavelength and re-emit the light at a different, typically longer, wavelength.

Credit for inventing the laser was fought over for nearly three decades

Although Theodore Maiman built the first working laser in 1960, Gordon Gould coined the term earlier. Charles Townes and Arthur Schawlow of Bell Labs filed a patent after Gould came up with the idea and name, but before Gould filed his patent.

Gravitational waves are detected at LIGO by measuring shifts in interfering lasers

The instruments at each site send lasers down equally long arms, which should take the same amount of time to travel between suspended mirrors. Passing gravitational waves alter the shape of space—lengthening one arm and shrinking the other—altering how long it takes the lasers to complete their path, which scientists can measure.

LEDs emit pure colors, while incandescent bulbs filter white light

Traditional Christmas lights produce softer, less saturated colors by partially blocking the full spectrum of light, resulting in a particularly warm glow by dimming the cooler blue tones. LEDs are designed to emit a single wavelength of light, creating intense colors that are visually unbalanced in multicolor environments.

The most common type of particle accelerator is a linear electron accelerator

Known as linacs, these devices fire particles in a straight line, making them useful for the intense, targeted beams needed in cancer treatment. Circular accelerators, such as synchrotrons and cyclotrons, can achieve extremely high particle speeds through repeated exposure to electromagnetic fields.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

The science behind why some noises have color names

Different noise colors (white, brown, pink, blue) have been proven to affect mood and focus. An audiologist explains that these sounds are named after specific light wave frequencies. While individual preferences vary, certain noises consistently impact sleep, stress reduction, cognitive performance, and problem-solving. The article highlights how these sounds can enhance productivity, relaxation, and even gaming experiences.

A diamond's color comes from impurities, defects, and unique formation processes

While most diamonds are transparent and sparkly, the presence of nitrogen and boron during formation can make them yellow, orange, or blue. Radiation can produce green diamonds, and structural deformities can introduce red hues.

Neutron star types, categorized by the presence of strong magnetic fields and radiation beams

Magnetars have magnetic fields about 1,000 times stronger than the average neutron star—roughly a trillion times stronger than Earth's. Pulsars emit beams of radiation from their magnetic poles, which appear as flickering radio wave signals as the object spins.

View a gallery of various auroral shapes

Auroras can be generally classified as discrete (well-defined shapes) or diffuse (hazy shapes), with light taking various forms, including curtains, arcs, pillars, and rays. Some auroras can also pulsate, particularly after intense periods of auroral activity are winding down.

Capital assets include investments from stocks to fine jewelry

Capital assets can be classified as property owned and used for personal or investment reasons. If a capital asset grows in value and the holder decides to sell it, their “capital gains” would be roughly the difference between the original purchase price and the amount of money they sold the asset for.

Massive blooms of microscopic plankton called dinoflagellates produce the neon blue light seen in glowing tides.

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

Neutron stars, the remains of some massive stars after they explode in a supernova, are the densest directly observable objects in the universe.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Memecoins are a type of cryptocurrency—a form of digital currency with a wide variety of uses—created around popular 'memes,' or viral internet jokes.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

Sony set the standard for cylinder-shaped batteries when it repurposed manufacturing equipment used to make rolls of magnetic recording tape.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

Hedge funds, the private investment firms that trade a wide swath of financial assets, make money by imposing steep fees on investors and from the fund's investment performance.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

Louisiana's 'Cancer Alley' is infamous for having some of the highest industrial pollution, toxic air emissions, and cancer risks in the US.

The Mona Lisa's celebrity status and repeated restorations have obscured what made the painting so revolutionary for its time

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

Ebola is a filovirus, meaning it resembles a thread under a microscope, though it sometimes twists and can resemble a bowl of spaghetti.

This poison ivy knowledge quiz—accompanied by photos of the plant's varied forms—may help you identify this common rash-inducing growth.