49 Fun Facts About Laser

In the acronym 'laser', what do the letters S and E stand for?

Stimulated emission: a passing photon triggers an excited atom to release an identical photon, so light bouncing between two mirrors multiplies in perfect step.

Who built the first working laser, in 1960?

Theodore Maiman: when the feat was announced in July 1960, one Los Angeles newspaper headlined it as the discovery of a science-fiction death ray.

The first working laser used a synthetic crystal of which gemstone as its lasing medium?

Ruby: a leading laser theorist had publicly said pink ruby would take too much energy to work as a laser, yet a flash-lit pink ruby rod gave off the first laser light.

The maser, the laser's predecessor, amplified what kind of radiation?

Microwaves give the maser its M, and the name 'laser' was made simply by swapping that first word for 'light'.

Which physicist laid the theoretical foundations for the laser in a 1917 paper on the quantum theory of radiation?

Albert Einstein worked out the idea more than 40 years before anyone built a laser, and his own Nobel Prize honoured quite different work, on the photoelectric effect.

Charles Townes shared the 1964 Nobel Prize in Physics with two scientists from which country?

The Soviet Union: Nikolay Basov and Aleksandr Prokhorov, in Moscow, had reached the same idea independently and at the same time as Townes in New York, on opposite sides of the Cold War.

What did Gordon Gould do with the 1957 notebook in which he coined the word 'laser'?

Had it notarised: the stamped pages became his main evidence in a patent battle that dragged on for decades, until he finally prevailed in 1987.

Astronomers at giant telescopes fire lasers into the night sky to create artificial versions of what?

Stars: the beam makes a spot glow high in the atmosphere, and the telescope watches that fake star to measure the air's blurring so a flexible mirror can cancel it out.

Gordon Gould delayed patenting his laser design, and lost decades in court, because he wrongly believed he first needed what?

A working prototype: no such rule existed, and by the time he applied in 1959 a rival application was already in. His first laser patent did not arrive until 1977.

Which journal published the report of the first working laser in 1960, after Physical Review Letters turned it down?

Nature printed the short report on 6 August 1960. Charles Townes later judged it perhaps the most important paper per word that the journal published in a century.

The first gas laser, built at Bell Labs by Ali Javan's team, ran on a mixture of which two gases?

Helium and neon: the first laser could fire only in brief pulses, but this glowing gas tube produced the first continuous beam.

The earliest semiconductor lasers, demonstrated by rival American teams in 1962, were made of which material?

Gallium arsenide: unlike the silicon of ordinary chips, it turns electric current into light efficiently, which is why the rival teams at General Electric and IBM both chose it.

Kumar Patel's 1964 laser, long the factory workhorse for cutting and welding, gets its beam from which gas?

Carbon dioxide: it turns up to a fifth of its input power into beam and can run continuously at many kilowatts, which made it the obvious tool for slicing sheet metal.

Laser hair removal works best on which combination of hair and skin?

Dark hair, light skin: pigment soaks up the beam's heat, so a dark hair cooks at the root while the pale skin around it stays cool. Blond, grey and white hairs hold too little pigment to heat up.

When it was first invented, the laser was famously described as what?

Gould's notebook had already listed telecommunications, radar, spectrometry and nuclear fusion as possible uses.

The seabed cables that carry the internet as pulses of laser light are mostly about as thick as what?

A garden hose: nearly all data crossing the oceans squeezes through cables that slim, and the fibres inside, where the laser pulses actually travel, are no wider than a human hair.

The first product ever scanned with a UPC barcode at a supermarket checkout was a pack of what?

Chewing gum: a 10-pack of Wrigley's Juicy Fruit, scanned just after 8 a.m. on 26 June 1974 in Troy, Ohio, a town chosen because the maker of the checkout equipment was based nearby.

Which two electronics companies jointly developed the compact disc, read by a laser instead of a needle?

Philips and Sony: the Dutch and Japanese firms agreed a single shared standard in 1980, so every disc would work in every machine, and sales began two years later.

The laser printer was invented by Gary Starkweather while he worked at which company?

Xerox: Starkweather rigged a laser onto one of the firm's office copiers so it could 'draw' pages straight from a computer, and the printers that followed earned the company billions.

Which type of laser reshapes the cornea in LASIK eye surgery?

Excimer: its ultraviolet pulses break down only an extremely thin surface layer, so the cornea can be shaved a sliver at a time with almost no heating of the tissue beneath.

Which type of laser is by far the most commonly made, found in barcode readers, pointers and disc drives?

Diode lasers are semiconductor chips that turn electric current straight into light. Small and cheap to make, they also drive the world's fibre-optic links.

Which technology maps its surroundings by timing laser pulses as they bounce back?

Lidar: the word was modelled on 'radar', with light doing the job of radio waves, and dictionaries date it to the early 1960s, just after the laser itself appeared.

The first reflector for bouncing laser beams off the Moon was left there by which mission?

Apollo 11: the crew left a panel of 100 small mirrors in the dust, and observatories were still bouncing laser pulses off it half a century later.

Lasers bounced off the Moon show it drifting away from Earth about as fast as what grows?

Fingernails: about 3.8 centimetres a year. Timing a laser pulse's two-and-a-half-second round trip fixes the Moon's distance to within a few millimetres, so even that slow drift shows up.

In which US state do the 192 laser beams of the National Ignition Facility converge on a tiny target?

California: the facility sits at Lawrence Livermore National Laboratory, where its beams recreate in miniature the conditions inside an exploding nuclear weapon.

On 5 December 2022 the National Ignition Facility achieved what long-sought milestone?

Scientific breakeven for fusion: after six decades of trying, the fuel at last gave out more energy than the laser pulse put in, about 3 megajoules for 2, by copying the reaction that powers the Sun.

LIGO's laser beams can detect its 4-kilometre arms changing length by one ten-thousandth of the width of what?

A proton: to reach that precision, mirrors bounce each beam back and forth along the arms hundreds of times, stretching the light's path to more than a thousand kilometres.

LIGO's first detection, on 14 September 2015, came from the merger of two of what?

Black holes: the pair collided about 1.3 billion years ago, and the ripple they sent through space took all that time to reach LIGO's laser beams.

The 1997 Nobel Prize in Physics went to Steven Chu and two colleagues for using lasers to do what?

Cool and trap atoms: light normally warms things, but beams tuned just right slow atoms from thousands of kilometres an hour almost to a standstill, which is the same as chilling them.

In the film Goldfinger a laser creeps towards James Bond, but what threatens him in Ian Fleming's original novel?

A circular saw: the novel came out in 1959, a year before the first laser was built, so the film-makers swapped in the brand-new invention to make the scene feel fresh.

In the Austin Powers films, Dr. Evil demands which sea creatures 'with frickin' laser beams attached to their heads'?

Sharks: he has to wait until the third film, when his son finally presents him with a tank of them, lasers and all.

Which colour of laser pointer looks brightest at the same power, because human eyes are most sensitive to it?

Green: the eye's sensitivity peaks there and falls away towards red and blue. In many green pointers the beam starts out as invisible infrared, which cheap ones sometimes let leak.

Which part of the eye does the visible beam of a laser pointer damage most readily?

The retina: the eye's own lens focuses the beam to a pinpoint there, concentrating its power enormously. Ultraviolet beams are absorbed at the front of the eye and harm the cornea instead.

Which of these is rated a Class 1 laser product, the safest category?

A CD player: its laser is sealed inside the case, so no beam can reach your eye in normal use. A pocket pointer, shining in the open, sits in a higher hazard class.

America's Airborne Laser, which shot down a test missile in flight in 2010, was built into which airliner?

Boeing 747: a jumbo freighter carried the megawatt-class chemical laser, which did destroy a missile in flight. Two years later the one-off aircraft flew to a desert storage yard and the programme was over.

Charles Townes built the first maser at Columbia University using which gas?

Ammonia: Townes and his students sent a stream of its energised molecules through a metal cavity, and coined the word 'maser' for the device that resulted.

Townes recalled that several eminent physicists insisted the maser could not work because it violated what?

Heisenberg's uncertainty principle: by Townes's account the doubters included Niels Bohr and John von Neumann. Von Neumann walked off, then came back about fifteen minutes later to tell him he was right.

The property that lets a laser beam stay narrow over great distances is called what?

Collimation: the rays leave the laser almost perfectly parallel, which is why a pointer's dot barely grows across a hall. Only diffraction, which no lens can remove, makes the beam spread at all.

What is the state called, needed in an ordinary laser, in which more atoms are excited than not?

Population inversion: left alone, atoms settle into their lowest energy state, so a laser has to be pumped with light or electricity to turn that usual order upside down.

Dennis Gabor invented which 3D imaging technique years before the laser finally made it practical?

Holography: Gabor devised it in the 1940s while trying to sharpen the electron microscope, but it needed a kind of light that did not yet exist. The laser supplied it, and his Nobel Prize followed in 1971.

Charles Kao shared the 2009 Nobel Prize in Physics for showing that laser signals could travel vast distances through fibres of what?

Glass: the fibres of the 1960s lost their signal within metres, and Kao showed the fault lay in impurities, not in glass itself. Made pure enough, it could carry light for 100 kilometres.

The 2023 Nobel Prize in Physics honoured laser pulses so brief that they are measured in which unit?

Attoseconds: there are as many in one second as there have been seconds since the universe began, quick enough to film electrons, whose movements were once thought impossible to follow.

Ronald Reagan's 1983 plan to destroy missiles with space-based lasers was quickly given which nickname by its critics?

Star Wars: critics chose the name because the space lasers the plan depended on had not been invented and were known only from the cinema.

The first laser was built in 1960 at a Malibu laboratory named after which aviation tycoon?

Howard Hughes: the laboratory was the research arm of the aerospace company he founded, which went on to build laser rangefinders that armies adopted.

Which NASA rover was the first to zap Martian rocks with a laser to find out what they are made of?

Curiosity: in August 2012 it hit a fist-sized rock named Coronation with 30 laser pulses in ten seconds, reading the rock's chemistry from the glow of the vaporised specks.

In laser tattoo removal, what does the beam do to the ink?

Shatters it into fragments: the pieces are small enough for the body's immune system to carry away, which is why a tattoo goes on fading for weeks after each session.

Laser-guided bombs were first used in combat during which war?

Vietnam War: the first ones were tried out in combat there. One aircraft held a laser spot on the target while another dropped the bomb that homed in on it.

Which highly tunable class of laser uses an organic gain medium dissolved in liquid?

Dye lasers: a single dye can glow across a wide band of colours, so the beam can be tuned smoothly from one colour to the next, something few other lasers manage.

Which kind of disc player reads its discs with a violet laser?

Blu-ray: the name comes from that blue-violet laser, whose shorter wavelength reads far smaller marks than a DVD's red beam, so much more fits on a disc of the same size.