The original "solution looking for a problem," the laser is now 50 years old. This gallery charts the evolution of a technology that underpins everything from the fibre-optic backbone of the internet to the search for clean fusion energy.
The first ever laser
The pulse that launched the laser age came from a fingertip-sized ruby rod nestled in the coils of a photographer's flash lamp. Theodore Maiman designed and built the little laser at Hughes Research Labs in Malibu, California.
Maiman showed that the blinding flash from the lamp could charge the ruby rod with energy that it then released in a pulse of pure red light in which all the waves marched coherently in phase, like soldiers in a lockstep parade.
Because the beam was powerful enough to drill holes in razor blades, physicists measured its power in gillettes, or the number of blades penetrated.
(Image: Kathleen Maiman)
The laser as weapon
As soon as the laser became real, military agencies and writers of fiction alike saw the comic-book ray gun made real and began to work on laser weapons. In 1964 arch-villain Auric Goldfinger threatened to saw James Bond in half with this "industrial" laser, at the time pure fantasy.
(Image: SNAP/Rex Features)
Holography was invented in 1948 to improve the resolution of the electron microscope, but Emmett Leith and Juris Upatnieks reinvented it using the laser in 1964 to make the first three-dimensional images viewable without special glasses.
They recorded holograms on photographic plates by splitting a laser beam, bouncing one beam off the object being imaged, then recombining the two beams to illuminate the plate.
After the plate is developed, illuminating it with a laser like that used to expose it projects a 3D image towards the viewer. This image of a toy train was one of the first they recorded at the University of Michigan's Willow Run Laboratory.
(Image: Juris Upatnieks)
The laser fantastic
To begin with, the laser palette was rather limited: helium-neon and ruby lasers emitted red light, and others produced invisible infrared. The first to emit the rest of the rainbow were ion lasers, made by passing a high-voltage discharge through argon or krypton.
Argon emitted blue and green light, krypton several other colours, and mixing the two gases made a laser that could emit across the visible spectrum. The laser light show was born.
(Image: Action Press/Rex Features)
The ubiquitous laser
Lasers became an everyday technology when US supermarkets decided to automate their checkouts using barcodes that could be read by a red helium-neon laser built into the counter.
Improved ways to make semiconductor diode lasers (shown here in comparison to a $5 bill) – which won Zhores Alferov and Herbert Kroemer the 2000 Nobel physics prize – has made lasers truly ubiquitous.
Chips like this are found everywhere from CD and Blu-ray players to red laser pointers and the backbone of the global telecommunications network.
The endless blade
In industry, lasers are the saws and drills that never get dull. The first lasers to earn a wage did so by machining very hard materials, such as diamonds, or very soft ones, for example baby-bottle teats.
Low-power lasers can cut and weld plastics; higher-power lasers can cut and weld metals. Early industrial lasers had to be big to be powerful, but new solid-state lasers are impressively small: today a length of thin optical fibre or a poker-chip-sized disc just a fraction of a millimetre thick can generate kilowatts, enough to slice a metal sheet a couple of centimetres thick.
(Image: Giuseppe Aresu/Bloomberg/Getty Images)
The laser as surgeon
The laser's first big successes in medicine came from performing operations inside the eye without cutting into the eyeball.
As early as 1962 a ruby laser welded a detached retina to a patient's eyeball to save their vision. A bigger success came in 1968 when surgeon Francis L'Esperance and Bell Labs engineers used argon-ion lasers to destroy abnormal blood vessels that would otherwise have spread across the retina and blind a person with diabetes. That treatment has now saved the vision of millions.
Today lasers are also used to carve tissue from the cornea to correct defective vision (as shown left), and bleach birthmarks and tattoos.
(Image: Stephen Jaffe/AFP/Getty Images)
The mother of all lasers
Controlled nuclear fusion has long been our best hope for clean energy generation, and in 1962 physicist John Nuckolls of the Lawrence Livermore National Laboratory in Livermore, California, proposed achieving it by using laser pulses to heat and compress chunks of heavy hydrogen isotopes.
Livermore has been pursuing the idea ever since with a succession of bigger and bigger lasers, culminating in the National Ignition Facility. It's a complex 192-beam system that last year generated a pulse with a megajoule of energy in a few billionths of a second, making it the most powerful laser ever built.
(Image: National Ignition Facility)
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