On the 60th anniversary of the first operation of a laser, let us reflect on the many advances lasers have enabled in various areas of physics.
The International Day of Light was designated by UNESCO to celebrate the role of light in science, culture and art, education, and sustainable development, and in fields as diverse as medicine, communications and energy. The date, 16 May, is the anniversary of the first successful operation of a laser achieved by Theodore Maiman in 1960, a result published in Nature entitled ‘Stimulated optical radiation in ruby’1. Maiman’s letter consists of two simple figures and fewer than 300 words, and — unlike many modern submissions — there is no concluding paragraph announcing the many scientific and technological advances the finding may lead to. The device itself (pictured) looks surprising in its simplicity. Sixty years on, as scientists and the general public alike have come to take lasers for granted in printers and pocket pointers, the key role played by the laser in scientific research is sometimes underappreciated.
Since 1960, numerous Nobel prizes in physics have been awarded for research done on or by lasers, spanning a wide range of research fields. Maiman himself was nominated twice, but although the recipient of many other accolades, he never received the Nobel. Charles Townes, whose work on masers Maiman refers to in his original paper, received the prize in 1964. Two years later, Alfred Kestler’s optical pumping technique was awarded another. Soon after, an abundance of new mechanisms for creating lasers were developed and lasers became a useful tool in research, medicine and industry over the latter half of the twentieth century.
In the past two decades, more Nobel prizes have been awarded for scientific techniques made possible by the use of a laser. For example, the optical frequency comb is a technique that uses ultra-fast lasers to make very accurate frequency measurements, which finds applications in areas such as metrology, spectroscopy and astronomy. Another laser-enabled technique is an optical tweezer that can be used to pick up and move microscopic particles; a laser beam attracts or repels particles owing to a change in refractive index between the particle and the surrounding medium. The ability to control matter on such a small scale has been adopted as an indispensable tool by physicists and biologists alike.
As the laser has evolved from an object of scientific study to a scientific instrument, it has also contributed to the discovery of new physical phenomena. Lasers have enabled the trapping and cooling of atoms to near absolute zero through techniques known as optical trapping and laser cooling. These techniques led to the experimental realization of new states of matter such as the Bose–Einstein condensate and the control of quantum states of atoms and molecules. Lasers also enabled the investigation of quantum mechanical phenomena such as entanglement and played an instrumental role in the detection of gravitational waves using laser interferometers (for an account of the latest developments in gravitational wave astronomy see the Feature article in this issue).
If Maiman had tried to speculate on all the possible applications of his work in his original letter, it is doubtful his imagination would have stretched so far. In today’s research landscape, physicists are continuously asked to justify the relevance of their work to practical applications and ground-breaking advances to secure funding. But the spin-offs from great discoveries are simply beyond anyone’s imagination. Maiman’s humble device changed the way we do scientific research and improved our everyday lives; we cannot predict which new ideas will have a similar impact.
Maiman, T. Stimulated optical radiation in ruby. Nature 187, 493–494 (1960).