Why Lasers Are Important Today

The laser has contributed to humanity as a powerful scientific tool for expanding human knowledge and in its many applications that help people directly. In the 40 years since Arthur L. Schawlow and Charles H. Townes published their technical paper on the principles of the laser in 1958, the device has been put to work in a vast range of applications and has assumed many forms.

Their paper caused an explosion of research by scientists at Bell Labs and at universities and industrial laboratories around the world that is unabated today at Bell Labs and elsewhere.

In communications, engineers recognized the potential of the laser to replace electrical transmission over copper wires, but how to transmit the pulses presented enormous problems. In 1960, Schawlow, D.F. Nelson, R.J. Collins and others transmitted pulses of light between Bell Labs facilities in Murray Hill, N.J., and Crawford Hill, N.J., a distance of 25 miles. Then called an optical maser, Townes' preferred name for the device, the laser produced an intense and extremely narrow beam of light that was more than a million times brighter than the sun.

Lasers in search of a medium

Unfortunately, laser beams could easily be adversely affected by atmospheric conditions, such as rain, fog, low clouds, and objects in the air, such a birds. Scientists and engineers suggested a number of novel schemes to protect the light from interference, including shielding it in metal tubes and using specially designed mirrors and thermal gas lenses to navigate around bends.

It took another major innovation, the development in the early 1970s of hair-thin strands of encased glass, called fiber optic waveguides, before the laser could transmit telephone signals. Since then, optical fiber has increasingly become the medium of choice for telecommunications companies to transmit voice, data, and video.

Telecommunications, once largely electronic, today relies on photons, as tiny semiconductor lasers routinely transmit light pulses carrying billions of bits of information per second over glass fibers. Wavelength division multiplexing technology uses various wavelengths, or colors, of light to transmit trillions of bits simultaneously over a single fiber.

The impact on medicine

The potential for lasers developed faster in the field of medicine after Kumar Patel of Bell Labs in 1964 invented the carbon dioxide laser, which soon permitted surgeons to perform highly intricate surgery using photons, rather than scalpels, to both operate on and cauterize wounds. Lasers today can be inserted inside the body, performing operations that a few years ago were almost impossible to perform, at little risk or discomfort to the patient. Shorter (green) lasers are being used to "weld" detached retinas, and Arthur Ashkin's work has been used to stretch protein molecules to measure their strength.

Schawlow often comments admirably on the contributions that laser technology has made to medicine, while noting with relief that no "death ray" lasers have been developed yet that could be used as instruments of war.

Lasers are everywhere today

Today, lasers are also used in a wide range of applications in medicine, manufacturing, the construction industry, surveying, consumer electronics, scientific instrumentation, and military systems. Literally billions of lasers are at work today. They range in size from tiny semiconductor devices no bigger than a grain of salt to high-power instruments as large as an average living room.

Still, whether they provide the energy that ignites a fusion reaction in isotopes of hydrogen, scan bar codes on produce in a supermarket, or provide the light source for Lucent Technologies high-capacity telecommunications systems, they all operate according to the basic principles put forth by Schawlow and Townes at Bell Labs forty years ago.

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