Tribunes

Physics

Giorgio Volpe

Optics & Photonics Focus

A Solution Looking for a Problem

22 february 2010

This is a special year for all the people who have to deal with lasers daily –consciously or unconsciously. This year, 2010, is a yearlong celebration (Laserfest) of the 50^th anniversary of the invention of the laser.

Back in 1960, the first working laser was described as "a solution looking for a problem": a funny but useless experimental demonstration in physics. It was definitely an extreme case of lack of foresight. In all truthfulness, it was hard to predict at that time that lasers would go on to revolutionize not only research laboratories at the cutting edge of science, but also medical clinics and telephone networks – just to mention some applications. Lasers have taken over our everyday life: supermarket barcode readers, sliding doors, laser pointers… they all feature lasers!

American physicist Charles H. Townes is accredited as being the father of all lasers; in 1953, together with two graduate students, he created the first microwave amplifier, a device working similarly to still-to-come lasers but amplifying microwaves instead of light. Theodore H. Maiman then operated the first laser on May 16^th, 1960 while working at Hughes Research Laboratories in Malibu, California (USA) – currently owned by General Motors Corporation and Boeing.

What is a laser? In science jargon, a laser is a mechanism for emitting light via a process called stimulated emission, thus the acronym LASER or Light Amplification by Stimulated Emission of Radiation. Put simply, a standard laser comes about by placing an amplifying material between two mirrors, which form a cavity. Light then gets amplified while bouncing back and forth across the cavity and eventually emitted as a laser radiation.

Lasing has been achieved from so many materials and in so many conditions that we have lost count of how many lasers have been developed throughout their short but intense history: gas lasers, chemical lasers, solid-state-lasers, dye lasers, fiber-hosted lasers, semiconductor lasers, photonic crystal lasers, random lasers and so on so forth. This big family has been estimated to have more than fifteen thousand members, confident that some black sheep escaped the census. Of course not all of them are used in everyday life or even in research labs: most of them have fallen into oblivion!

A small amount of those fifteen thousand types though – around a few hundred probably – have revealed themselves to be extremely useful and found practical applications. A common laser used in industries can drill a hole through a very thick block of steel faster than the blink of an eye, with perfectly smooth edges every time. In addition, lasers also find applications in medicine, cosmetic skin treatment, data storage, and military defense. Take medicine as an example: lasers are used for bloodless surgery, eye treatment and dentistry.

This is just the tip of the iceberg: a lot has been discovered in laser physics but a lot has still to be discovered. Researchers keep on amazing us with new, fascinating and evocative ideas and experiments every day. Last August, for example, it was reported in the leading science magazine Nature the discovery of the smallest laser ever, as small as a virus. What is it useful for? It could perform on photons the same operations a transistor – the fundamental brick of nowadays electronic circuits – can perform on electrons, thus making computation with photons possible. Laser physics has already given a lot to science and redefined our standards in many aspects of our lives. Who can predict what is going to come next?

Tribune adapted from “The Smallest Laser Ever”

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