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The long and winding road that brought lasers to life


Invention is less a straight superhighway and more a wandering path of twists and turns, writes Alan Finkel.


The first researchers to work on lasers had no idea just how pervasive their technology would become.
Luria Richard / Getty Images

It can seem like discoveries are made overnight. But those “overnight successes” usually conceal a saga of victories and setbacks played out by a large cast of characters over decades.

Take lasers. It would be hard to imagine modern life without them. They’re in the barcode scanner at the supermarket checkout, the surgery, your laser printer, driverless cars and guided missiles. Beyond these worldly uses, they’ve just allowed us to detect gravitational waves, giving us a new tool to probe the universe.

Lasers are also lucrative. Global annual sales run at about US$10 billion. But that’s a narrow valuation. Our internet is built on a freeway of optical fibres in which laser light efficiently zips data around the planet. The economic value of lasers would have to be counted in the trillions.

Lasers are everywhere, but few people realise the idea for this lynchpin of modern civilisation was conceived a century ago – by none other than Albert Einstein.

To retrace the path, we need to step back and explain how laser light differs from ordinary light. Sunlight bounces around in all directions with a range of energies – it’s like the choppy waves in a swimming pool full of splashing toddlers.

But get the toddlers out of the pool and turn on a wave generator. Now all the waves are moving in one direction with the same height and energy. That’s how laser light behaves. It's coherence – all that energy moving in the same direction – and the ability to focus to a fine point that makes the laser the most powerful and precise tool ever made.

The key to developing a laser was to realise that sometimes light could be emitted in discrete packets of energy.

Einstein came to this insight in 1905. In 1917, he theorised it should be possible to excite electrons so they all produce exactly the same size packets of light energy or photons. It was the foundational idea for the modern laser.

Over the next 40 years, other scientists added bits and pieces to that foundation, including those in the former Soviet Union and Bell labs.

In 1957, Gordon Gould, a Columbia University PhD student, put those bits and pieces together and described a method to stimulate electrons to produce light moving in synchrony with the same energy. He named it “Light Amplification by Stimulated Emission of Radiation”, or “laser” for short.

A few years later, Theodore Maiman at the Hughes Research Lab in California built the first practical laser by using a flashlight to excite electrons in the atoms of a ruby crystal. Each excited electron released a photon that went on to excite another electron. This triggered a chain reaction where all the photons of light had exactly the same energy, though bouncing around in all directions.

To capture only those moving in the same direction, he placed mirrors at either end of the ruby so only those photons moving parallel to the mirrors were reflected back and forth. It was these perfectly in-phase photons of equal energy that were captured at one end of the crystal as a laser beam of pure red light.

It wasn’t until 1977 that the first laser-based optic fibre communications system was installed, in Chicago. Music CDs debuted in 1982 with a Billy Joel album, and in 2009 the largest, highest‑energy laser in the world, known as the National Ignition Facility, was switched on to explore the possibility of controlled nuclear fusion. Today’s internet would be impossible without the extraordinary efficiency of lasers in optical fibres.

So the next time you log on, spare a thought for the epic journey that brought you laser technology.

It began with an ingenious idea, followed by a struggle to demonstrate that idea, failure, incorporation of new theories, more struggling, another idea, until finally the next genius in line turned the theoretical advance into an overnight marketplace success.

Transformational invention starts with fundamental science followed by ingenious technological development.

It takes time.

Alan finkel 2014b.png?ixlib=rails 2.1
Alan Finkel is an electrical engineer, neuroscientist and Chief Scientist of Australia.
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