On 16 May 1960, Ted Maiman used silver coated mirrors, a ruby crystal and a photo flash gun to create the first working laser... Brian Culshaw, author of Introducing Photonics, 2020, explains what makes a laser so useful and introduces a number of the laser's vast applications.
The laser (Light Amplification by Stimulated Emission of
Radiation) can be thought of in the same way as any other oscillatory system; first
put together a means whereby something of interest can be amplified. This basic component will produce some noisy
version of the ‘something of interest’.
However, if we feed some of this ‘something of interest’ back to the
amplifying medium at a specific frequency then, with a little tuning to get
enough feedback, the whole thing will oscillate. We’ve all, without realising it, done this. Think
about pushing a youngster on a swing – exactly the same principles apply, but
now you’re the feedback, and the input energy!
The swing is the resonator – the ‘something of interest’ – and the
youngster provides the ‘noise’ by randomly pushing the ground with their feet….
In the laser case: end mirrors are the feedback and a host
of materials can provide the gain medium.
To create the first working laser, on 16 May 1960, Ted Maiman used
silver coated mirrors to provide the tuned feedback and ruby crystal to provide
the gain with a photo flash gun as the pump.
In December the same year the first gas laser – Helium Neon (He-Ne) –
appeared. This is often used still in
labs thanks to a safe power level and readily visible red light. Semiconductor lasers appeared in 1976. And the variations on the theme continue as
the applications for laser become all the more pervasive. In parallel these innovations have been
complemented by ever improving means of detecting light.
So what makes a laser so useful. Well, it makes light easy to focus down to a
very small spot, and so it can generate potentially very large optical power
densities. But – if you omit the lens –
the light can often go in a straight line over very large distances. Another more subtle aspect of this is that
the laser also produces light with a very stable optical wavelength which can,
with some ingenuity, be used to measure distances with amazingly high precision
(say around one millionth of the wavelength which is itself around one
millionth of a metre!).
So here’s just a few examples of how we’ve now come to rely
– often unknowingly – on the laser:
Here’s an obvious one: – the semiconductor laser
pointer – an extremely useful gadget
A semiconductor laser also reads your compact
discs, DVDs etc.… Now becoming less
commonplace thanks to…
The ever increasing capabilities of the internet
– but this in turn is thanks to the immense capacity of fibre communications
(laser driven) and huge semiconductor fabrication facilities essential to all
those data centres – relying on – you’ve
guessed it!– lasers to carve out the precision components needed.
In the housing industry, tradespeople, estate
agents and more measure room dimensions using a laser radar rather than a
ruler. It’s easier! And surveyors will use laser to define
straight lines.
Lasers are used extensively for welding and
cutting in high precision machining;
for engraving intricate patterns in ornamental
glass;
for surgical procedures (where there’s the incredible
bonus of automatic cauterisation) and in dentistry where the black of decaying
material absorbs more light than the good white tooth.
There’s also interest from tattoo removals, your
local optician and more…
Then there’s LIDAR – now making headlines for applications
in autonomous vehicles.
And shhhh… nuclear fusion, and laser weapons…
And the list goes on… It’s easy to find much, much more information on the web. There’s a recent (June 2019) issue of the trade magazine Photonics Spectra. And there are also numerous texts from the introductory to the specialist from Cambridge University Press, including …
And of course, my own, brand new, student resource: Introducing Photonics (Brian Culshaw, 2020).
To celebrate the 60th Anniversary of the Laser Cambridge are offering a 20% discount on the books listed above, and more. Discover your discount, interesting journal articles and more laser information at our Content Hub on Cambridge Core.
Brian Culshaw is an Emeritus Professor of Optoelectronics at University of Strathclyde, having previously served as the Head of Department and Vice Dean. He is also a Director of OptoSci Ltd, and was the 2007 President of the International Society for Optics and Photonics (SPIE)....
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