# A day of light

15 May 2018
Taken from the May 2018 issue of Physics World

James McKenzie reflects on the business impact of lasers and light-emitting diodes

This month sees the first International Day of Light. Wednesday 16 May was chosen because it is the anniversary of the first successful operation of the laser, as demonstrated by the American engineer and physicist Ted Maiman in 1960.

It’s a good choice, because the laser is a perfect example of how a scientific discovery can yield revolutionary benefits to society in all sorts of areas, including communications, healthcare and manufacturing. However, when I read the words “first successful operation of the laser” on the International Day of Light website (lightday.org), I had to look further, as it sounded like there might be more to the story.

I have spent most of my career working in photonics, optical communications and lighting, so I was already somewhat familiar with the laser’s history. However, the details still interested me. It turns out that although Maiman did indeed demonstrate the first working laser on 16 May 1960, he is not the only person with a reasonable claim to have “invented” the laser. The other is Gordon Gould, another US physicist who described “Some rough calculations on the feasibility of a LASER: Light Amplification by Stimulated Emission of Radiation” in his lab notebook in November 1957.

## Laser blues

This was the first recorded use of the famous acronym, and Gould had the foresight to get his notebook notarized. However, he clearly had poor advice in other areas, because he didn’t patent his idea, incorrectly believing that he needed to demonstrate a working device first. In his defence, in the early days of the laser, people were aware it had proved a theory described by Einstein in 1917 but felt it was an invention looking for a job.

Gould was forced to endure a 30-year‑long legal battle before he was eventually awarded a string of laser-related patents and millions of dollars in back royalties. This is a key point in commercializing technology: future inventors should make sure they get the kind of patent advice Gould received later in his career, rather than at the start.

There is, of course, a lot more to light than just the laser. I don’t think anyone has ever really worked out the full impact of light on society, but here are a few numbers:

• The global lighting market (for lamps, street lights and so on) is worth about $120bn; • The global optical communications market, with the laser at its core, is worth about$15bn, and includes the network of optical fibre that underpins the high-speed Internet;
• Firms in the UK Photonics Leadership Group contribute almost £13bn to the British economy and employ 65,000 people, making it larger than the UK pharmaceutical industry.

None of these markets developed overnight. When I started in this field in 2007, for example, everyone was getting very excited about LED lighting and were predicting efficiencies of more than 200 lm/W (where the lumen (lm) is the unit of luminous flux per watt that determines the efficiency of a light source). People were also talking about incredible lifetimes of 50,000 to 100,000 operating hours. Both figures were seen as a great improvement on incandescent lamps, which last for 1000–3000 hours and have efficiencies of 10–20 lm/W.

However, the first products were expensive, even if they did mostly work as promised (if engineered properly). That meant that early on, LED lighting was sold on a “total cost of ownership” basis and was adopted in areas where the cost of maintenance was high, such as tunnels, high ceilings and other inaccessible places where it costs a lot to change a light bulb. Only now – a decade later – are LED lamps heading past the 200 lm/W mark and becoming as cheap as any other lighting.

How did this happen? Well, one reason is the US Department of Energy (DOE), which committed to an ambitious roadmap between 2000 and 2020 for developing better light-emitting diodes, phosphors, packaging and drive electronics. Additional impetus came from a near-global phased removal from the market of inefficient incandescent lighting led by the EU, US and Japan. The goal was to improve the efficiency of LEDs from around 20 lm/W to at least 200 lm/W while also cutting costs dramatically, from \$5 to pennies for one LED.

At the beginning, there was so much to do, but the goal was clear and a combination of funding, subsidies and visibility helped everyone get behind the plan. All the tricky technology issues were solved rapidly by a mix of academic research and commercial R&D. This progress got the attention of the global market. The Chinese government, in particular, saw an opportunity to make a big bet on LEDs, and as a result China has become one of the biggest manufacturer of LED devices, packages, lamps and lighting fixtures in the world.

## Promises fulfilled

From a global perspective, though, what is important is that we really did get all the energy savings we were promised, along with excellent lifetimes. LEDs and associated cheap “everlasting” lighting products are therefore expected to replace all other light-source technologies almost entirely within 10 years.

Of course, this poses a problem for lighting companies, as the business model – selling a fixture and providing replacement light bulbs for it – has not changed since the days of Edison. The lighting industry has tried to “fix” this before, in the late 1920s and 1930s, when the Phoebus cartel limited light bulb lifetimes to 1000 hours. Members of that cartel included several companies that still exist, including Osram, General Electric (GE) and Philips.

However, those days are behind the lighting industry now, and today’s focus is on innovations such as the digitization of lighting and “human-centric” lighting designed to mimic the Sun and make all of us sleep, function and feel better. That seems like a more noble approach than planned obsolescence, and it’s certainly something to celebrate – on 16 May or any other day.