Techniques for creating synthetic diamond have been around for more than 50 years, but there are still relatively few players in the market. Fewer still target the photonics market, which is why Element Six is making a big name for itself in this sector.
The Element Six Group, itself part of the De Beers family of companies, comprises four business divisions: Advanced Materials, Oil and Gas, Hard Materials and Technologies. The first three are all concerned with the development of ‘supermaterials’ for abrasive use, while the last focuses on non-abrasive uses, with a strong emphasis on technology development.
The technologies division is specifically concerned with synthetic diamond manufactured using a microwave chemical vapour deposition (CVD) process, and a large part of this division is dedicated to the photonics market.
Adrian Wilson, head of the technologies division, based in Ascot (UK), says: ‘We’ve been producing synthetic diamonds using the CVD process for more than 25 years. As well as photonics, it has applications in semiconductors, acoustics, electrochemical water treatment, and quantum optics.’
Wilson describes photonics as the ‘fastest growing’ sector within its CVD business, and he puts the growth down to two factors: ‘Firstly, we have manufacturing scale – we are the world’s largest manufacturer of synthetic diamonds for non-abrasive use. What we’ve been able to do recently is produce synthetic diamond at a volume and at a price point that makes it extremely competitive. Secondly, there has been a drive towards higher power lasers, and existing materials, such as zinc selenide, are not appropriate for these higher-power applications in terms of lifetime and use. What we’re seeing is that typically above 8kW, synthetic diamond is coming into its own.’
Synthetic diamond can be used at several points along the photonics optical chain, but its main use is to provide an output window on a high power laser pump. ‘In extreme UV lithography, for example, the characteristics of synthetic diamond make it the perfect solution – low absorption, good heat dissipation and high resilience.’
Wilson says that synthetic diamond has three characteristics that make it particularly suited to use in optical applications: ‘Firstly, it has a very broad transmission spectrum – from deep EUV to infrared. It also has a high degree of thermal conductivity. Although it also has naturally low absorption, any energy that it does absorb can be dissipated very quickly. This helps ensure that the optic is not distorted by temperature. Lastly, it is a very inert material – both chemically and from a bio standpoint, and in addition it is highly scratch resistant. This inertness makes it suitable for use in extremely harsh environments.’
The synthetic diamond grown by Element Six has virtually all the properties of a natural diamond, but also several advantages from an industrial standpoint. ‘It’s very predictable in how it’s manufactured and what the end product looks like. By contrast, one of the attractions of natural diamond in the non-industrial world is that each diamond is unique. That’s not what you want in an industrial process. The synthetic diamond is extremely repeatable.
‘Also, given our experience in this area, we really understand what we need to do to the diamond in order to give it the properties required for the specific application. We can create variations that offer different levels of thermal performance, electrical conductivity, optical clarity and so on. We create different thicknesses and different diameters, or put different materials into the synthetic diamond that give it a different characteristic.’
Another key advantage, of course, is availability. ‘Large natural diamond is hard to come by and no two diamonds will be the same,’ says Wilson, ‘but with synthetic diamond, you can order 100 windows and they would all be consistent – and all be available.’
While CVD is a known process for creating synthetic diamond, the techniques used by Element Six are unique and have been developed from years of experience in production. ‘The recipes and the process we use, whether for mono-crystalline or poly-crystalline purposes, are all our own,’ says Wilson.
He also believes that synthetic diamond is not a competitor to incumbent technologies, such as zinc selenide. ‘We’re actually targeting those applications that require synthetic diamond, where those existing technologies simply will not do,’ he says. ‘We see synthetic diamond as an enabler for what the industry actually requires, particularly at the high power end. There will continue to be a market for zinc selenide, alongside that for synthetic diamond.’
Element Six works with leading names throughout the optics supply chain, and has more than 50 regular customers within photonics – and relationships with many of them stretch back more than a decade.
The company is growing its business in photonics all the time, capitalising on the industry-wide demand for higher power lasers. ‘To date, the majority of our business has been in Europe,’ says Wilson, ‘although with the opening of a new facility in California, we’ll be looking to drive growth in North America, and Asia in parallel with our staff in Japan.’
The rate of future growth, according to Wilson, will be determined ultimately by the range of end applications that will emerge in the months and years to come.
Wilson believes that it is the technical capability of Element Six that attracts customers to his company instead of his competitors. ‘We really understand synthetic diamond,’ he says. ‘We know how to optimise synthetic diamond for specific applications. It’s the assurance that customers have when they work with us that we really know what we’re doing. If we come across a new application, customers can be sure we have the technical capability to assess it and deliver a solution for it. We work closely with our customers to understand their requirements, and work with them on their roadmaps. We can develop synthetic diamond with the correct properties and at an appropriate price point for the applications we serve.’
Synthetic diamond is also being used in spectroscopy, where Element Six provides prisms and windows for spectroscopic systems. Applications here include pharmaceuticals, food and beverage and alternative energy, where the durability of synthetic diamond makes it particularly suited for use in diagnostic systems.
Another recent application is in Raman lasers, where Element Six is working with a university to develop a capability for yellow/orange lasers. ‘We’re providing the medium for the Raman laser,’ says Wilson. ‘We’re looking at novel resonator configurations, and we’re using a single crystal synthetic diamond for this application.’
In conclusion, Wilson says: ‘Synthetic diamond is at the point where it is very much a commercially available engineering material – it is no longer a blue sky product. Also, there are many applications in the optical market that are driving the need for diamond.’