One of the most important artificial materials, lithium niobate, has re-emerged as Australian researchers harness its properties for applications from space navigation to farming.
The material was first discovered in 1949. While it has been used in photonics components for decades, its true potential as photonics’ answer to silicon is only just being realised.
Lead researchers in advancing LN photonic chips are the University of Adelaide’s Dr Andy Boes and RMIT University’s Distinguished Professor Arnan Mitchell.
“Lithium niobate was first discovered quite a while ago, but recently it was possible to get wafers of very high quality, which makes it very attractive for semiconductor industry,” Boes tells Cosmos. “What is particularly interesting about lithium niobate is that it has very interesting material properties that can change the colour of light very efficiently and manipulate the light.”
The advantages don’t stop there according to Mitchell. The material promises to revolutionise photonics in the same way that silicon did in electronics.
“Lithium niobate covers a much broader range of the spectrum than silicon,” Mitchell says in an interview with Cosmos. “It’s transparent to visible light, but it’s also transparent into the mid infrared. It can also interact better in converting electronic signals into optical signals. Silicon can do a lot, but it can’t do everything. For example, you can’t see through it, so if you need to work with visible light, silicon can’t do it for you.”
Mitchell believes a shift toward LN could yield great advances in photonics.
“Silicon is what powers our laptops and smartphones,” Mitchell explains. “A lot of technology has emerged around silicon. The electronics community has been all about silicon. The photonics community has also been following silicon assuming that we need to use the same platform.”
“The advancement that’s happened recently is that you can treat lithium niobate, to some extent, the same way you treat silicon. So, you can start imagining using the same sort of technology that’s been used to make integrated circuits in silicon for making integrated circuits on lithium niobate,” Mitchell adds.
But let’s take a step back. What is photonics?
“In electronics one has electrons that go down a wire, for example, or in a semiconductor,” explains Boes. “Circuits can be switched on and off – manipulated into ones and zeroes. In photonics, it’s quite similar, just that, instead of having electrons, one has light particles called photons.”
Lithium niobate wafers hold promise for being transformed into integrated photonics chips, like the integrated circuits made from silicon semiconductors that form the bulk of modern computing.
“In photonics, you need all sorts of weird and wonderful components to actually make a circuit,” Mitchell says. “We’re trying to make as complete a toolbox of components as possible that you can print onto these lithium niobate chips.”
The researchers say that a key part of their research has been their ties with industry partners.
“What we are looking is partially application driven,” Boes says. “Industry partners came to us saying they would like particular functionalities so that our system operates more sensitively. For example they may want to detect minute rotations for navigating cars or drones. They came to us with these problems and said wanted a photonic circuit that for these applications.”
Companies look for solutions which, Boes says, are the “most efficient and treat the optical waves well so that they don’t get scrambled. Which material is actually most suitable for achieving that? Lithium niobate is one of the standout materials.”
Mitchell believes it is particularly important to promote Australian innovation in the development of LN technologies.
“Industry assumes that integrated circuits are inaccessible technologies that develop overseas somewhere in a giant multibillion dollar factory. What we’re exploring with lithium niobate is the ability to make chips perhaps a little easier than it is to make silicon chips. It’s also more flexible – you can do a lot more with it. So, you can engage with industries that have niche requirements or unusual needs, and possibly high value, modest volume, manufacturing requirements,” Mitchell says.
“I think that trajectory is important for Australia, because in Australia if you’re an industry, you’re not going to start making millions of components, you’re going to start with a few niche components and then grow.
“I’m very enthusiastic and dedicated to working with industry so that there is actually a credible manufacturing capability for these chips preferably in Australia, but particularly accessible to Australian industry.”
Both Boes and Mitchell are excited to see where the technology develops.
“I remember getting really excited by emerging computers when I was a child. And I see that same level of excitement now with photonics. All these new opportunities are opening up for all sorts of different applications that, in principle, have been possible but were just too difficult to realise practically.
“We’ve got a lot of money and time to do a lot of fun science and exploration. But I feel the responsibility to also make sure that this practical manufacturing is keeping pace with that,” says Mitchell.
“Since this technology is relatively young, I can see lots of opportunities for many applications in the future. As the platform matures, more and more advanced systems become possible. The complexity of these systems increases as light sources or detectors get integrated into the circuit like a CPU all integrated into one semiconductor chip. One can imagine that fingernail-sized chips can be integrated in consumer electronics like mobile phones,” adds Boes.