It’s a deceptively simple answer. Behind it lies a career spent learning how to grow and control materials at the atomic scale, and turning them into tiny devices that can generate and manipulate light in increasingly powerful ways.
Now, newly appointed professor, Semenova works at the intersection of materials science, photonics and quantum technology. Her research ranges from tiny lasers and optical connections on and between chips to quantum light sources designed to operate at the same wavelengths already used by today’s telecommunications networks.
Her approach is grounded in a belief she developed early in her career: that good materials are the foundation of everything, both for fundamental science and technologies that eventually find their way into everyday life.
The raisin inside a bread roll
Semenova began her research career in Russia, working in a laboratory focused on semiconductor materials and epitaxial growth – the process of building a crystal layer by layer on top of another crystal.
It was here that she learned the patience required to work with materials at this level.
Epitaxial growth may sound far removed from everyday technology, but its applications are remarkably familiar. The semiconductor lasers produced using these materials are now fundamental to long-distance telecommunications and the internet.
“That was basically what motivated my career,” Semenova says. Fundamental research driven by applications with real-life use.
After completing her PhD, she moved to France for a postdoc. There, she continued working with quantum dots and lasers, while becoming increasingly interested in quantum applications.
Quantum dots are tiny structures made by embedding one semiconductor material inside another. Semenova compares them to a raisin inside a bread roll: a tiny insertion of one material inside another, created with such precision that the entire structure remains a single crystal.
These tiny structures can have remarkable properties. They can be used to make lasers, but they can also act as efficient sources of individual particles of light – photons – which are important building blocks for quantum technologies.
During her time in France, Semenova developed an approach for synthesizing quantum dots that emit light at 1550 nanometres, the wavelength widely used in optical telecommunications.
That was significant because quantum light sources were often developed at shorter wavelengths, meaning that their light then has to be converted to the wavelengths used by existing telecom infrastructure.
Semenova wanted to do something different.
“I want to address the exact wavelengths we need for real-life applications,” she says.
From tiny dots to tiny lasers
At DTU, she has continued working with epitaxial growth, but has expanded the applications of the technology.
One strand of her research focuses on quantum dots for very small lasers. Rather than targeting the long-distance communications for which semiconductor lasers are already well established, the aim is increasingly to bring optical communication onto the chip.
Her work has already contributed to the development of nanolasers at DTU in which light is confined to extremely small volumes. At these dimensions, the surface of the device becomes increasingly important: surfaces that would normally be negligible can start to affect how well the device works.
Semenova therefore also studies how to preserve the quality of these surfaces – another example of how her work starts with the material itself.
Her research now touches several areas across DTU Electro, from nonlinear photonic devices and nanolasers to communication and quantum technologies.
Smaller, faster and more efficient
Looking further ahead, Semenova is cautious about predicting exactly what her field will look like decades from now. But she sees a clear direction: miniaturisation and integration.
“We can bring more complexity onto the chips and on the architectures we are building.”
Smaller devices mean more components can fit onto a chip. That means greater scalability and more functionality, while at the same time allowing researchers to increase bandwidth and reduce the energy needed to move information.
One particularly promising direction is electronic-photonic integration, where optical connections replace some of the electrical connections inside computing systems.
Light can carry enormous amounts of information, and using photons to move data can reduce the energy lost as heat compared with moving the same information electronically.
And as photonics increasingly intersects with quantum technology, the same technological advances could also contribute to more secure communication.
But Semenova is not convinced that the future necessarily belongs to the single, all-powerful quantum computer that currently dominates the public imagination.
She points instead to the technologies developed along the way, the ones, which will find a realisation and application in the real world no matter what happens with the quantum computer.
For Semenova, however, the precise form of the future is almost secondary.
The important thing is having the materials unlock new possibilities.
And that brings her career back to where it began: at the atomic scale, patiently growing one crystal layer at a time – and discovering what happens when the atoms do what she wants them to do.
