Dr Wladislaw Michailow is a Junior Research Fellow in Physics. He explains his passion for the subject and why Terahertz science and technology fascinates him.
Why did you choose to study physics?
As a child I enjoyed experimenting at home with chemistry, physics, and electronics. I liked to take apart old and broken electronic appliances and to study their inner life. During my school years I created batteries from salt water and pencil lead and generated arcs from high voltage transformers used in old TVs to drive the cathode ray tube.
Later I transformed a cassette player into an external loudspeaker box, built a stereo microphone amplifier, and modified a cassette player to record audio on cassette tapes by making a custom electronic circuit to drive its tape head. To this day, I still like repairing, modifying, or upgrading electronics.
I decided to study experimental physics as it involves fascinating fundamental, challenging engineering, and exciting applied aspects. Instead of the simple experiments of my childhood, I am glad that now I can work on cutting-edge research topics and try to answer questions of modern science, using state-of-the-art laboratory equipment.
My electronics hobby also helps me now in the lab. This way I learn how certain engineering solutions are realised, and it also aids with thinking out of the box when attempting to solve experimental challenges.
Where did you study before Cambridge?
I did my BSc in Physics at the University of Augsburg in Germany, during which I explored surface acoustic waves, which are high frequency sound waves on the surfaces of crystals, and learned the basics of radio-frequency electronics. After that I went to the Walter Schottky Institute at the Technical University of Munich, where I studied Applied and Engineering Physics.
Tell us about your research
Terahertz science and technology is my research area. Terahertz (THz) waves constitute radiation with frequencies around 1012Hz, that is between the microwave and infrared regions. This is a frequency region that we struggle to make use of so far.
Nowadays, almost every modern electronic device uses electromagnetic waves, which differ in their frequency. For example, we listen to the radio at radio frequencies, communicate using mobile phones that transmit microwave radiation, can see in the dark using heat and night vision devices operating at infrared frequencies, take photos with cameras in the visible range, and use X-ray radiation to see into the human body.
The technology around the terahertz frequency range is not yet sufficiently developed for widespread everyday use. But THz waves could have numerous technological applications: in medicine, THz radiation is capable of visualising cancerous tissue (and unlike X-rays it is not harmful); in pharmacy, THz waves enable the chemical analysis of medicines, even within closed capsules; and in security, a THz camera could see through people’s clothes to discover hidden weapons or illegal drugs.
And as THz frequencies are higher than microwave frequencies, they could lead to ultrafast data communication that is even faster than current 5G wireless networks. In principle, instead of 10-100 gigabits per second data rates, we could go to up to 1 Terabit/s – that’s 1000 Gbits/s – or more.
This sounds incredible, what’s the problem?
The problem is that we don’t have sources and detectors operating in this range that would be efficient, cheap, and easy to use. Up to the microwave region, we use transistors – the electronic switches which form the basis of all modern electronics. But when moving to the even higher THz frequencies, their speed hits fundamental limitations that are difficult to overcome. On the other hand, THz waves are just too low in frequency to achieve optical transitions in a material, which is how digital cameras work.
Hence, we need to explore ways to work around these issues and find other approaches in order to exploit the full potential of the THz range. My research focuses on how THz radiation interacts with small semiconductor structures on the nanoscale, what quantum phenomena play a role there, and how this can be exploited to efficiently detect THz radiation or to realise quantum communications in the THz range.
A key part of my PhD research was studying how a two-dimensional electron system responds to THz radiation. My experiments allowed me to find a new quantum mechanism which gives rise to a strong response of such two-dimensional systems to THz radiation. So when a THz beam hits a device with such a system, you measure a large current or voltage across the device. This gives us a sensitive instrument that makes it possible to “see”, or to detect, THz waves.
What do you actually do in the lab?
I design, fabricate and measure semiconductor devices that are specifically tailored to detect or interact with THz radiation. Once the design is completed, the chips need to be fabricated. In the Semiconductor Physics Group at the Cavendish Laboratory, put simply we blow very clean semiconductor dust (single atoms) onto the substrate or wafer thus creating a ‘cake’ of different layers. The wafer acts like a plate on top of which you do the ‘baking.’
From these wafers, I cleave off samples and process them in our cleanroom. This work gives us packaged, functioning semiconductor devices that are ready to be embedded into electronic circuits. Most chips that I fabricate are THz detectors.
The measurements are carried out in a high vacuum and at very low temperatures of about -268°C, which is necessary for the THz laser source and detector to work efficiently. To do this, you mount the sample in a cryostat, an instrument that is used to achieve very low temperatures, and pump the air out. Then you cool it by pumping liquid helium from a large Dewar vessel through the cryostat. Because the samples that I study are light sensitive, I do most of the work in a dark lab with blinking LEDs from various instruments connected to a computer which controls the measurement and data acquisition.
How do you spend your time away from the lab?
Apart from electronics, my hobby is playing piano. During my school years I used to participate in piano concerts and contests. Now, I just play piano for my enjoyment, which I can thankfully do in the Trinity music rooms. I also like listening to classical music, mostly piano and organ music, and have enjoyed a number of concerts in the Trinity College Chapel.
What are you looking forward to most about your Junior Research Fellowship?
I am very grateful to have the opportunity to stay at Trinity after my PhD. I have enjoyed being part of the Trinity community since I came to Cambridge, and I am excited to join now as a Junior Research Fellow.
During my Fellowship, I would like to extend my horizons and look at my research from a broader perspective. The wide variety of research carried out in Cambridge as well as the rich scientific and social environment of our College presents the ideal opportunity for this. Having gained experience working with semiconductors in the technologically most important frequency ranges during my studies, I am also intrigued by the idea of extending my expertise to other areas of physics, such as biophysics, in the long term.
Find out more about Wladislaw Michailow.