'Scientist's Code': Alexey Zhukov on First Quantum Dot Laser, Optoelectronics and Alferov's Luck
The admissions to bachelor's and master's programmes in Physics at HSE University-St Petersburg are still ongoing. Today 'Scientist's Code' introduces you to the head of the department to which these programmes belong. Please meet Alexey Zhukov, Corresponding Member of the Russian Academy of Sciences, Doctor of Physics and Mathematics and Head of the Department of Physics. We discussed with the researcher why it is important to switch to optical data transmission, where quantum cascade lasers are required and why Albert Einstein was a genius.
Research you are proud of
When I was finishing my studies, I happened to join the laboratory of Zhores Alferov which specialised in semiconductors. After graduation, I continued working there. In two to three years, my colleagues and I created the first quantum dot laser in the world—small semiconductor crystals. This invention became a truly world-class achievement, though we started it with pure enthusiasm.
I am still studying quantum dots lasers, now—in the International Laboratory of Quantum Optoelectronics. This topic is very up-to-date, including for the ecological sphere. Around 2% of the world’s energy usage falls now on data centres which process the information. This is a lot. It is necessary to reduce the consumption of electricity and switch to optical data processing. We can already transmit data over long distances—this is how the Internet works, however, it's not the same for short distances, so that the process would go inside a microcircuit chip. However, quantum dot lasers are likely to solve this task.
Now, we are focused on microdisk lasers. They are easy to produce, which means that they are easier to introduce in smartphones and computers universally—and of course, the price for customers won't change a lot. Besides, we study how to combine our devices with silicon—this is the material on which all modern electronics are based.
Obviously, I believe that our best researches are still ahead. In science, it often happens that one successful decision can close a topic for a long time or make it less relevant. Fortunately, it is not the same with optoelectronics and quantum dots: there are still a lot of articles published and active researches in lots of world scientific centres.
The discovery of quantum dots is recognised as significant all over the world. In 2023, three physicists, who have been working in St Petersburg for a long time, were awarded a Nobel Prize in chemistry for their researches related to quantum dots. We told about this in detail here.
Research which changed your conception of science
In science, a lot depends on chance and luck. Once, I heard a nice story about it from Zhores Alferov, Nobel laureate in physics. When Alferov studied semiconductor heterostructure for lasers, he needed materials with a similar crystal grid. And they found such—gallium arsenide and aluminium arsenide. In fact, it was common knowledge but aluminium arsenide was considered to be hopeless for study: this material decomposes in the air from water vapour. But one of the colleagues told Alferov: 'I have aluminium arsenide with the addition of gallium, and nothing has happened to it for a long time'. This is how Alferov realised that this would be a stable compound. If not for that case, the discovery might happen much later.
Together with other colleagues, Alexey Zhukov attended the award ceremony of the Nobel Peace Prize to Zhores Alferov. Read more bout how it went via the link.
Once, I was struck by quantum cascade lasers. The idea of them was offered back in the 70s by two physicists from Alferov's laboratory—Robert Suris and Rudolf Kazarinov. The assumption was far ahead of the technical capacity. The devices appeared 20 years later because, for them, it was necessary to synthesise semiconductors with high accuracy at very low thicknesses of layers and a great number of repeating periods.
The main difference of quantum cascade lasers is that they allow us to get a wave of almost any length. Such properties can be used for spectroscopic analysis in medicine, security systems to get images of hidden objects and so on. Such lasers have many applications, and there will be even more of them but for now, we need to stable their production.
Researcher you want to look up to
Many great scientists just like other creative people had a difficult character. I wouldn't like to look up to them in this aspect, I leave life principles aside. As for science, one can look up to many people.
I learnt a lot from Nikolay Ledentsov with whom we worked a lot on lasers. He is a remarkably goal-oriented person. I often heard from him: 'If you decide to do something, do it quickly or never at all'. It's not about doing it quick and dirty, no. You shouldn't put the work away for later because your rivals won't wait. One day, you wake up—and they have already published a similar idea. And you cannot do anything about it, only gnash your teeth.
I like scientists who manage to come up with something universal, related to many branches of science. For instance, once, lord Rayleigh entered the St Paul's Cathedral in London, stood under the dome and noticed that people standing on the opposite sides of the circle could hear each other almost perfectly. He named it the effect of the whispering gallery and found the explanation for it. It is a seemingly old discovery—it is more than one hundred years old. But later, it turned out that this discovery was relevant not only to acoustic waves but also to optic ones. In a round resonator, a wave reflects off the walls and runs almost without loss which will allow a laser to be very small.
The person who truly surprises me is Einstein. We don't know if he conducted any experiments but the speed with which he elaborated conclusions and came up with theories is beyond human understanding. It was Einstein who wrote the first significant works on stimulated emission: to explain Planck's law, he assumed that under the impact of a photon, an atom started to radiate and it led to the appearance of two identical photons. Stimulated emission is the basis for the laser work, so if not for Einstein, we wouldn't be discussing them.
The main thing for a scientist
Don't be scared of the routine. There's a lot of hard work behind any result. After all, sportsmen also spend a lot of time on exercises, and actors—backstage. The same is true in physics: scientists have to regularly think their ideas through and write them down.
An ability to sensibly assess your time is also a valuable quality. I think every scientist should come to terms with the fact that they won't be able to read all new articles on their topic. There are too many of them being published. In this case, I would recommend paying attention to thematic reviews and special editions of journals devoted to a certain question.
It is equally important to present honest results. You mustn't fit scientific facts into your hypotheses. If you are not sure about something or cannot explain it—write it just this way. Honesty is much better than an unreasonable guess. And remember: a negative result is also a result, you shouldn't be ashamed of it.
Sources of inspiration
My colleagues. I was always lucky with them wherever I worked. If I don't know how to do something, there will always be someone who will teach me. I have always tried to reach for people as communication with them gives me more ideas.
Of course, some people like working alone but I cannot do this. It seems to me that scientists, and researchers are the main values of any laboratory. Without people, any device is useless. If there is a device but no people, it is nothing. But if there is no device but a person, a device will appear somehow. People are more important than any machine or device.