Ksenia Baryshnikova— Candidate of Physical and Mathematical Sciences, researcher at the International
Metalins and optical computer
- What developments are you currently doing at ITMO? Is this a scientific activity or work on projects?
— I am engaged in fundamental science, this is notinvolves an end result in the form of a product on the market. Yes, we have some test things - in particular, this summer I will go to work as a teacher at Sirius, and there we will make a metalens for Wi-Fi. We will make it up from balls, the size of the lens is about a meter. Quite a useless option for life. But the design that we will test is very useful in optics.
The metalens consists of a large number of plates orballs having a size on the order of the wavelength of light and distorting the direction and phase of the incident radiation. Arranging the plates in a certain order allows you to focus the light, simulating a regular lens. With the help of metalenses, it is possible to overcome the diffraction limit, that is, to resolve objects whose size is smaller than the wavelength of the light used.
Metamaterials- a composite material, the properties of which are determined not so much by the properties of its constituent elements, but by an artificially created periodic structure.
My main direction is dielectricnanophotonics. This is the area of nano-optics that studies the interaction of light with nanostructures made of dielectrics. Therefore, there is little absorption - and other physics than metals.
- Tell us about what Alexander Khanikaev does in ITMO. As I understand it, he and his colleagues created an artificial dielectric surface.
- Yes, and in it the spread of electromagneticwaves can be driven. I am a little involved in this area. You may know that the topic of topological insulators has recently become popular. This is a kind of material - a dielectric in the volume, but it can conduct an electric current on the surface. We have transferred this concept to photonics. This is light that does not spread in the material, but it spreads over the surface or through special interfaces on this surface, which we construct in a special way. Colleagues are doing it. I now also consider topological tasks together with Maxim Gorlatch.
- What are the areas of application for such dielectric surfaces?
— If we talk about topology, then it’s more likelylong-range applications in optical computers, when we need to control the path of a beam at the nanoscale, that is, send electromagnetic energy along some path. We must manage this process, switch it. But for now these are more theoretical ideas, and they are difficult to explain with real examples.
Optical computer- a hypothetical computing device in which calculations are performed using photons generated by lasers or diodes.
Most studies focus on replacingconventional (electronic) computer components into their optical equivalents. The result will be a new digital computer system for processing binary data. This approach makes it possible to develop technologies for commercial use in the short term, since optical components can be incorporated into standard computers, first creating hybrid systems and eventually all-photonic ones.
It’s much easier, for example, to talk about metalens, aboutwhich I already said. It finds application in modern devices that surround us. We have a pre-order for these metalenses from a company that wants to use them in ultra-thin smartphones, in cameras for them. Metal lenses provide very good resolution.
- How can metamaterials visualize diseased organs?
- To the question of medicine in our department fit withdifferent sides. There is a whole department, which is engaged in the improvement of MRI technology, so that the image contrast is higher, and you can not irradiate the whole body, but a specific area, so that the MRI time decreases. Now this is a very successful line of research, and our developments are beginning to be applied in hospitals.
Another area of research is plasmon.nanoparticles. They are used to identify and even treat cancer. They penetrate into the body, are absorbed in the area in which the tumor is located, and when we irradiate these nanoparticles, either some medicine is released there or local heating occurs, which allows treatment.
Photonic crystals, evolution and chameleon
— The theme of your speech at Science Bar Hopping is a chameleon. What does he have to do with it?
- Every time I return to Petersburg andI see these 50 shades of gray, I think about the jungle - everything is green, colorful, beautiful, birds of paradise are singing. And there is a chameleon, which both wants and changes color. And why can he do that, and we, the people, no? To find out, we need to remember everything we were told at school and the university, and answer the more basic question: where does the color come from?
- It is known that color comes from light.
- Yes, and the first thing that means - white color alreadycontains all the colors of the rainbow. Following the advice of Newton or the Pink Floyd group (laughs) and using simple instruments like a prism, we can spread white light into a spectrum. The wave, as is known, is characterized by a period - and the waves of different colors have different periods: the blue is slightly longer than that of the violet, and so on.
Pink Floyd Album Cover - The Dark Side of the Moon
Our eye is so arranged that it gives different signals.in the brain, when light arrives on the retina with a length of 600 nm or 400 nm, for example. In order for our retina to recognize color, we need not one photon or quantum of light, but a little more. At night, the light also falls on the retina, but we can only see the outlines of the objects. At night, as you know, all cats are gray. With a lack of intensity of radiation, we distinguish only where objects are lighter or darker.
When light falls on an object, its surfaceabsorbs something. For example, a cat may absorb blue. Then the orange-red will be reflected on our retina. Because blue and orange are complimentary. For example, chlorophyll is green because it absorbs red and blue light.
On the other hand, we have paints with which wewe can recolor objects. But this does not make it possible to change color the way a chameleon does - at its request. But what makes paints and pigments different in color? It is probably something that is at the molecular or atomic level. And as many molecules exist, there are as many transitions in them. This means that any minimal difference in energy levels leads to the fact that it can radically change its properties. If the excited level lags behind the ground level by exactly the energy of the incident photon, a “miracle” occurs and the molecule becomes colored.
Chameleon
You might think that a chameleon is green and red because there are corresponding pigments. And perhaps it changes colors because, for example, melanin is able to spread throughout the cells.
- But this is not true?
- Yes, it turns out that the chameleon has no green pigment at all, but there is only yellow where it is green and a little red.
- And how does he do it - change colors?
- Here we come to the most important thing.Light is not only a quantum, but also a wave. And here you need to understand what optical size an object must be in order for it to effectively interact with light as a wave. The object must be commensurate with the wavelength. This is where we come to the concepts of nanotechnology and nanostructures.
Here you can talk about the structural color, whichThere are three options. The first case is a multilayer reflector, a series of thin films superimposed on each other. For example, gasoline spilled on asphalt usually looks like rainbow spots due to interference, because the light is reflected not only from the outside, but also from the inside too. The second case is a diffraction grating, for example, a CD disk on which we observe diffraction orders and color variations. In order for the lattice to effectively interact with the light, its period must be a multiple of the light wave period. That is, there is a direct link between the parameters of the material and its color. The third case is a three-dimensional photonic crystal, for example, opal. But in fact, this is all one case - a photonic crystal, but depending on its dimension.
Photonic crystal- a solid-state structure with a periodically changing dielectric constant or inhomogeneity, the period of which is comparable to the wavelength of light.
For photonic crystals, as well as for ordinary ones, there are “forbidden zones”. That is, for some photon energies, light is reflected - a photon dielectric, and for others, on the contrary, a photon conductor.
In nature, nanostructures are often found - thisbutterflies, especially tropical peacocks, aphrodite (sea mouse), living on the seabed, monkey, plants, and finally a chameleon. Photonic crystals are under his skin. Depending on its state, the period of these crystals changes, and therefore the wavelength of the light with which they interact also varies. In the upper layer of the skin of a chameleon is located only yellow pigment. Then those same photonic crystals, in the normal state of the chameleon, reflect the blue color. The blue color of the photonic crystals in combination with the yellow pigment form the very green color of the chameleon. Interestingly, there is another layer under the layer of these photonic crystals - more separated. It is designed to reflect infrared light so that the chameleon does not overheat. In essence, nature in the process of evolution created ideally optimized structures, which so far, unfortunately, is inaccessible to humans in such perfection, although we are trying to copy this into nature.
“Why should I completely slaughter my personal life for the sake of science”
- At Science Bar Hopping surprisingly many invited female scientists. And what about the team at your faculty? Many girls are physicists?
- We have a lot of girls.And no one even thinks that there is some kind of gender problem or inequality. Everything is very good and positive. I have never encountered discrimination, if your question implied this particular detail.
- And when choosing a profession, parents or friends did not say: where did you go, physics, optics, horror?
- I have a family where my mother is an engineer, my father -PhD, grandmother - also an engineer. All women in the family taught, so for us it is more than normal. I was even a little forced to go this way. But all the same, when choosing a profession, there were many doubts.
I, for example, met with the opinion that peoplesciences must sacrifice their personal lives. And if a man supposedly can do it, then a woman is not. But I do not understand why I should completely forget about my personal life for the sake of science, and not just take my vocation as a job in which you can achieve success and outstanding results.
- Why does this stereotype still exist that career is the wrong choice for a woman?
- Well, what can I say?We have a patriarchal society. But if we talk about why we cannot move away from it so easily, then the problem lies in the attitude towards women. Women give birth to children, very often they are left alone, as a rule, there is no support, and young mothers are often not hired.
Therefore, parents tend to protect the girl,set it up: you have to be a good wife so you don’t end up in that situation. But of course, I am not ready to condemn all people with such attitudes. But it seems to me that state support should be bigger and stronger, especially for women who want to have children. I, for example, do not have a child yet, but I want to have children in the future, and I hope that because of this I will not have to leave science.
- What do you think about the fact that in some countries women are specifically supported in science, for example, with grants, even if they have not done anything outstanding? Is this a reverse discrimination?
- Of course have. And that's not very good.It is much more important at the stage of kindergarten, school, when a woman grows up, to pay more attention to the learning process, to what teachers do and say, so that already at this level the ideas of equality are absorbed.
When the woman has already grown - and then suddenlyit turns out that the world still treats a man and a woman differently - it causes contradictory feelings. This is strange and wrong. On the other hand, there is a scholarship for women scientists from L’Oreal. What's bad about it? I do not know, it seems to me, as a temporary measure of support for women in science, this is normal (it is a scholarship, not quotas), but someday this will not be necessary.