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| G.V. Pavan Kumar (Photo Credit: Keerthi Raj B.S.) |
A landmark paper in Nano Letters, senior membership of the Optical Society (OSA), and DST’s Swarnajayanti Fellowship: the year 2018 turned out to be remarkable for Dr. G.V. Pavan Kumar. Working in the areas of plasmonics and nanophotonics, his research group is trying to understand how light interacts with nanostructures and molecules. In conversation with BS-MS student Rahul Iyer, Dr. Pavan Kumar talks about his fascination for light scattering and the perspectives he gained along the way through the two major influencers of his outlook—research and poetry.
On his research journey:
As I have developed from my PhD to this particular stage, it is my interest which has really guided me. I have had very long term interest in light and matter interactions, especially in terms of optics, and [related] everyday phenomena, and that has always made me look at things in slightly greater detail.
During my BSc days I had a very strong inclination towards optics in general. I had very good teachers who motivated me to look at optical phenomena in everyday life. Next, I went on to do an MSc in Physics, where I went in slightly greater detail and depth to understand atomic and molecular optical physics, which was my specialization. That really opened my eyes to some very interesting ways of looking into light-matter interactions.
My PhD research problem was to work on interfacing nanoplasmonic structures with some biomolecules, and this interaction was studied using Raman scattering, for which I had to know a bit of chemistry, a bit of biology and a lot of optics to do the experiments. So I had to learn about the way molecules behave when in the vicinity of, say, a nanostructure, and how these coupled structures behave when they interact with light; specifically, biomolecular Surface Enhanced Raman Scattering. It was a reasonably new concept with high relevance in optics way back around 2004, not only for the Indian community but also around the world, so the questions people were asking in the field were still in infancy. My advisor was very open-minded and gave me a lot of freedom to explore what I wanted to understand, and we got to do some interesting work then. I realized how people in various disciplines utilize concepts in Physics to successfully accomplish something within their own field, and how a training in Physics really helps [in such cases].
Having got this background, I then moved to Barcelona, probably one of the most beautiful cities I have lived in, for my Post Doc. I was there for a year at the Institute of Photonic Sciences, where I was looking at near-field optics, an advanced microscopy technique to look at light waves which are evanescent in nature. That really opened my eyes to high end optical effects, and also near-field optical effects as they are closely related to plasmonic effects, to understand the problem I was working on. Then I moved to Purdue University in US, where I switched to an interface between plasmonics and biology. In this project, we were introducing metallic nanoparticles in a biological cell to understand light scattering from those particles, so I had to learn about cell culture and nanoparticle interactions with biological membranes. You can see my trajectory has been such that I go and look at a slightly different problem, with one foot in the previous problem and the other in something totally new.
Then in 2010 I joined IISER Pune, with reasonable clarity of what I wanted to do: mainly some light scattering experiments on plasmonic structures, mostly Raman scattering: an inelastic kind of scattering which I had extensively studied this in my initial stages. We got started with a project on silver plasmonic nanowire, which included not only PhD students but also undergrads. We have vastly benefitted from this particular project, gaining reasonable attention in the community over the years. For example, one of the papers we published in 2018 was in Nano letters, which got quite a bit of attention, and work in this project is still carried out in my laboratory.
We have also been looking at light-matter interactions in nanoparticles, especially in fluids. In fact, of very high interest in my group now is a concept called ‘plasmofluidics’. Plasmonic structures in a fluid act very interestingly when they are excited by evanescent waves, and that is the interface we are really working at: nanophotonic phenomena and soft matter physics. We are trying to bridge these two, and trying to find common problems in these fields. It seems to be interesting, it is also relatively new, and part of my Swarnajayanti proposal was to look at this interaction. Hopefully, in the future we will go much deeper into this problem in both experimental and theoretical aspects in this area. Nowadays, I am looking at Mie scattering as well, which is an elastic scattering process, and also some nonlinear optical processes, and the light-matter interactions in nanostructures. Should we do it on a single nanostructure or a single fluid, is the kind of problem we are interested in. But the common theme has always been light scattering throughout my career, and will be for the foreseeable future. It is a fascinating subject, from the blue of the sky, to how the lighting in this room works, everything has to do with some scattering phenomena. Even quantum mechanics, for example, has a lot of scattering processes.
On research considerations and outlook:
Wherever I have been working on any kind of project, a kind of mantra of mine has been to look at whether it caters to my curiosity, and to see whether I would be able to achieve something which would also have a greater relevance, not necessarily in application, but also of some fundamental importance where a large body of researchers can be interested in such a problem. The questions that we have always tried to ask has always been to understand how one can reveal some interesting features of a nanostructure by light scattering. For example, a nanostructure made of gold fabricated in a particular way can act like an optical antenna, accomplishing large scale antenna effects like the directionality of light down to the nanometer scale. That has opened up the way light-matter interaction is now studied.
We are looking at such sort of antenna problems not only from top down approach in structuring using electron beam lithography and other such techniques, but also from bottom up approach by self-assembly. So we are seeing whether we can look at optical devices or components which can be self assembled from scratch, or trying to ask how light scattering can help us understand structures which have self assembled and the emergent phenomena which would not be otherwise envisaged. This has led me to look at how matter evolves as a function of initial conditions and time through light scattering.
Thus, the guiding principle has always been looking at simple phenomena in slightly greater detail, and utilizing some advanced optical/microscopy methods to understand these. Feasibility is also a factor when we do experiments, so the questions we are asking is guided by the structures we can actually produce.
On his research process:
I strongly believe in the principle that one should write a lot. It is very important to express your ideas in a concrete way, and writing helps shape your ideas, develop your point, look for loopholes in your argument, and so on. Everything evolves from writing. When I figure out there is some interesting question to be addressed, I write a hypothesis to be tested or a construction of an instrument, and after the experiment I bring the result back to paper to interpret, which guides my next step. The magic happens when you try to express the idea you’ll see either some parts of the ideas may not have evolved completely, or parts of the idea may be evolving in a direction it would not have if you were just sitting and thinking. Writing is essential and central to my research, whether for a grant or a paper, or just scribbling in your diary.
On teaching as a practising researcher:
I have written about this on my blog: in the process of trying to express, and trying to explain, you will also have to explore. I always feel that there is something very fascinating about trying to express an idea, no matter how uncooked it is. A teacher might have actually prepared something to teach an idea, but not everything has been pre-empted, so while teaching we might gain a new viewpoint of that idea. Teaching has a lot to feed into my research too. In research we are always looking for a problem and its connections to existing ideas, and teaching is a way of connecting things. Research also helps my teaching, because in research when putting across an idea to the community, it is important to address two questions: ‘Why is something interesting?’ and ‘Why is something important?’ Now if I can answer this, I can take a problem of contemporary interest even to a class of 1st years or 2nd years. They might not appreciate the whole question, but the mere statement of the problem would make the student aware of what is still to be addressed. This needs to be done in an undergraduate environment, because knowing the question is more important, and textbooks only have answers. It is also a fulfilling aspect of my work.
On basic science vs. applied research:
Pastuer’s quadrant, which is something I have been reading about for a while, is in some ways quite controversial. The Pasteur’s quadrant is considered the quadrant in which most of the universities should work on- if you actually work in the Pasteur’s quadrant, well and good- but thinking that working in this quadrant is enough is what is problematic to me. For me it is actually important to have the Bohr quadrant i.e. basic research, and also important to have the Edison’s quadrant, which is totally application oriented, and the choice of the quadrant is individualistic. But given that the funding is limited, there is a lot of debate nowadays about how research can be more beneficial to the society, but I think intellectual benefit should also be considered. So if one wants one could do targeted research with a goal in mind; for example, in climate change where the goal is to curtail temperature rise, so Edison’s or Pasteur’s quadrant is applicable. Let’s take another problem: there is a region of robotics called soft robotics, where people are using soft materials, say, to insert robots into a delicate environment or to squeeze them through a small channel. To address this problem, people are taking accomplishments from other fields, like polymer physics and chemistry for elastomers, fluid mechanics, etc. and none of these was done keeping robotics in mind. So the four quadrant system is an interesting way of looking at problem space, and it gives a model to look at and debate for funding agencies, but the quadrants categorise problems as black and white and there is a gray area between the quadrants, which needs to be appreciated. So it is best to approach problems purely on the basis of curiosity with an emphasis on human interaction. For example, recently I met chemical engineers attending a soft matter conference. I, as a physicist, sat in their talks and found connections that are interesting to me, but may not be directly relevant to an engineering problem, and vice versa. So the interfacing always happens when you see utility, not in application per se, but utility in terms of ideas.
On his affinity towards literature:
The seed of my interest in literature goes back to my undergraduate days. I studied in Bangalore University, which then had two languages as part of our course curriculum. I chose Sanskrit as first and English as second, so in between Physics, Mathematics and Electronics I used to have classes in Sanskrit where we were studying Swapna Vasavadutta or Raghuvamsham or Kalidasa’s plays, and in English Macbeth or Ulysses. It was during this time I kind of started appreciating poetry, because it has its own way of looking at things. At MES College of Arts, Commerce and Science, where I did my BSc, we had a very good college library which helped a lot. In my PhD days at JNCASR we had a student-run hostel library with a lot of interesting literature being part of the collection. I developed a very deep inclination towards Agatha Christie, and I still have probably all of her books. Virginia Woolf is another author I have very high regards towards. Of course, I also read Sherlock Holmes and other detective works, because these give a kind of intellectual kick. In my PhD days I was strongly encouraged by Sutirth Dey, my then senior, who put a spark in my mind, I remember having stimulating conversations about literature with him. Then during my Post Doc, I started writing a little bit of poetry in a blog called Astitva. I love poetry because the liberty of choosing the viewpoint adds a kind of new light on life itself, it gives you a universal way of looking at things. I like to make connections between what I write on my blog to beautiful verses, so I’ll start by quoting a verse and connect it to the concept I’m writing about. I really enjoy reading and writing.
- In conversation with Rahul Iyer
