Surya Shines her Laser on Relics
Posted On: 04-04-2017
WHO? Surya Harikrishnan, 36
WHAT? Researcher in archaeophotonics
WHERE? Manipal University, Udupi
Reported by Nandita Jayaraj
Last December, I conducted a science communication workshop at Manipal University as part of the Asia Student Photonics Conference 2016. Like any good hungry lab-hopper, I had one eye out for women scientists throughout the two days I was there. I didn’t have to look very far. Keeping a keen eye on the proceedings and offering the occasional instruction to the students was ‘Surya Ma’am’. While a lecture was in progress, I managed to find Surya Harikrishnan, assistant professor (senior scale) at the Department of Atomic and Molecular Physics and sit down with her for a chat about her life in science.
Thirty-six-year-old Surya has been a physics professor at Manipal University for over six years but has been teaching since she was fifteen. She is somewhat reluctant to call herself a researcher. “I officially registered for research only last year, and only from the year before that did I start my preliminary experiments,” she said.
The Whats and Whys of Photonics
Scientists have been studying light for centuries. As the dual nature of light came to be known (it can travel both as a wave or as packets of energy called photons), more and more optics, the study of light, came to become more and more application-oriented. Photonics is a newer term for the field of optics, though there is still an ambiguity surrounding the difference between the two terms. Some consider optics as the study of vision, making it a subset of photonics, the study of light; others regard photonics as applied optics. Because of these varied interpretations, it is not considered wrong to interchange the two words. From what I could gather at the conference, photonics was being considered in the broader sense – as the study of light.
When light hits an object, the two interact in interesting and unique ways. This interaction is typically a pattern of light and dark bands we refer to as a ‘spectrum’. The most popular spectrum is the rainbow, which is the result of white light interacting with water droplets or a prism. The pattern of the spectrum depends on the type, or wavelength, of the light that is used and the composition of the object that it hits. Because of this uniqueness, it is possible to identify the elements that make up an object based on the spectrum created by it when light (of a known wavelength) hits it. Instruments called spectrographs have been developed that can record spectra and compare it to a database to identify the elements.
An explosion of applications
As you can imagine, a technique that can tell you what something is made up of has an ocean of potential. Astronomers (like Seema, who we introduced you to last week) use spectroscopy to identify what far off galaxies, comets, etc. are made of; food-safety regulators use it to detect banned chemicals in food; there are even experiments going on in Surya’s department lab that look into medical applications of spectroscopy.
“Our lab has developed an oral cancer screening device that can detect cancer at early stages,” she informed me. “What we do is shine a laser into the oral cavity. The light emitted by the tissue is collected by a probe itself, and this is fed into a spectrograph.” Studies have shown that there is a marked difference between spectra of healthy persons, cancer-affected persons, and those prone to oral cancer – so, by comparing spectra, Manipal scientists have managed to show that it is possible to diagnose cancer early.
Hearing about the work in spectroscopy being done at the university, a group of archaeologists who were in nearby Mangalore for a meeting paid them a visit. They began brainstorming on how their expertises could be combined to answer some archaeological questions. Surya was tasked by the Head of Department to write a review article that would explore the scope of archaeophotonics. That’s when Surya’s interest in the topic began, so when she decided to register for a PhD, she knew what her research was going to be.
Throwing light on history
Photonics has so many applications – so why don’t we use it to study ancient pieces like archaeological specimens, she thought. “The first thing people ask is if we are doing dating (estimating the age of samples). No, this is not for dating. My study is based on pre-dated samples,” she said. “Say I get an ancient sample. I can study its elemental and structural composition using laser analysis.”
To do this, Surya uses a setup called laser-induced breakdown spectroscopy (LIBS), which was assembled by a scientist in their own lab. It consists of a neodymium laser that emits infrared light onto the sample that has to be analysed. When the laser hits the surface of the sample, explained Surya, tiny amounts of the sample turn into a charged state of matter called plasma. The plasma released is collected with a probe and transferred via optical fibres (fibres that can transmit light) into a spectrograph. The results are then compared with the NIST database, which has the standard spectrum for all the elements in the periodic table.”We know at what wavelengths zinc or copper, for example, are at, and so we can see whether something is present or not, and if so how much of it is present.”
Surya pictured some scenarios in which this kind of analyses would potentially be useful:
Scenario 1: Is this painting authentic?
Somebody is claiming that a painting is from the 16th century. Surya could do an analysis and find out which pigments are giving colours to the paintings. She can then run these against a database of known pigments listed according to how long they have been in use. If she spots a pigment in the allegedly 16th-century painting that started being synthesised only in the 19th century, then this means the painting may not be authentic.
Scenario 2: How can we save this painting?
Suppose the painting has turned out to be real after all. Now, the museum is going to want to restore it and keep it in good condition. If Surya can tell them what the material and the paint is made up of, it will help to decide what the best preservation method is.
Scenario 3: What can this coin tell us about the times?
Coins are made up of metals like copper. Metals are typically not found in their pure form but as ores. The process of extracting the metal from the ore, metallurgy, is becoming more efficient with time. If Surya is given a copper coin from the 16th century, she can analyse its level of purity and compare this with coins found in the same area at different times or different areas at the same time. This can be used to trace and compare technical expertise that existed in the world those days. Moreover, if a copper coin is found in an area whose soil does not have a lot of copper, she could deduce that the area had trade relations with another area richer in copper.
Of course, having just embarked upon her research career, Surya is some way off before these kinds of projects start coming to her. For now, she uses samples she sources from a colleague in the Department of Architecture who studies the palaeolithic era and from the Udupi Heritage Museum.
Don’t scratch my sample!
It’s not as if there are no other ways to determine what a sample is made of, but most of the traditional methods are not suitable for archaeological studies. “Archaeologists can’t subject their specimens to any kind of destructive techniques. Many of the older techniques involve crushing and powdering, but this means they will lose the sample,” she informed. Laser techniques like the one Surya uses, on the other hand, are relatively non-destructive. “Whatever form or shape or size your sample is, I do not subject it to any sampling process.”
However, the plasma formation means that LIBS involves tiny amounts of abrasion. “We might lose nanograms of the sample,” she conceded. “It depends on how precious your sample is. In pottery, a small bit is not important if we have one huge chunk. But I read of one case where they wanted to analyse an ancient script which was already in pieces. Moreover, it was important not to lose the pigment that was used to write on it. Here they could not afford to lose even a nanogram of the sample. In these cases, even LIBS is not recommended.”
Nevertheless, LIBS remains hugely attractive for elemental analysis due to its versatility, affirmed Surya. “It is instantaneous, spans a whole range of wavelengths and the same setup is sufficient for different elements; no specific setup is needed for different elements.”
Still some way to go
Surya recalled how an archaeologist once gave her three or four pieces of pottery that he had found lying 200 metres apart in a site in Karnataka. The pieces looked similar, so he wanted to understand if the pieces could be from the same pot. But Surya’s analysis showed that all three pieces had different spectra. The constituent elements were the same – they usually are, she said, in pottery – but the pots were probably fired in a furnace using different techniques or for different durations.
In spite of the results, Surya reminds me that results of archaeophotonic techniques cannot yet be used as conclusive evidence. “If someone says this is real, I can do an analysis and say that it needn’t be; I cannot say it is not. For example (in the pottery case), it could be that the different spectra was not due to ageing, but because one piece was exposed to more sunlight while the other was buried…”
LIBS still has some hurdles to cross before archaeophotonics can become more mainstream. The assembly, for instance, is still not always portable, making it unrealistic for some kinds of archaeological studies like cave paintings. “For now, my PhD objective is to study the applicability of these techniques for archaeology. Maybe in the next 10 to 15 years, we will become established and I can say ‘I will do analysis for you.’”
An itch to educate
Surya was born in Bombay and brought up in Calicut in Kerala. Even though she did her Masters in physics, it was always clear to Surya that teaching was what she wanted to do. “In school, I used to write on the whitewashed walls of her home with chalk thinking that it would never be seen, but later realised that it was visible at an angle! My way of studying itself was by imagining that I was a teacher,” she reminisced.
It wasn’t just an idle dream either. She began taking tuition classes as soon as she passed class 10: “I can proudly say that I’ve been earning since I was 15. In class 11 and 12, I would return from classes by four o’clock, take tuitions for younger students till seven o’clock, and then I would start my own studies. This is how it was till I finished my BSc.”
Surya took a break from teaching during her MSc but not for long. While pursuing a BEd degree (Bachelors in Education), she taught engineering aspirants part-time at a coaching institute. Wasn’t it too much? No, insisted Surya. In fact, it was the opposite. “BEd was very very stressful, but teaching, it was my relief.”
A turning point and a late decision
After her BEd, Surya taught for five years at Providence Women’s College in Calicut. Her decision to apply for the Indian Institute of Science’s Summer Research Fellowship programme is what she considers her turning point. She qualified and did a project at Centre for Excellence in Basic Sciences (CBS), Mumbai, under Deepak Mathur, who would become a mentor of sorts. Mathur advised her to continue at CBS. “I was about 28 or 29 then, and my job in Calicut was not a permanent one so I thought I should not miss this opportunity.”
Surya’s job at CBS was to set up the projects and the labs for the fourth-year students studying there. “I really enjoyed it because it gave me the opportunity to work with students who are the cream of the country and meet many senior scientists.” It was again Mathur who pointed her to an opening at Manipal University. She has been teaching here for six years now.
Though her position was a teaching one, Surya has always thought of research as something that will improve teaching. But the decision to start a PhD finally came only years later when she observed that most institutions these days looked for staff with PhDs. “You are kind of graded and judged according to your research because the number of publications is something you can quantify,” she noted. Luckily for her, she found herself in a place conducive enough to research for her to shed her initial disinclination for a long drawn-out research career. “In any other place, with my lack of motivation, I would never do it, but now I am in an environment that is always telling me to do research and there is a great lab,” she said.
Surya has a lot of things to look forward to in the coming years. Her PhD, of course, and also a book on archaeophotonics that she has almost completed. Meanwhile, her first love continues to be teaching. “Some people say ‘oh you are a physics teacher, you must love physics’. My answer is yes, I am a teacher, but because I love teaching,” she said with a smile.