“I said, listen, we really have to look into semiconductors”

© Eric Jacobs

Harvard physics professor Eric Mazur reflects on the discovery of black silicon and the art of serendipity.

You originally wanted to be an artist, but now you’re a professor of physics. What went wrong?

I don’t think those two things are as far apart as they might seem! Scientists need to be creative, they need the ability to recognize and articulate patterns, just like artists. The act of interpreting a series of measurements has certain similarities to a painter steadily building up a scene. Take Leonardo da Vinci, for example: he was a great artist and a great scientist. Personally, I was inspired to pursue both of these areas by my family. My father was a professor of theoretical physics and my grandfather was an engineer. When I was little, they were always giving me science books and engineering kits. My mother was an art historian who taught me a lot about visual arts and graphic design. As a teenager, I really wanted to become a photographer or filmmaker. But in the end I chose science because it had always been my strongest subject at school. To be honest, the main reason was that I thought it would be easier to make a career in science than in the arts. But I still have my artistic side. I love photography and I invest great effort into crafting the perfect designs for the slides I use in my talks.

What are you working on at the moment?

So many different things. To give you one example, our group is currently investigating how light behaves when you send it through a material with a refractive index of zero. We’ve built what we call a metamaterial, a gold-clad transparent photoresist in which tiny crystalline silicon pillars are embedded. It turns out that light behaves very differently in this material than it does in ordinary materials. In our new material, photons essentially behave like electrons, giving us a far simpler and more efficient way of manipulating, bending and squeezing light at the nanoscale. That’s one of the projects we are working with at the moment. The overarching idea is to fabricate an optical chip that could process optical signals. Before we manufactured this zero-index material, we demonstrated that light, including ultrashort laser pulses, can be guided by “nanowires,” paving the way for nanophotonics in a broad frequency range. We are also expanding our research in the realm of biophotonics. For example, we developed an efficient way of using light to punch small holes in cell membranes that we can use to insert genetic material into the cell. And with an ultra-short pulsed laser, it only takes a second for us to perforate tens of thousands of living cells, potentially revolutionizing medicine and medical research.

The most interesting discoveries in my laboratory were all serendipitous.

You’ve already worked in so many different areas of optical research. How do you keep making all these discoveries?

I’ll tell you something: the most interesting discoveries in my laboratory were all serendipitous. None of these discoveries resulted from careful planning. Although …, at a Chinese restaurant I recently got one of those fortune cookies when the check came, and it said: “Good luck is the result of good planning,” and that actually got me thinking. Perhaps what really matters is giving luck a chance to run its course. People generally see research as something focused and linear, but trying things out and playing around are perhaps just as crucial. I’ve always encouraged trying out new things and pushing boundaries in my research group.

Prof. Eric Mazur pioneered in the use of ultra-short pulse lasers. He is a successful scientist and entrepreneur.

Prof. Eric Mazur pioneered in the use of ultra-short pulse lasers. He is a successful scientist and entrepreneur. Photo | Eric Jacobs

Could you give an example?

In 1997 my research group and I discovered black silicon, a form of silicon that is extremely good at absorbing light and is now finding applications in sensors and solar cells. At the time we were using femtosecond lasers to investigate how carbon monoxide reacts on platinum surfaces to form carbon dioxide, a reation that occurs in the catalytic converter of a car. This re search was funded by the U.S. government for two successive three-year periods, and when I submitted my third application for a new round of funding, I felt that I had better offer something else too — otherwise they might stop playing ball. So in my application I wrote, “We will also investigate other materials such as semiconductors.” This got a program manager excited enough to give me a call and ask for more details. As I had no specific ideas, I quickly made something up. The funding was extended for another three years and, as you might imagine, we continued our work on platinum. As the end of that third funding period approached, however, I suddenly got nervous because I had promised research on semiconductors. I called one of my students in the lab and said, “Listen, we really have to look into semiconductors now!” We unearthed some silicon wafers in the corner of the lab and my student found a cylinder of sulfur hexafluoride from our gas store as a reaction medium. He then fired femtosecond laser pulses at the surface of the silicon and it turned completely black, darker than black velvet. Black silicon was born. He called me, I came over and we examined the surface. That haphazard discovery ultimately led to a whole new field of research, a new company, and novel products.

You’ve followed quite a linear career path…

Not at all. I’ve zigzagged all over the place. When I was five years old, my grandfather gave me a book about the universe. I immediately knew that I would become an astronomer. So when I was 17 I began a degree in astronomy at Leiden University in the Netherlands. But after just six weeks I was totally disillusioned. Instead of investigating the big questions, all we were doing was working on formulae for calculating star positions. I wanted to see the forest, but all they kept showing me were the individual trees. I switched to physics, but as I quickly discovered, physics wasn’t any better than astronomy. Classes were really dull and mostly focused on endless problem-solving. I stuck with it because I was too embarrassed to switch fields again. But eventually something must have sparked your interest? In my third year, when I was just about ready to quit, I joined a research group and started to work in the laboratory. My project involved laser spectroscopy of cold gases, and I was really excited to be in the laboratory and have a chance to observe phenomena that nobody had ever seen before — uncovering new knowledge. Suddenly I was hooked.

I didn’t want to become an academic

Photo | Eric Jacobs

Photo | Eric Jacobs

Life: Eric Mazur was born in Amsterdam in 1954. He studied at Leiden University and moved to Harvard University in 1981 where he was tutored by the Nobel laureate in Physics Nicolaas Bloembergen.
Lasers: Mazur pioneered the use of ultra-short pulse lasers as a research tool. In 1989 he built a femtosecond laser at Harvard and became the first person to systematically investigate the effects of femtosecond laser pulses on materials. His research has led to numerous applications in both medicine and industry.
Career: Eric Mazur heads up the Mazur Group at Harvard which employs around 40 people. The team conducts research into areas including femtosecond laser microfabrication and nanosurgery, nonlinear nanophotonics, and pedagogical techniques in the realm of science.

And that made you want to be a professor?

No! I was determined to follow a career path that was different from that of my parents, I didn’t want to become an academic. So when I finished my doctoral thesis, I applied to Philips and was offered a job in their research laboratories. That was in 1981 when Philips was working on the development of the CD in a joint venture with Sony. I was assigned to a group that had to reduce the diameter of the discs from 30 centimeters to the 12-centimeter size we’re familiar with today. When I told my father about the job offer he said, “How about first spending a year in the US as a postdoc and learn more about optics?” I thought it was a great idea and Philips agreed to keep my job open for me. I wrote to Harvard and they accepted me as a postdoc. And what can I say? It’s been a long year, because I’m still at Harvard.

What made you change your mind?

I suddenly found myself in a place where 17-year-old string theory enthusiasts were chatting to 70-year-old   Sanskrit experts. Politicians, writers and artists were visiting the campus giving talks. And when I thought about Philips all I saw was that long, long corridor with an endless row of PhD nameplates stretching along the walls. All the offices were occupied by male physicists aged between 27 and 40 who spent all day long solving predefined problems. Suddenly it seemed so claustrophobic. So I became an academic after all. As you can tell, I make a habit of changing my mind.

You teach introductory courses for non-physicists. Isn’t that a bit unusual for a top researcher?

I love it! I think it’s so important to get people interested in science, and I think one way to do that is by changing the way we teach. I’ve already told you how boring I found most lectures when I was a student. When I started teaching, I realized I was doing exactly the same thing as my teachers had done to me. I may have been a good lecturer, but I was a terrible teacher. My students memorized facts and regurgitated them on the exam—much like I had done. This process bears no relation to knowledge discovery. So I developed a new active learning approach, now called the “flipped classroom”: students prepare before coming to class and the class period is more like a debate. I teach by asking questions. My students are constantly involved, and they learn more. My goal is to create “aha!” moments in the classroom. When I see that look of sudden understanding on a student’s face, I feel a great sense of satisfaction.

 

Eric Mazur about his method of Active Learning (2014)
Contact

Eric Mazur
E-Mail: mazur@seas.harvard.edu

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