New Caltech faculty member Alireza Marandi is on the cutting edge of laser science. Marandi, assistant professor of electrical engineering in the Division of Engineering and Applied Science, explores how nonlinear photonics, a field of optics, enables a broad range of previously less-explored opportunities for using lasers and light detectors for a variety of purposes, including molecular sensing and computing. Although lasers currently are used for a number of important applications from surgery to communications, imaging, and sensing, the devices are not always available at the wavelength needed for a given application. Marandi and others are exploring ways to convert laser wavelengths to suit any given purpose, by passing the light through specially engineered devices. Such nonlinear devices can also be used in information processing. Marandi received a bachelor's degree from the University of Tehran, a master's from the University of Victoria, and a doctorate from Stanford University. Recently, he answered a few questions about his life and work.
What brought you to Caltech?
Caltech has a great focus on science and engineering. Everyone you meet shares the same passion and drive, which fosters strong collaborations and motivates you to dig more deeply into your own field and be more effective. It has been a utopia for the type of research I am interested in.
Moreover, Caltech has played a critical role in the evolution of electrical engineering and photonics. Many of the prominent figures in the field have been at Caltech at some point in their careers as students, postdocs, or faculty members. It is extremely exciting for me to be a part of this community and contribute to its extraordinary impact.
What first got you excited about photonics?
When I was in primary school, I saw one of those sci-fi movies that had lasers in it. I don't even remember the name of the movie, but it got me interested in understanding what a laser was and how it was different from other light sources. Being a bookworm at the time, I actually went out and bought a laser textbook. Except for the first few pages, I could not understand anything in that book, but it helped me create an imaginary picture of the physics behind lasers. It was fun. Of course, everyone teased me for having a laser textbook in primary school.
Later, in high school, I got my hands on some laser diodes and built the simplest optical communication link. It was my first serious photonic experiment. When I got to college, I knew I would do electrical engineering. I had always been the type of kid that would try to build things. My parents may not agree with me on the term "build," but I "worked" with a lot of electronics in high school.
As an undergrad, I got a little off-track from photonics and found myself working a lot with artificial intelligence. I used artificial intelligence to design electromagnetic structures, which we built and tested. That got me back into learning more about electromagnetics and optics. Fast forward to after my PhD, when I ended up using photonic structures to solve some artificial intelligence problems. So, everything connects in a nonlinear way. In hindsight, one of the most appealing elements of photonics for me is that you can find a nice balance between science and engineering design and development.
Can you give an example of how nonlinear photonics can be used?
Think of breath analysis. There is a correlation between the molecular composition of your exhaled breath and what exists in the blood. So, there's a lot of useful information about your health contained in your breath, but it is difficult to analyze because the concentrations are so low. To overcome that, you could analyze the spectra of exhaled breath using lasers, searching for the spectral "fingerprints," or signatures, that reveal the presence of those compounds. The problem is that those fingerprints sometimes only show up at certain wavelengths of light, for which lasers and light detectors are not easily available. Wavelength conversion in nonlinear photonics enables accessing that information using the currently available lasers and detectors.
What are you most excited about in your field right now?
There are two application directions that I'm particularly excited about: one of them is related to information processing and the other is related to sensing, which I just described. For information processing, nonlinear photonics can provide access to extraordinary functionalities ranging from low-power logic operations to generation and manipulation of quantum states of light,but the challenge is that it's expensive and not easy to scale at the moment. The important question is how you can bring such functionalities, either for sensing or information processing, into a scalable platform to solve real-world problems.
Alireza Marandi
Credit: Caltech
