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John “JJ” Joannopoulos, the Francis Wright Davis Professor of Physics at MIT and leader of the MIT Institute for Soldier Nanotechnologies (ISN), passed away on August 17. He was 78.
Joannopoulos was a remarkably productive investigator in the realm of theoretical condensed-matter physics, and an early innovator in the examination and utilization of photonic crystals. Numerous breakthroughs from his work on how materials can be engineered to manipulate light have resulted in groundbreaking and life-saving technologies, ranging from chip-based optical waveguides to wireless energy transmission, health-monitoring fabrics, and precise light-activated surgical instruments.
His impressive career spanning over five decades was devoted entirely to MIT, where he was recognized not only for his significant scientific contributions but also for his generous and steadfast mentorship. He made a dedicated effort to maintain profound and impactful collaborations with many of his former mentees and postdoctoral researchers, many of whom have progressed to faculty roles at esteemed universities and to leadership positions in both the public and private domains. Throughout his fifty years at MIT, he forged enduring bonds across the campus, contributing to both scientific advancement and friendship.
“A scientific titan, inspiring leader, and exceptional communicator, John possessed a generous and kind heart,” says Yoel Fink PhD ’00, an MIT professor of materials science and engineering who was formerly a student of Joannopoulos and a long-term collaborator. “He had a remarkable ability to see the good in people, always keeping his mind and heart open. Asking little for himself, he devoted everything to the care of others. John led a life filled with significant impact and meaning — relishing the details of truth-seeking, achieving rare discoveries, and mentoring countless students to reach excellence. With warmth, humor, and relentless optimism, JJ left an unforgettable mark on science and on everyone fortunate enough to know him. Above all, he was a loving spouse, father, grandfather, friend, and mentor.”
“Ultimately, the most extraordinary aspect of him was his unparalleled humanity, his capability to make you feel as if you were the most valuable thing in the world deserving of his focus, regardless of who you were,” states Raul Radovitzky, ISN associate director and the Jerome C. Hunsaker Professor within MIT’s Department of Aeronautics and Astronautics. “The legacy he leaves extends beyond equations and innovations; it resides in the lives he influenced, the minds he invigorated, and the kindness he spread in every space he entered.”
“JJ was an exceptionally unique colleague: a brilliant theorist also skilled at pinpointing practical applications; a nurturing and motivating mentor to younger scientists; an exceptional educator who knew each student in his class by name,” states Deepto Chakrabarty ’88, the William A. M. Burden Professor in Astrophysics and head of MIT’s Department of Physics. “He will be profoundly missed.”
Layers of light
John Joannopoulos was born in 1947 in New York City, where his parents both immigrated from Greece. His father was a playwright, while his mother worked as a psychologist. From a young age, Joannopoulos recognized his aspiration to become a physicist — primarily because the subject posed his greatest challenges in school. In a recent conversation with MIT News, he eagerly recounted: “You might not believe this, but it’s true: I aspired to be a physics professor since I was in high school! I relished the thought of working with students and generating new ideas.”
He studied at the University of California at Berkeley, where he obtained a bachelor’s degree in 1968, followed by a PhD in 1974, both in physics. That same year, he joined the faculty at MIT, where he would dedicate over 50 years of his career — although at that time, the likelihood of securing a permanent position at the Institute appeared minimal, as Joannopoulos shared with MIT News.
“The chair of the physics department was the renowned nuclear physicist, Herman Feshbach, who informed me that the odds of attaining tenure were about 30 percent,” Joannopoulos reminisced. “But when you’re young and just starting out, that seemed much better than zero, so I felt, that was acceptable — there was optimism for the future.”
Upon commencing at MIT, Joannopoulos had a clear vision of his ambitions. He swiftly organized a group to explore theoretical condensed-matter physics, focusing specifically on ab initio physics, which denotes physics “from first principles.” In this foundational work, he aimed to establish theoretical models to forecast the electronic characteristics and structure of materials, based solely on the atomic numbers of the constituent atoms. Such fundamental models could be utilized to comprehend and design an extensive array of materials and structures.
Then, in the early 1990s, Joannopoulos pivoted his research direction, motivated by a paper from physicist Eli Yablonovitch at the University of California at Los Angeles, who conducted preliminary studies on materials capable of influencing the behavior of photons, the particles of light. Joannopoulos identified a link with his first-principles analyses of electrons. Together with his students, he employed that methodology to predict the fundamental behavior of photons in various categories of materials. His team was among the initial pioneers in the realm of photonic crystals, examining how materials can be manipulated at the nanoscale to govern the behavior of light traveling through them. In 1995, Joannopoulos co-authored the inaugural textbook on the subject.
In 1998, he challenged a long-held assumption regarding light reflection and dramatically revised it. This assumption suggested that light striking a structure composed of multiple refractive layers could reflect back, but only over a limited range of angles. However, Joannopoulos and his team demonstrated that the contrary held true: If the layers of the structure adhered to a specific design criterion, the entire structure could reflect light emanating from any and all angles. This structure became known as the “perfect mirror.”
This revelation propelled another insight: If the structure were formed into a tube, the resulting hollow fiber could function as a perfect optical conduit. Light traveling through this fiber would reflect and bounce around inside, without scattering away. Joannopoulos and his team harnessed this understanding to create the first precision “optical scalpel” — a fiber that can be safely manipulated while delivering a highly focused laser, precise and powerful enough to conduct intricate surgical operations. Joannopoulos assisted in commercializing this innovative tool with a startup, Omniguide, which has since supplied the optical scalpel to support hundreds of thousands of medical interventions worldwide.
Legendary mentor
In 2006, Joannopoulos assumed the role of director of MIT’s Institute for Soldier Nanotechnologies — a position he steadfastly maintained for nearly two decades. Throughout his committed tenure, he collaborated with ISN members across campus and in departments beyond his own, familiarizing himself with and supporting their endeavors. He facilitated numerous collaborations among MIT faculty, industry partners, and the U.S. Department of Defense. Noteworthy projects he supported included advancements in lightweight armor, hyperspectral imaging, energy-efficient batteries, and smart responsive fabrics.
Joannopoulos played a crucial role in translating numerous fundamental science insights into practical applications. He was a cofounder of six spinoff companies derived from his pioneering research, and assisted in establishing dozens of other firms that have advanced technologies ranging from laser surgical instruments to wireless electric power transmission, transparent display technologies, and optical computing. He secured 126 patents for his many findings and authored over 750 peer-reviewed articles.
In recognition of his extensive impact and contributions, Joannopoulos was elected to the National Academy of Sciences and the American Academy of…
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Arts and Sciences. He was also a member of both the American Physical Society and the American Association for the Advancement of Science. Throughout his career spanning over 50 years, he received numerous scientific accolades and distinctions, including the Max Born Award and the Aneesur Rahman Prize in Computational Physics. Joannopoulos was also a remarkable educator in the classroom, honored at MIT with the Buechner Teaching Prize in Physics and the Graduate Teaching Award in Science.
This year, Joannopoulos was awarded MIT’s Killian Achievement Award, which acknowledges the exceptional lifetime contributions of a faculty member at MIT. Beyond the numerous achievements Joannopoulos has attained in the realm of science, the award citation highlighted his enduring effect on the countless students he has guided:
“Professor Joannopoulos has acted as a legendary mentor to generations of students, motivating them to excel in science while simultaneously promoting tangible benefits to society through entrepreneurship,” the citation states. “Through all those he has influenced — not to mention their academic successors — Professor Joannopoulos has had a substantial impact on the advancement of science in recent decades.”
“JJ was an extraordinary scientist: He authored hundreds of articles that have been cited nearly 200,000 times. He was also a serial entrepreneur: Companies he co-founded garnered hundreds of millions of dollars and provided jobs for hundreds,” states MIT Professor Marin Soljacic ’96, a former postdoc under Joannopoulos who co-founded a startup, Witricity, with him. “He was an extraordinary mentor, a close companion, and like a scientific father to me. He always made time for me, at any hour of the day, and as much as I required.”
Indeed, Joannopoulos endeavored to genuinely assist his many students. In the classroom, he was “legendary,” says friend and colleague Patrick Lee ’66, PhD ’70, who remembers that Joannopoulos made it a point to memorize the names and faces of over 100 students on the first day, addressing them by their first names starting from the second day and continuing throughout the term.
Moreover, Joannopoulos encouraged graduate students and postdocs to pursue their ideas, even when they contradicted his own.
“John did not create clones,” states Lee, an MIT professor emeritus of physics. “He demonstrated how to conduct science by example, by showing care and sharing his optimism. I have never witnessed anyone so deeply cherished by their students.”
Even students who strayed from the path of photonics have maintained close ties with their mentor, as evidenced by former student and MIT professor Josh Winn ’94, SM ’94, PhD ’01.
“Although our collaboration ended more than 25 years ago, and I now work in a different area, I still feel like a part of the Joannopoulos academic family,” expresses Winn, who is now a professor of astrophysics at Princeton University. “It’s a devoted group with branches worldwide. We even organized our own series of conferences, initiated by former students, to celebrate John’s 50th, 60th, and 70th birthdays. Most professors would feel fortunate to have even one such ‘festschrift’ honoring their legacy.”
MIT professor of mathematics Steven Johnson ’95, PhD ’01, a former student and frequent collaborator, has personally experienced, and observed on numerous occasions, Joannopoulos’ generous and open-door mentorship.
“In every collaboration, I have consistently witnessed him casting a wide net to appreciate diverse perspectives, ensuring that everyone feels included and valued, and encouraging collaborations across groups, fields, and institutions,” Johnson remarks. “Kind, generous, and overflowing with contagious enthusiasm and positivity, he set an example many of his fortunate students have aspired to follow.”
Joannopoulos began his tenure at MIT around the same period as Marc Kastner, who had an office nearby on the second floor of Building 13.
“I would frequently hear loud debates accompanied by hearty laughter emerging from John’s office, where he and his students were discussing physics,” recalls Kastner, now the Donner Professor of Physics Emeritus at MIT. “I am certain this type of interaction contributed to him being an exceptional mentor.”
“He radiated such passion for science and goodwill towards others that he was simply delightful to be around,” adds friend and colleague Erich Ippen, MIT professor emeritus of physics.
“John was indeed a remarkable man — a truly exceptional one. Everyone who has ever collaborated with him understands this,” states Stanford University physics professor Robert Laughlin PhD ’79, one of Joannopoulos’ first graduate students, who later won the 1998 Nobel Prize in Physics. “He sprinkled a sort of transformative magic dust on people that inspired them to devote every waking moment to the pursuit of creating new and wonderful things. You can find traces of it in numerous significant places around the globe, all of which are better for it. There’s quite a collection of it in my office.”
Joannopoulos is survived by his spouse, Kyri Dunussi-Joannopoulos; their three daughters, Maria, Lena, and Alkisti; along with their families. Information regarding funeral and memorial services is forthcoming.
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