From the Special Topic of
According to our Special Topics analysis on photonic
crystals, the scientist whose work ranks at #9 is Professor
Shanhui Fan, with 52 qualifying papers cited a total of
1,747 times. In
Science IndicatorsSM from
Reuters, his record includes 222 papers, the majority
of which are classified in the field of Physics, cited a
total of 3,763 times between January 1, 1998 and August 31,
Professor Fan is an Associate Professor of Electrical Engineering at
Stanford University, where he heads up his own research group.
In the interview
below, ScienceWatch.com talks
with him about his highly cited work.
Please tell us a little about your research
and educational background.
I was an undergraduate student in Physics in the University of Science and
Technology of China, at Hefei, China, from 1988-1992. I obtained my Ph.D.
on Theoretical Condensed Matter Physics from the Massachusetts Institute of
Technology (MIT) in 1997. I was a Postdoctoral Research Associate and later
a Research Scientist at MIT for several years until I joined the faculty of
Stanford University in 2001. I am now an Associate Professor of Electrical
Engineering at Stanford.
What first interested you in photonic
"These days you can find
applications of photonic crystals in
practical every aspect of optical
After I got into MIT, I needed to find someone to work with. Professor John
Joannopoulos was very kind to take me into his group. He wanted a student
to work on photonic crystals, so I started. At the time the field was only
a few years old. As a young graduate student, it took me a while to
gradually realize, and this really was Prof. Joannopoulos’s vision,
that the idea of photonic crystals is very powerful, and can have
substantial impacts on practically every aspect's of optical technology.
Looking back, I am amazed that there are so many things that excite me in
this area even after working in it for fifteen years.
A key paper in your publications is the 1998
Phys. Rev. Lett. paper, "Channel drop tunneling through
localized states," (80: 960, 1998)." Would you talk about the
significance of this paper for photonic crystals?
This paper dealt with the optimal condition for a frequency-selective
transfer between two waveguides. This condition leads to the construction
of ultra-compact photonic crystal channel add/drop filters, which is of
great importance in wavelength division multiplexing for communication
purposes. In addition, the paper provides one of the first theoretical
treatments of waveguide-cavity interaction in photonic crystals.
Waveguide-cavity interaction has since been very extensively exploited to
create many different kinds of functional devices.
Your most-cited paper in our analysis is the 1999
Phys. Rev. B paper, "Guided modes in photonic crystal slabs,"
(60: 5751-8, 15 August 1999). Would you talk a little bit about
this paper's methods, findings, and conclusions?
In the late 1990s, experimentalists were starting to explore the photonic
crystal slab structures. These structures typically consist of
two-dimensional array of air holes introduced into a high-index guiding
layer. This paper, together with an earlier paper (Phys. Rev.
Lett. 78: 3294, 1997), and a subsequent paper (Phys. Rev. B
62, 8812, 2000), represented some of the foundational analysis of these
slab structures. In this set of papers, in addition to Professor John
Joannopoulos, I have mainly collaborated with Steven Johnson and Pierre
At the time these papers were published, there were substantial confusions
in the community on whether such a structure can guide light or not. These
papers showed that in spite of the large in-plane index contrast, as long
as the index of the guiding layer is much larger than the surrounding
regions, there exist exact guiding modes that are intrinsically
These papers also provided many detailed considerations on designing these
slab structures for various purposes, including, for example, the
structures that achieve a large in-plane band gap. These days, most of the
photonic crystal devices are based on exactly the kind of slab structures
that were analyzed in these papers.
One of your more recent papers is the 2008
Appl. Phys. Lett. article, "Aligning microcavity resonances
in silicon photonic crystals with laser pumped thermal tuning," (92:
Art. no. 103114, 2008). Would you discuss the findings of this
"...the idea of photonic crystals is
very powerful, and can have substantial
impacts on practically every aspect's of
Starting in 2004, together with M. F. Yanik, who was then a Ph.D. student
in my group, we started to explore dynamic photonic crystal for the purpose
of stopping, storing, and time-reversing optical pulses. (Phys. Rev.
Lett. 92: 083901; Phys. Rev. Lett. 93: 173903; Phys. Rev.
Lett. 93: 233903) All these applications, and many others, rely upon
the capability to create coherent interaction and interference between two
different cavities. For that purpose, two cavities need to have the same
frequency, to an accuracy much smaller compared with the cavity linewidth.
This is difficult to accomplish by nanofabrication alone. This paper shows
a thermal tuning scheme to align two cavity resonances, which is very
effective in overcoming fabrication inaccuracy.
What are the practical applications (or hoped-for
applications) for photonic crystals?
These days you can find applications of photonic crystals in practical
every aspect of optical technology. A few examples include communication,
sensing, solid-state lighting, and energy applications.
What should the "take-home" lesson be about your
In this area, those theorists that ultimately have had impacts were almost
always those who understood the experimental reality, and yet at the same
time were not constrained by what the experimentalists could do at that
particular moment. Instead, they always sought to think deeper and to look
beyond. Theory matters a lot, even, and perhaps, in particular in a field
like this that is strongly influenced by many practical
Shanhui Fan, Ph.D.
Stanford, CA, USA
Keywords: photonic crystals, waveguides, waveguide-cavity
interaction, photonic crystal slabs, optical pulses.