Started Olympiad in high school, I have been

Started as a student competitor in Chinese Physics Olympiad in high school, I have been really
fascinated by the beauty of “simplicity” in the world of physics. In many cases, a complicated issue
in the real world could be abstracted as simplified equations for mathematical analysis and
simultaneously, the scientific ways of thinking in physics study could be widely used to solve
problems in various aspects of our daily life and scientific research. After high school, I continued
my journey in physics in the School of Physics at Peking University, which is one of the most
respected hallowed halls of physics in mainland China. The study in Peking University provides me
a thorough grounding in both theoretical and experimental physics, and also consolidates a series of
basic research skills for me. During the past three years, I was actively involved in several
researching projects at Peking University, which provide me a decent knowledge regarding the field
of low-dimensional materials (especially for carbon nanotubes and graphene) and get me well
trained in experimental techniques including polarization modulation, optical imaging and
spectroscopy. Also, I conducted a three-month research internship at University of California, Los
Angeles last summer, which dramatically enhanced my programming skills, especially in image
reconstruction. I believe my competence acquired from all these experiences will get me well
prepared for my future researches.

I started my lab work in Prof. Kaihui Liu’s group in Peking University in my second college
year. After one semester’s basic training in experimental and programming skills, I was assigned to
handle a training project individually. The project was to examine how tension would influence the
Raman peaks of MoS2. The practical challenge was to elaborately tune the tension on monolayer
MoS2. To achieve that, I designed and fabricated a microstructure in micromanipulator, by which I
could regulate the tension on MoS2 samples by controlling the deformation of substrate. With it, I
measured the behavior of low-wavenumber Raman spectrum and Photoluminescence (PL) spectrum
in MoS2 with different tension, and successfully identified a shift of the A1g and E2g peak in MoS2’s
Raman spectrum. This is my first independent project in a research lab and it took me two months
to nail it. This short but happy journey motivated me to further challenge myself on scientific
questions.
My second project is about optical imaging and spectroscopy of one-dimensional materials.
Based on polarization modulation, we succeed in high-throughput optical imaging of individual
carbon nanotubes and acquired their absorption spectra. Then, we studied the interactions of carbon
nanotubes and their substrates by examining the absorption spectra difference between hanging
nanotubes and on-substrate nanotubes. After that, we published a paper at Chemistry – A European
Journal to introduce our detection method and I am the co-first author of this paper.
In Prof. Liu’s lab, in order to acquire the absorption spectra of individual carbon nanotubes,
the canonical method is to use two nearly ?/2 crossed polarizers with a small deviation angle to
control the polarization of incident light. However, if the polarizers are strictly perpendicularly
placed, the spectrum would behave in a weird way. Intrigued by this unique phenomenon, I
investigated the principle of polarization modulation and proposed an improved approximate model.
Different from the previous model, our model can better explain how the orientation of polarizers would influence the absorption spectrum in our experiments. We were very happy to find that the
theory interprets our experimental results quite well. It reveals that if the polarizers are strictly
perpendicular, what we measured are no longer the carbon nanotubes’ absorption properties, but the
real part information of the complex electric susceptibility, while the latter one has never been
determined experimentally in individual carbon nanotubes! I talked to my mentor Prof. Liu on this
surprising finding and he encouraged me to dig deeper. Collaborating with a graduate student in
Prof. Liu’s lab, we successfully developed a detecting method that can give a high-throughput
detection of the full information of the complex electric susceptibility in individual carbon
nanotubes based on the theory we developed. Currently, we have wrapped up our story and are
seeking a good journal to get it published. I would be the co-first author for this work.
In addition to the work inside the campus of Peking University, I was very lucky to find a threemonth
research internship in Prof. Aydogan Ozcan’s lab at University of California, Los Angeles,
working on Automatic Detection of Bio-Aerosols Based on Lens-free Imaging and Machine
Learning. To eliminate the discontinuities in the reconstructed phase map and improve the
reconstruction quality, I did a literature search about phase unwrapping algorithms and selected
several candidates. By testing the performance of each candidate, I refined a fast and robust phase
unwrapping algorithm and implemented it into our image reconstruction code. The results were
quite good as unnatural discontinuities were eliminated successfully.
In UCLA, I was also involved in another work to build a training library for machine learning.
My job was to conduct the image reconstruction and label > 3,000 bio-aerosol particles. It would be
a very labor-intensive work if I just manually label those particles one by one in a holographic
reconstruction map. To avoid that, I employed image registration algorithm and mapped the
holographic reconstruction map to a microscope image. In this way, the labeling process could be
conducted in microscope images, which would be more efficient and accurate than a human’s
judgement. Compared to the experimental and theoretical work in Peking University, the study in
UCLA helped me a lot in my programming skills.
In consideration of its excellent faculty and facilities, the Department of Electrical
Engineering’s graduate program at Yale would be a wonderful platform for me to continue my study
and research. Specifically, I am especially interested in Prof. Fengnian Xia’s research on graphene
plasmonics and photonics, along with Prof. Mark A. Reed’s research on nanowires electronics and
photonics, since I have been working on photonics in low-dimensional materials (like graphene and
carbon nanotubes) for two years at Peking University, and I am truly absorbed by those fancy
materials with unique optical, electronical, thermal, and mechanical properties. I believe I can
contribute with my physics background and hands-on experience in working on them.
As such, I sincerely look forward to your kind review of my application and truly hope to join
the Department of Electrical Engineering at Yale. I believe my strong background in both theoretical
and experimental physics and my hands-on experiences will ensure my success in this wonderful
program.  

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