Started Olympiad in high school, I have been

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Last updated: May 19, 2019

Started as a student competitor in Chinese Physics Olympiad in high school, I have been reallyfascinated by the beauty of “simplicity” in the world of physics.

In many cases, a complicated issuein the real world could be abstracted as simplified equations for mathematical analysis andsimultaneously, the scientific ways of thinking in physics study could be widely used to solveproblems in various aspects of our daily life and scientific research. After high school, I continuedmy journey in physics in the School of Physics at Peking University, which is one of the mostrespected hallowed halls of physics in mainland China. The study in Peking University provides mea thorough grounding in both theoretical and experimental physics, and also consolidates a series ofbasic research skills for me. During the past three years, I was actively involved in severalresearching projects at Peking University, which provide me a decent knowledge regarding the fieldof low-dimensional materials (especially for carbon nanotubes and graphene) and get me welltrained in experimental techniques including polarization modulation, optical imaging andspectroscopy. Also, I conducted a three-month research internship at University of California, LosAngeles last summer, which dramatically enhanced my programming skills, especially in imagereconstruction. I believe my competence acquired from all these experiences will get me wellprepared for my future researches.I started my lab work in Prof. Kaihui Liu’s group in Peking University in my second collegeyear.

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After one semester’s basic training in experimental and programming skills, I was assigned tohandle a training project individually. The project was to examine how tension would influence theRaman peaks of MoS2. The practical challenge was to elaborately tune the tension on monolayerMoS2. To achieve that, I designed and fabricated a microstructure in micromanipulator, by which Icould regulate the tension on MoS2 samples by controlling the deformation of substrate. With it, Imeasured the behavior of low-wavenumber Raman spectrum and Photoluminescence (PL) spectrumin MoS2 with different tension, and successfully identified a shift of the A1g and E2g peak in MoS2’sRaman spectrum.

This is my first independent project in a research lab and it took me two monthsto nail it. This short but happy journey motivated me to further challenge myself on scientificquestions.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 individualcarbon nanotubes and acquired their absorption spectra. Then, we studied the interactions of carbonnanotubes and their substrates by examining the absorption spectra difference between hangingnanotubes and on-substrate nanotubes. After that, we published a paper at Chemistry – A EuropeanJournal 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 tocontrol the polarization of incident light. However, if the polarizers are strictly perpendicularlyplaced, the spectrum would behave in a weird way. Intrigued by this unique phenomenon, Iinvestigated 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 thetheory interprets our experimental results quite well.

It reveals that if the polarizers are strictlyperpendicular, what we measured are no longer the carbon nanotubes’ absorption properties, but thereal part information of the complex electric susceptibility, while the latter one has never beendetermined experimentally in individual carbon nanotubes! I talked to my mentor Prof. Liu on thissurprising finding and he encouraged me to dig deeper. Collaborating with a graduate student inProf. Liu’s lab, we successfully developed a detecting method that can give a high-throughputdetection of the full information of the complex electric susceptibility in individual carbonnanotubes based on the theory we developed. Currently, we have wrapped up our story and areseeking 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 threemonthresearch 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 MachineLearning. To eliminate the discontinuities in the reconstructed phase map and improve thereconstruction quality, I did a literature search about phase unwrapping algorithms and selectedseveral candidates. By testing the performance of each candidate, I refined a fast and robust phaseunwrapping algorithm and implemented it into our image reconstruction code. The results werequite 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 bea very labor-intensive work if I just manually label those particles one by one in a holographicreconstruction map. To avoid that, I employed image registration algorithm and mapped theholographic reconstruction map to a microscope image. In this way, the labeling process could beconducted in microscope images, which would be more efficient and accurate than a human’sjudgement. Compared to the experimental and theoretical work in Peking University, the study inUCLA helped me a lot in my programming skills.In consideration of its excellent faculty and facilities, the Department of ElectricalEngineering’s graduate program at Yale would be a wonderful platform for me to continue my studyand research. Specifically, I am especially interested in Prof.

Fengnian Xia’s research on grapheneplasmonics and photonics, along with Prof. Mark A. Reed’s research on nanowires electronics andphotonics, since I have been working on photonics in low-dimensional materials (like graphene andcarbon nanotubes) for two years at Peking University, and I am truly absorbed by those fancymaterials with unique optical, electronical, thermal, and mechanical properties. I believe I cancontribute 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 jointhe Department of Electrical Engineering at Yale. I believe my strong background in both theoreticaland experimental physics and my hands-on experiences will ensure my success in this wonderfulprogram.

  

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