Graduate Student Profiles

Marten Beels from Grand Rapids, MI (BA from Goshen College and BSE from Messiah College) is working with Professor Biaggio to study the linear and non-linear optical properties of small, organic molecules.  He also enjoys racing bikes, both road and cyclocross, for Lehigh’s collegiate team and the local Bethlehem team, Lamprey Systems.


DFWM (Degenerate four wave mixing) is one experimental technique used to measure some non-linear optical properties. The molecules can be vapor deposited to form beautiful thin films to study their solid state properties and demonstrate interesting physics and new types of optical devices

Figen Bekisli is a PhD student from Turkey, with an undergraduate degree from Middle East Technical University . She is currently working with Prof. Stavola in the area of experimental solid state physics . Her research involves analysis of hydrogen and hydrogen related defects in semiconductors by vibrational IR spectroscopy. She is particularly interested in transparent metal oxides such as SnO2, TiO2 and ZnO.

(left to right ) Figen Bekisli and Lanlin Wen, graduate students at Lehigh University, and Kelsey Potter, an undergraduate student from the University of Tulsa, are shown making low-temperature, IR-absorption spectroscopy measurements  to investigate the microscopic structures and properties of impurities in semiconductors

(left) Polarization dependence of the IR spectrum of SnO2 treated in an H2 ambient.  (right) Structure of an (O-H)2 center in which two H atoms are bonded near an interstitial Sn atom.  The blue atoms are oxygen, the black atoms are tin.

F. Bekisli, M. Stavola, W. B. Fowler et al., H impurities and shallow donors in SnO2 studied by IR spectroscopy, Phys. Rev. B, 84 (2011).

L. Wen, F. Bekisli, M. Stavola, W. B. Fowler et al., Detailed structure of the H-N-H center in GaAsyN1-y revealed by vibrational spectroscopy under uniaxial stress, Phys. Rev. B, 81, (2010).

Ling Cai studies the disordered relaxor ferroelectric system. Polar Nanoregions (PNRs) in these systems give rise to frequency-dependent dielectric dispersion. Primary experimental techniques include dielectric spectroscopy, Raman spectroscopy, neutron scattering.



Ling Cai, PhD candidate

Advisor: Prof. Jean Toulouse
BS, Applied Physics, 2008, California State University, San Bernardino
MS, Physics, 2011, Lehigh University




Tyler Drake is a graduate student from Norwich, Vermont. He obtained his undergraduate degree in physics at Drew University in New Jersey. In his research with Prof. Vavylonis he develops analytical and computational models based on non-linear dynamics to understand how cells break symmetry for polarized growth. He also enjoys basketball and motoring.







Tyler (left) with Prof. Vavylonis (right) visiting biologists Fulvia Verde and Maitreyi Das at the University of Miami.

T. Drake and D. Vavylonis, "Cytoskeletal Dynamics in Fission Yeast: A Review of Models for Polarization and Division," HFSP J., 4 122-130 (2010).

Pavel Irkhin, a graduate student from Moscow Engineering Physics works with Prof. Biaggio. He uses lasers to study organic molecular single crystals of rubrene which exhibit anisotropic exciton diffusion.

P. Irkhin and I. Biaggio, Phys. Rev. Lett. 107, 017402 (2011)





















Brian Knorr is a graduate student from Prospect Park, New Jersey. He obtained his undergraduate degree in physics at Ramapo College of New Jersey. In his research with Prof. Dierolf he uses Raman spectroscopy to  study laser-induced crystallization in glasses. He enjoys hockey, softball, whistling, and chocolate chip cookies.

Brian (coke) with Brandon Mitchell (champagne), Nate Woodward (no drink), and  Prof. Dierolf (wine)  celebrating Nate’s hooding.


Raman spectra from various points on a LaBGeO5 sample containing femto-second laser written crystal lines. T to B:  glass region, edge of crystal line, just off center, center of line

 CW laser written lines

G. Stone, B. Knorr, V. Gopalan, and V. Dierolf, “Frequency shift of Raman modes due to an applied electric field and domain inversion in LiNbO3," Phys. Rev. B, 84 134303 (2010).



Wei Li is a graduate student from China. He obtained his B. S. Physics at the University of Science and Technology of China. He works with Prof. James Gunton to study the equilibrium and non-equilibrium properties of self-assembly processes for different models of proteins, polymers and colloidal particles. 







Photo: Wei (right) with peer in Lehigh at Phi Beta Delta induction, 2009. Image: Nanochain formation for Bipolar model.

Wei Li has been the president of the Lehigh Chinese Student and Scholars Association in 2010-2011. He received the Lehigh Graduate Life Leadership Award in 2011. 

Selected publications:
W. Li, Y. Liu, T. Pérez, J. Gunton, C. Sorensen and A. Chakrabarti, " Kinetics of nanochain formation in a simplified model of amelogenin biomacromolecules”, Biophys. J., 101, 10 (2011)
W. Li, J. Gunton, S. Khan, J. Schoelz, and A. Chakrabarti, “Brownian dynamics simulation of insulin microsphere formation from break-up of a fractal network”, J. Chem. Phys. 134, 024902 (2011)

Amber Marsh Boyer, a graduate student from Virginia, completed her undergraduate degree in Applied Physics at Christopher Newport University. She is working with Prof. McSwain to investigate the physical properties of B and Be stars in the double cluster NGC 869 and NGC 884. They are also investigating the temperature and density structure of known Be star disks.



Right: In front of the 0.9m telescope at CTIO in Chile.

Left: Spectra of Be star (top) and normal B-type star (bottom).     






Artist Bill Pounds illustration of a classical Be star.





A. N. Marsh Boyer & M. V. McSwain “Analysis of the B and Be Stars of the Double Cluster h and χ Persei”, 2011, Four Decades of Research on Massive Stars, (2011) in press

Nikola Ojkic from the University of Novi Sad, Serbia, is working in the area of theoretical biophysics with Professor Vavylonis. He develops numerical simulations of the self-organization of the contractile ring during cell division.







Monte Carlo simulation of a polymerizing contractile meshwork of actin filaments in the presence of cross-linkers

N. Ojkic and D. Vavylonis, "Kinetics of Myosin Node Aggregation into a Contractile Ring," Phys. Rev. Lett. 105 048102 (2010).
N. Ojkic, J.-Q. Wu and D. Vavylonis, "Model of Myosin Node Aggregation into a Contractile Ring: the Effect of Local Alignment," J. Phys. Cond. Matter 23, 374103 (2011).

Jonathan Poplawsky has received his B.S. in physics from The University of Scranton and is originally from Danville, PA.  He is currently working under the guidance of Professor Volkmar Dierolf, and has developed a confocal microscope that simultaneously excites a sample with an electron and laser beam while collecting the emission within a 2μm Spot.  He uses this instrument to study RE ions doped in GaN as well as GaN/InGaN quantum wells for LED applications.







Photos: Jonathan at the 2011 MAS Cathodoluminescence Topical Conference (left). The combined excitation experimental setup as it sits on an Oxford Low Temperature SEM Stage to be inserted into a JEOL 6400 (right).

J. Poplawsky et. al., “Nature and Excitation Mechanism of the Emission-dominating Minority Eu-center in GaN Grown by Organometallic Vapor-phase epitaxy” Mater. Res. Soc. Symp. Proc. 1342 (2011)

Matthew Smith (B. S. Physics and Mechanical Engineering, California State University Chico) works with Prof. Dimitris Vavylonis to model the dynamics of actin proteins in motile cells by analyzing single molecule fluorescent microscopy images of live cells from the lab of Naoki Watanabe (Tohoku University, Japan).




Matthew (yellow shirt) at the 61st Lindau Nobel Laureate Meeting in Germany, 2010. Second photo: Single actin molecule tracking within a live cell



"Interactive, Computer-Assisted Tracking of Speckle Trajectories in Fluorescence Microscopy: Application to Actin Polymerization and Membrane Fusion," M. B. Smith, E. Karatekin, A. Gohlke, H. Mizuno, N. Watanabe, and D. Vavylonis, Biophysical Journal 101:1794(2011)