Research
QD and QDM hole spin qubit simulation and 2-D electric field device
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This project involves single InAs/GaAs quantum dots (QD) and quantum dot molecules (QDM). These are self-assembled semiconductor nanostructures grown by molecular beam epitaxy (MBE) that can trap a single electron or hole in a 3-D potential well. Their superb optical quality gives them a wide range of optoelectronic applications, such as vertical cavity surface emitting lasers (VCSEL), sub-bandgap solar cells, LED, sensors, and quantum information/computing. 
We are interested in their quantum information applications using a single hole spin state trapped in a QD. Tight-binding simulation and finite Hamiltonian perturbation matrix are used to calculate the hole spin state in a single QD and QDM. We discovered that a single hole spin state has geometric textures that evolve with external electric and magnetic fields. We also design, fabricate, and characterize devices that can apply both vertical and lateral (2-D) electric field to a single QD and QDM nanostructure. A time-resolved photoluminescence setup has been developed in the NIR wavelength region for CZTS solar cell carrier life-time characterizations. We are also developing and optimizing a direct laser inscription setup for waveguide fabrications on chalcogenide thin films.
Quantum dot heterostructures for photon upconversion
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We are currently developing materials for photon upconversion with the goal of advancing solar cell technology. A major limiting factor of energy conversion efficiency is that current photovoltaics cannot utilize the full solar spectrum, meaning that sub-bandgap energy light passes through the device without being converted into electricity. The goal of this project is to create a material that can efficiently absorb these low-energy photons and emit high-energy photons, which can then be reflected through and utilized by a solar cell. Use of a broader range of light will result in more 
energetically and economically efficient renewable energy technology. The materials we are synthesizing to achieve this goal are quantum heterostructures, in which two quantum dots (QDs) with different bandgaps are separated by a wide-bandgap nanorod. The smaller bandgap QD sequentially absorbs two or more low-energy photons. Excited carriers then relax into the larger bandgap QD, where they can radiatively recombine to emit a single high-energy photon. This design has been found to achieve photon upconversion, though there is significant room for improvement in upconversion efficiency. Our current focus is working towards higher control of the shape, structure, and stability of our materials, which will allow for future incorporation into photovoltaic devices.
Development of a room-
Click here to watch a video about the lab work related to this project.
This project is aimed for developing a Time-domain Terahertz Spectroscopy (TDTS) system which can be used to study the spin states in topological insulators.
Photonic incorporation in scalable quantum optoelectronic device design
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In this project we focus on incorporating current quantum dot molecule (QDM) understanding with photonic structures in order to design a scalable device platform. A hexagonal photonic crystal is defined vertically due to total internal reflection in a thin membrane and laterally due to a photonic bandgap produced by a hexagonal array of air holes. Our photonic structure is produced mainly through local defects in this structure creating cavities and waveguides. QDMs positioned internally to these cavities and tuned using electric field can then be addressed optically using this structure.
Our current work involves design of a fabrication process 
that is relatively unaffected by feature size as well as characterization techniques such as resonance fluorescence.
Development of a low-temperature system for the optical study of magnon and spin transfer torque dynamics
This project is focused on developing a measurement system that can be used to study spin orbital torque dynamics in novel magnetic materials or heterostructures. This analysis is performed at low temperature using DC or time-resolved magneto-optical Kerr effect (MOKE) spectroscopy. This system has been developed to study spin orbital torque in a variety of magnetic heterostructures.
