Bio

 

PhD Electrical Engineering, University of North Carolina, Charlotte, 2006. Doctoral advisor: Raphael (Ray) Tsu (UNCC | Wikipedia)
MS Applied Physics, University of North Carolina, Charlotte, 2001.
BS Physics, Illinois Institute of Technology, 1996

“Less is more.” – Mies van der Rohe

RESEARCH SUMMARIES

The Classical Electrostatic Periodic Table | Thomson Problem

In my theoretical work concerning the classical and quantum mechanical properties of spherical quantum dots, I discovered a unique distribution of electrostatic energies that coincides with many physical and chemical properties of atomic systems.

The Classical Electrostatic Periodic TableAdditional Information: 10.1016/j.elstat.2013.10.001

Among many correspondences between the Thomson problem (Thomson Problem | Wikipedia) and atomic electron structure are salient features that coincide with quantum electron shell filling in addition to the only “doubly anomalous” shell-filling rule violator, palladium (Pd, Z=46) in which the “outermost” two electrons occupy an s orbital instead of the corresponding d orbital. An (older) informative summary of this work appears as a large poster (Periodic Table | Periodic Table Database) that includes brief discussion on topics including ionization, electron hardness, quantum numbers, and several coincidences with nuclear phenomena.
Quantum Informatics Research Group | QIRG

A Bell State Oscillator (BSO) is designed to produce linear combinations of Bell states as values. This allows for the possible construction of a basic synchronization building block over a quantum channel that avoids delays present in conventional electronic systems. The BSO has the potential to be employed in a wide variety of future applications.

The radix-4 Chrestenson gate (C4), allows a radix-4 qudit originally in a basis to evolve into a quantum state of equal superposition. The existing implementation of a C4 include tabletop glass and 4-port nanophotonic coupler at the intersection of active optoelectronic ridge waveguides (see the “Two Dimensional Active Lattice Filter” below).

[top left] Chrestenson gate (four-port coupler). [top right] Schematic architecture for Bell state oscillator (BSO). [bottom] Quantum circuit for Bell state oscillator including four quantum state generators.
Additional Information:
Square Dielectric THz Waveguide

A holey cladding dielectric waveguide fabricated of the polymer TOPAS was designed to be single mode across the broad frequency range of 180 GHz to 360 GHz using finite-difference time domain simulation and to robustly support simultaneous TE and TM mode propagation. The square fiber geometry was realized by pulling through a heat distribution made square by an appropriate furnace design. The transmitted mode profile was imaged using a vector network analyzer (VNA) with a pinhole at the receiver module. Good agreement between the measured mode distribution and the calculated mode distribution were demonstrated.

Additional Information: 10.1364/OE.24.014951
Two-Dimensional Active Lattice Filter

In our research supported by DARPA at the University of Texas at Dallas, we developed a two-dimensional active optical lattice filter based on indium phosphide (InP) ridge waveguides. Using a “4×4 nanophotonic coupler” at the intersection of waveguides, coherent light may be directed along all pathways. 4 x 4 Nanophotonic CouplerTransmitted light may be coupled to an ongoing by virtue of evanescent coupling while light may also be reflected to the left, right, and backward. The task represented several fabrication challenges including the successful integration of nanoscale (100nm wide) optical couplers (defined by focused ion beam (FIB) and reactive ion etch (RIE)) which were subsequently backfilled (4μm depth) with aluminum oxide (Al2O3) by atomic layer deposition (ALD).

          I introduced “nanoalignment markers,” positioned at 45º to the waveguides, to precisely position the nanophotonic couplers in relation to the 2μm-wide InP waveguides and the circular intersection which was subsequently used as a “virtual substrate” for proper processing of the nanophotonic coupler including deep trench etching and subsequent dielectric backfilling. The high-aspect etch ratio (40:1) is considered “best in class”.

          Compared to conventional directional couplers which require ~1mm of real estate for optical coupling between waveguides, nanophotonic couplers require less than 10μm.

Additional Information: 10.1016/j.mejo.2008.11.035
Solid-Metal-Mediated Epitaxy | Silicon-on-Insulator
I demonstrated a novel microelectronics semiconductor fabrication process used to produce localized regions of silicon-on-insulator (SOI) including single-crystal, highly p-doped silicon (p-Si) over buried silicon dioxide (SiO2) using a solid metal aluminum (Al) film. At 400ºC, Si is deposited by molecular beam epitaxy and diffuses with an average diffusion length of ~1μm in solid Al. The diffused silicon grows epitaxially at the buried Al-Si interface, pushing theSilicon on Insulator as-fabricated using solid metal mediated epitaxy Al film upward, then grows laterally over regions of oxide (SiO2).

As shown in the transmission electron microscope image to the left using electron diffraction, the result is a single crystal Si thin film over the oxide region.
Manufacture of High-Precision PDMS Microstructures
microspheres I designed a fabrication process by which multiple polymeric microspheres are manufactured. Originally designed for use in an all-optical neuronal stimulator/sensor package, the process was also used to provide precisely-designed cushioned “nubs” on the end of glass optical fibers used in brush optodes for functional near-infrared spectroscopy (fNIRS).

 PUBLICATIONS
See Google Scholar

          Book Chapters

    1. R. Tsu & T. LaFave, Jr “Role of Symmetry in Conductance, Capacitance, and Doping of Quantum Dots” Ch. 1 in The Wonder of Nanotechnology: Quantum Optoelectronic Devices and Applications M. Razeghi, L. Esaki, and K. von Klitzing, Eds., SPIE Press, Bellingham, WA, pp. 3-38 (2013).

          Peer-Reviewed Articles

    1. N. Aflakian, N. Yang, T. LaFave Jr., K. 0, and D. MacFarlane “Square Dielectric THz Waveguides” Opt. Exp. 24(13) (2016). DOI: 10.1364/OE.24.014951
    2. T. LaFave Jr. “Discrete Transformations in the Thomson Problem” J. Electrostatics (2014). DOI: 10.1016/j.elstat.2013.11.007
    3. T. LaFave Jr. “Correspondence between the Classical Electrostatic Thomson Problem and Atomic Electronic Structure” J. Electrostatics 71 1029 (2013). DOI: 10.1016/j.elstat.2013.10.001
    4. B. Cheek, M. Dabkowski, A. El Nagdi, L. R. Hunt, T. P. LaFave Jr, K. Liu, D. L. MacFarlane, & V. Ramakrishna “Analysis of a Polynomial System Arising in the Design of an Optical Lattice Filter Useful in Channelization” Acta Applicandae Mathematicae 118(1) 107-123 (2012). DOI: 10.1007/s10440-012-9680-8
    5. D.L. MacFarlane, M.P. Christensen, K. Liu, T. LaFave Jr, G.A. Evans, N. Sultana, T.W. Kim, J. Kim, J. B. Kirk, N. Huntoon, M. Dabkowski, L.R. Hunt, & V. Ramakrishna “Four-Port Nanophotonic Frustrated Total Internal Reflection Coupler” IEEE Photon Technol Lett 24(1) 58-60 (2012). DOI: 10.1109/LPT.2011.2172204
    6. D. L. MacFarlane, M. P. Christensen, A. E. Nagdi, G. A. Evans, L. R. Hunt, N. Huntoon, J. Kim, T. W. Kim, J. Kirk, T. LaFave Jr, K. Liu, V. Ramakrishna, M. Dabkowski, & N. Sultana “Experiment and Theory of an Active Optical Filter” J. Quant Electronics 48(3) 307-317 (2012). DOI: 10.1109/JQE.2011.2174615
    7. T. LaFave Jr. “Discrete Charge Dielectric Model of Electrostatic Energy” J. Electrostatics 69 414-418 (2011). DOI: 10.1016/j.elstat.2011.06.006
    8. A. El Nagdi, K. Liu, T. P. LaFave Jr, L. R. Hunt, V. Ramakrishna, M. Dabkowski, D. L. MacFarlane & M. P. Christensen “Active integrated filters for RF-photonic channelizers” Sensors 11(2) 1297-1320 (2011). DOI: 10.3390/s110201297
    9. N. Sultana, W. Zhou, T. LaFave Jr & D. L. MacFarlane “HBr based inductively coupled plasma etching of high aspect ratio nanoscale trenches in InP: Considerations for photonic applications” J Vac Sci B 27(6) 2351-2356 (2009). DOI: T. LaFave Jr & R. Tsu “The value of monophasic capacitance of few-electron systems” Microelectron J 40 791-795 (2009). DOI: 10.1016/j.mejo.2008.11.035
    10. T. LaFave Jr & R. Tsu “Capacitance: A property of nanoscale materials based on spatial symmetry of discrete electrons” Microelectron J 39(3-4) 617-623 (2008). DOI: 10.1016/j.mejo.2007.07.105
    11. J. Zhu, T. LaFave Jr & R. Tsu “Capacitance of Few Electron Dielectric Spheres” Microelectron J 37 1293-1296 (2006). DOI: 10.1016/j.mejo.2006.07.013

           Conference Proceedings

    1. H. Kumar, H. Yao, T. Ei, N. Ashrafi, T. LaFave Jr., S. Ashrafi, D.L. MacFarlane, and R. Henderson, “Physical Phaseplate for the Generation of a Millimeter-Wave Hermite-Gaussian Beam” 2016 IEEE Radio and Wireless Symposium (RWS) 234-237 (2016).
    2. D. L. MacFarlane, M. P. Christensen, A. E. Nagdi, G. A. Evans, L. R. Hunt, N. Huntoon, J. Kim, T. W. Kim, J. Kirk, T. P. LaFave, K. Liu, V. Ramakrishna, M. Dabkowski, & N. Sultana “Two dimensional optical lattice filters with gain: Fabrication and experimental results” Quant. Electronics Conf. & Lasers and Electro-optic (CLEO/IQEC/PACIFIC RIM) 1018-1020 (2011).
    3. D. L. MacFarlane, M. P. Christensen, L. R. Hunt, J. Kim, T. W. Kim, T. P. LaFave, K. Liu, A. E. Nagdi, N. Sultana, V. Ramakrishna & M. Dabkowski “Active Optical Lattice Filters with Nanophotonics Four-Port Couplers” 15th OptoElectronics and Communications Conference (OECC2010) Technical Digest July 2010 7D3-4 (2010).
    4. M. P. Christensen, D. L. MacFarlane, L. R. Hunt, J. Kim, T. W. Kim, T. P. LaFave, K. Liu, A. El Nagdi, N. Sultana, V. Ramakrishna, N. Huntoon, & M. Dabkowski “Active lattice filter with nanophotonic FTIR-couplers for integrated photonic channelizer” Photonics Global Conference (PGC) 1-4 (2010).
    5. D. L. MacFarlane, L. R. Hunt, V. Ramakrishna, W. Zhou, N. Sultana, & A. Stark “Chip-Scale Analog Optical Signal Processing” Conf. Proc. – LEOS Ann. Meeting, 437-438 (2008).
    6. “A New Definition of Capacitance of Few Electron Systems” PIERS Proceedings, Hangzhou, China, March 24-28, 1269-1274 (2008) with R. Tsu.

“Take a brighter path.”