Zhou Lab

Research

Vision

Scaling of lasers, detectors, and solar cells with extreme performance and novel functionalities for integrated silicon photonics and flexible optoelectronics.

Approach

Research focuses on light-matter interactions based on heterogeneous integration of low dimensional quantum confined semiconductor materials with photonic crystal and metamaterial optical cavities. Various heterogeneous integration processes are also being explored in micro- and nano-processed structures. Ultimately the group explores extreme device structures and functional, through coupled experimental and theoretical investigations, and extensive collaborations with groups from a wide range of disciplines.

Research Approach Venn Digram

Major Research Areas

Area I: Scaling of photonic crystal membrane lasers for on-chip integration

The creation of silicon based light sources has been a major research and development effort world-wide. The availability of the practical on-silicon lasers will enable a new generation of integrated photonic and electronic components and systems, which will be more cost-effective and energy efficient, and will perform better. Zhou group and collaborators have been working on a range of photonic crystal based surface-emitting membrane lasers for on-chip integration, with a focus on cavity and gain media scaling with ultimate goal of extreme energy efficiency and high capacity data transfer. Over the years, the group has been working on the following types of lasers:

Ia: Membrane reflector vertical-cavity surface-emitting lasers (MR-VCSEL):

Different from the conventional vertical-cavity surface-emitting lasers (VCSELs), where the cavity is formed with two distributed Bragg reflectors (DBRs), MR-VCSEL consists of two single layer photonic crystal membrane reflectors (MRs), which can be built directly on Silicon or other dielectric materials. A gain medium (e.g. quantum well heterostructure QW) is sandwiched in between these two Si-MRs. These lasers can be built-directly on Si for on-chip integration. Additionally, different wavelength MR-VCSELs can be achieved easily based on photonic crystal scaling principles.

Membrane-reflector vertical-cavity surface-emitting laser

Related publications:

  1. H. Yang, S. Chuwongin, Z. Qiang, L. Chen, H. Pang, Z. Ma, and W. D. Zhou, “Resonance Control of Membrane Reflectors with Effective Index Engineering”, Appl. Phys. Lett. 95, 023110, (2009).
  2. Z. X. Qiang, H. Yang, S. Chuwongin, D. Zhao, Z. Ma, and W. D. Zhou, “Design of Fano broadband reflectors on SOI”, IEEE Photon. Technol. Lett. vol. 22(15), 1108 (2010).
  3. D. Zhao, Z. Ma and W.D. Zhou, “Field penetration and distribution in photonic crystal mirror cavities”, Opt. Express Vol. 18, Issue 13, pp. 14152-14158, 2010.
  4. D. Zhao, H. Yang, Z. Ma, and W. Zhou, "Polarization independent broadband reflectors based on cross-stacked gratings," Opt. Express 19, 9050-9055 (2011).
  5. H. Yang, D. Zhao, J.-H. Seo, S. Chuwongin, S. Kim, J. A. Rogers, Z. Ma, and W. Zhou, “Broadband Membrane Reflectors on Glass”, IEEE Photon. Technol. Lett. 24(6), 476-8, 2012.
  6. H. Yang, D. Zhao, S. Chuwongin, J.-H. Seo, W. Yang, Y. Shuai, J. Berggren, M. Hammar, Z. Ma and W. Zhou, “Transfer printing stacked nanomembrane lasers on silicon”, Nature Photonics 6, 615-620 (2012). AOP July 22, 2012. link to nature article
  7. D. Zhao, H. Yang, S. Chuwongin, J.H. Seo, Z. Ma and W. Zhou, “Design of photonic crystal membrane reflector based VCSELs”, IEEE Photon. J. vo.4(6), 2169 (2012) (DOI: 10.1109/JPHOT.2012.2227955).
  8. Y.-C. Shuai, D. Zhao, W. Yang, W. Zhou, J.-H. Seo, Z. Ma, G. Medhi, R. Peale, W. Buchwald and R. Soref, “Fano Resonance Membrane Reflectors from Mid-Infrared to Far-Infrared”, IEEE Photon. J. 5, (1) 2200106 (2013).
  9. A. Chadha, D. Zhao, S. Chuwongin, Z. Ma, and W. Zhou, “Polarization- and angle-dependent characteristics in two dimensional photonic crystal membrane reflectors”, Appl. Phys. Lett, vol..103, 211107 (2013).
  10. K. Balasundaram, P. K. Mohseni, Y. Shuai, D. Zhao, W. Zhou, and X. Li, “Photonic crystal membrane reflectors by magnetic field-guided metal-assisted chemical etching”, Appl. Phys. Lett. vol..103, 214103 (2013).
  11. D. Zhao, H. Yang, J.-H. Seo, Z. Ma, and W. Zhou, “Design and Characterization of Photonic Crystal Membrane Reflector Based Vertical Cavity Surface Emitting Lasers on Silicon”, Rev. Nanosci. Nanotechnol. 3, 77-87 (2014).
  12. S. Liu, D. Zhao, J.-H. Seo, Y. Liu, Z. Ma, and W. Zhou, “Athermal Photonic Crystal Membrane Reflectors on Diamond”, IEEE Photon. Technol. Lett. Vol. 27(10), 1072-5 (2015).
  13. W. Zhou, D. Zhao, Y. Shuai, H. Yang, S. Chuwongin, A. Chadha, J.-H. Seo, K. Wang, V. Liu, Z. Ma, and S. Fan, “Progress in 2D photonic crystal Fano resonance photonics (Invited review)”, Prog. Quantum. Electron. 38, 1-74 (2014).
  14. W.D. Zhou, Z. Ma, H. Yang, D. Zhao, Y.-C. Shuai, and J.-H. Seo, “Nanomembranes for Fano resonance photonic crystal based photonic devices”, in Silicon Nanomembranes: Fundamental Science and Applications, J. Rogers and J.-H. Ahn (Ed.), Wiley-VCH (2016). Print ISBN: 978-3-527-33831-3, ePDF ISBN: 978-3-527-69099-2.
Ib: On-chip photonic crystal surface-emitting lasers (PCSEL)

Based on bandedge mode in defect-free photonic crystals, large area lasing cavity is formed within the photonic crystal layer. Lasing arises from the evanescent coupled QW gain medium with the photonic crystal cavity. Such lasers can be built directly on both silicon on insulator (SOI) substrate as well as bulk silicon substrate.

On-chip photonic crystal surface-emitting lasers

Related publications:

  1. D. Zhao, S. Liu, H. Yang, Z. Ma, C. Reuterskiöld-Hedlund, M. Hammar, and W. Zhou, “Printed Large-Area Single-Mode Photonic Crystal Bandedge Surface-Emitting Lasers on Silicon:, Scientific Reports 6, 18860 (2016).
  2. S. Liu, D. Zhao, Y. Liu, H. Yang, Y. Sun, C. Reuterskiöld-Hedlund, Z. Ma, M. Hammar, and W. Zhou “Photonic Crystal bandedge membrane Lasers on Silicon”, Special Issue on Semiconductor Lasers, Appl. Opt. 56, H67-73 (2017).
  3. S. Liu, D. Zhao, X. Ge, C. Reuterskiöld-Hedlund, M. Hammar, S. Fan, Z. Ma, and W. Zhou “Lateral Size Scaling of Photonic Crystal Surface-Emitting Lasers on Silicon Substrates” IEEE Photon. J. 10(3), 4500506 (2018).
  4. A. Y. Song, A. R. K. Kalapala, W. Zhou, and S. Fan, "First-principles simulation of photonic crystal surface-emitting lasers using rigorous coupled wave analysis," Applied Physics Letters, vol. 113, p. 041106, 2018.
  5. W. Zhou, S. C. Liu, X. Ge, D. Zhao, H. Yang, C. Reuterskiöld-Hedlund, and M. Hammar, “On-chip photonic crystal surface-emitting membrane lasers (Invited)”, IEEE J. Select. Top. Quant. Electron. (in press). DOI 10.1109/JSTQE.2019.2902904
  6. X. Ge, M. Minkov, S. Fan, X. Li, and W. Zhou, "Laterally confined photonic crystal surface emitting laser incorporating monolayer tungsten disulfide," npj 2D Materials and Applications, vol. 3, p. 16, 2019/04/15 2019.
Ic: Monolayer photonic crystal lasers

Based on the same PCSEL operation principle, a heterostructure photonic crystal cavity concept was proposed for later optical confinement. A monolayer two-dimensional gain material (WS2) was integrated for the realization of monolayer photonic crystal lasers.

Monolayer photonic crystal lasers

Related publications:

  1. X. Ge, M. Minkov, S. Fan, X. Li, and W. Zhou, “Low index contrast heterostructure photonic crystal cavities with high quality factors and vertical radiation coupling”, Appl. Phys. Lett. 112, 141105 (2018); https://doi.org/10.1063/1.5026433. Editor’s Pick.
  2. X. Ge, M. Minkov, S. Fan, X. Li, and W. Zhou, "Laterally confined photonic crystal surface emitting laser based on monolayer tungsten disulfide operating at room temperature," arXiv preprint arXiv:1806.08019, 2018.

Area II: Transfer printed hybrid membrane photonics

Zhou group and collaborators have been developing membrane transfer printing process for hybrid integration of nanophotonic materials and structures with innovative features and functionalities. Two major research visions based on this process:

IIa: Hybrid integration for on-chip integration

By release functional layers from the native substrates, and transfer printing onto other substrates, heterogeneously integrated integrated photonic chips can be realized with multiple functions.

Hybrid integration for on-chip integration 3D Integrated Silicon Photonics

Related publications:

  1. W.D. Zhou, Z. Ma, H. Yang, D. Zhao, Y.-C. Shuai, and J.-H. Seo, “Nanomembranes for Fano resonance photonic crystal based photonic devices”, in Silicon Nanomembranes: Fundamental Science and Applications, J. Rogers and J.-H. Ahn (Ed.), Wiley-VCH (2016). Print ISBN: 978-3-527-33831-3, ePDF ISBN: 978-3-527-69099-2.
  2. Y. H. Jung, J.-H. Seo, W.D. Zhou and Z. Ma, “High speed, flexible electronics by use of Si nanomembranes”, in Silicon Nanomembranes: Fundamental Science and Applications, J. Rogers and J.-H. Ahn (Ed.), Wiley-VCH (2016). Print ISBN: 978-3-527-33831-3, ePDF ISBN: 978-3-527-69099-2.
  3. H. Yang, D. Zhao, S. Liu, J. Seo, Z. Ma, and W. Zhou, “Transfer Printed Nanomembranes for Heterogeneously Integrated Membrane Photonics (Invited Review)”, Special Issue in “Hybrid and Heterogeneous Technologies in Photonics Integrated Circuits”, Photonics 2, 1081-1100 (2015).
  4. B. Corbett, R. Loi, W. Zhou, D. Liu, and Z. Ma, “Heterogeneous integration of photonic components using transfer print techniques (Invited Review)”, Prog. Quantum. Electron. 52, 1-17 (2017).
  5. H. Yang, D. Zhao, J.-H. Seo, S. Chuwongin, S. Kim, J. A. Rogers, Z. Ma, and W. Zhou, “Broadband Membrane Reflectors on Glass”, IEEE Photon. Technol. Lett. 24(6), 476-8, 2012.
  6. W. Zhou, Z. Ma, S. Chuwongin, Y.-C. Shuai, J.-H. Seo, D. Zhao, H. Yang, and W. Yang, “Semiconductor nanomembranes for integrated silicon photonics and flexible Photonics (Invited)”, Opt. Quant. Electron. 44, 605 (2012), Special Issue on Photonic Integration, DOI 10.1007/s11082-012-9586-8, 2012.
  7. T.H. Chang, W. Fan, D. Liu, Z. Xia, Z. Ma, S. Liu, L. Menon, H. Yang, W. Zhou, J. Berggren, M. Hammar, “Selective Release of InP Heterostructures from InP Substrates”, J. Vac. Sci. Technol. B 34, 041229 (2016).
  8. M. Kim, J.-H. Seo, D. Zhao, S.-C. Liu, K. Kim, K. Lim, W. Zhou, W. Waks and Z. Ma, “Transferrable single crystalline 4H-SiC nanomembranes”, Journal of Materials Chemistry C, 5, 264 (2017). DOI: 10.1039/C6TC04480H, Inside Front Cover. Selected as a Hot Article for 2016 in the journal.
  9. Y. Shuai, D. Zhao, C. Stambaugh, N. Zimmerman, J. Lawall, and W. Zhou, “Coupled Bi-layer Photonic Crystal Slab Electro-optic Spatial Light Modulators”, IEEE Photon. J. 9, 7101411 (2017). DOI: 10.1109/JPHOT.2017.2675619 .
IIb: Flexible photonics and optical sensors
Flexible and Bioresorbable Photonics

Related publications:

  1. Z. Qiang, H. Yang, L. Chen, H. Pang, Z. Ma, and W. D. Zhou, “Fano filters based on transferred silicon nanomembranes on plastic substrates”, Appl. Phys. Lett. Vol.93, 061106, 2008. Also selected at Virtual Journal of Nanoscale Science & Technology, Aug. 25, 2008.
  2. W.D. Zhou, Z. Ma, H. Yang, Z. Qiang, G. Qin, H. Pang, L. Chen, W. Yang, S. Chuwongin, and D. Zhao, “Flexible photonic-crystal Fano filters based on transferred semiconductor nanomembranes”, J. Phys. D. 42, 234007 (2009).
  3. L. Chen, H. Yang, Z. Qiang, H. Pang, L. Sun, Z. Ma, R. Pate, A. Stiff-Roberts, S. Gao, J. Xu, G. J. Brown, and W. D. Zhou, “Colloidal quantum dot absorption enhancement in flexible Fano filters”, Appl. Phys. Lett. Vol. 96, 083111 (2010).
  4. W. Yang, H. Yang, G. Qin, Z. Ma, J. Berggren, M. Hammar, R. Soref, and W. D. Zhou, “Large-area InP-based crystalline nanomembrane flexible photodetectors”, Appl. Phys. Lett. Vol. 96, 121107 (2010).
  5. W. Zhou, Z. Ma, S. Chuwongin, Y.-C. Shuai, J.-H. Seo, D. Zhao, H. Yang, and W. Yang, “Semiconductor nanomembranes for integrated silicon photonics and flexible Photonics (Invited)”, Opt. Quant. Electron. 44, 605 (2012), Special Issue on Photonic Integration, DOI 10.1007/s11082-012-9586-8, 2012.
  6. J. Hu, L. Li, H. Lin, P. Zhang, W. Zhou, and Z. Ma, “Flexible integrated photonics: where materials, mechanics and optics meet (Invited)”, Opt. Mater. Express, vol. 3(9), 1313-1331 (2013).
  7. L. Menon, H. Yang, Z. Ma, and W. Zhou, “Flexible three- color silicon membrane photodetector array”, IEEE Photon. J. 7, 1-6 (2015).
  8. J.-H. Seo, K. Zhang, M. Kim, D. Zhao, H. Yang, W. Zhou, and Z. Ma, “Flexible Phototransistors Based on Single-Crystalline Silicon Nanomembranes”, Advanced Optical Materials (DOI: 10.1002/adom.201500402). (Featured in Materials Views, Dec. 2015). (Cover Story) v.4(1), 120 (2016).
  9. L. Menon, H. Yang, S. J. Cho, S. Mikael, Z. Ma, C. Reuterskiöld-Hedlund, M. Hammar, and W. Zhou, “Heterogeneously Integrated InGaAs and Si Membrane Four Color Photodetector Arrays”, IEEE Photon. J. vol. 8(2), 6801907 (2016).
  10. S. Wang, Y. Liu, D. Zhao, H. Yang, W. Zhou, and Y. Sun, "Optofluidic Fano resonance photonic crystal refractometric sensors", Appl. Phys. Lett. 110, 091105 (2017). doi: http://dx.doi.org/10.1063/1.4977563
  11. Y. Liu, S. Wang, D. Zhao, W Zhou and Y. Sun, "High quality factor photonic crystal filter at k~0 and its application for refractive index sensing", Opt. Express 25(9), 10536 (2017).
  12. Y. Liu, W. Zhou, and Y. Sun, "Optical refractive index sensing based on high-Q bound states in the continuum in free-space coupled photonic crystal slabs", Special Issue on Silicon Technologies for Photonic Sensors, , Sensors 17, 1861 (2017).
  13. Y. Liu, S. Wang, P. Biswas, W. Zhou, and Y. Sun, “Optofluidic vapor sensing with free-space coupled 2D photonic crystal slabs”, Sci. Rep. vol. 9, 4209 (2019).
  14. W. Bai, H. Yang, Y. Ma, H. Chen, J. Shin, Y. Liu, Q. Yang, Z. Liu, S. Kang, W. Chen, X. Ge, X. Feng, P. Braun, Y. Huang, W. Zhou, and J. Rogers, “Flexible monocrystalline silicon transient optical waveguides and surface-wave biosensors”, Adv. Mater. 2018, 1801584. https://doi.org/10.1002/adma.201801584 (Cover Story)
  15. J. Shin, Z. Liu, W. Bai, Y. Liu, Y. Yan, Y. Xue, I. Kandela, M. Pezhouh, M. R. MacEwan, Y. Huang, W. Z. Ray, W. Zhou, and J. A. Rogers, "Bioresorbable optical sensor systems for monitoring of intracranial pressure and temperature," Science Advances, vol. 5, p. eaaw1899, 2019.
  16. W. Bai, J. Shin, R. Fu, I. Kandela, D. Lu, X. Ni, Y. Park, Z. Liu, T. Hang, D. Wu, Y. Liu, C. R. Haney, I. Stepien, Q. Yang, J. Zhao, K. R. Nandoliya, H. Zhang, X. Sheng, L. Yin, K. MacRenaris, A. Brikha, F. Aird, M. Pezhouh, J. Hornick, W. Zhou, and J. A. Rogers, "Bioresorbable photonic devices for the spectroscopic characterization of physiological status and neural activity," Nature Biomedical Engineering, vol. 3, pp. 644-654, 2019/08/01 2019.

Area III: Fano resonance photonic crystal membrane photonics

Zhou group and collaborators have been investigating various passive and active photonic and optoelectronic devices based on Fano resonance principles in photonic crystals, with a range of devices proposed and demonstrated with applications in three-dimensional integration photonics, free-space integrated photonics.

Fano resonance photonic crystal membrane photonics
  1. W. Zhou, D. Zhao, Y. Shuai, H. Yang, S. Chuwongin, A. Chadha, J.-H. Seo, K. Wang, V. Liu, Z. Ma, and S. Fan, “Progress in 2D photonic crystal Fano resonance photonics (Invited review)”, Prog. Quantum. Electron. 38, 1-74 (2014).
  2. W. Zhou and S. Fan (Ed.), “Photonic Crystal Metasurface Optoelectronics”, Vol. 100 in Semiconductors and Semimetals, Elsevier (2019), Hardcover ISBN: 9780128175422; eBook ISBN: 9780128175439.
IIIa: Ultra-high quality optical filters
  1. H. Yang, Z. Qiang, H. Pang, Z. Ma, and W. D. Zhou, “Surface-Normal Fano Filters Based on Transferred Silicon Nanomembranes on Glass Substrates”, Electron. Lett., vol. 44 (14), 858-9, 2008. Also highlighted and collected at http://kn.theiet.org/magazine/eletters/si-photonics.cfm
  2. Z. Qiang, H. Yang, L. Chen, H. Pang, Z. Ma, and W. D. Zhou, “Fano filters based on transferred silicon nanomembranes on plastic substrates”, Appl. Phys. Lett. Vol.93, 061106, 2008. Also selected at Virtual Journal of Nanoscale Science & Technology, Aug. 25, 2008.
  3. L. Chen, Z. Qiang, H. Yang, H. Pang, Z. Ma, and W. D. Zhou, “Polarization and angular dependent transmissions on transferred nanomembranes Fano filters”, Opt. Express, vol 17, 8396-8406, (2009).
  4. Y. Shuai, D. Zhao, Z. Tian, J.-H. Seo, R. B. Jacobson, D. Plant, M. Lagally, S. Fan, Z. Ma, and W.D. Zhou, “Double-layer Fano resonance photonic crystal filters”, Opt. Express, vol.21, 24582-9 (2013).
  5. Y. Shuai, D. Zhao, J. Seo, H. Yang, S. Fan, Z. Ma and W. Zhou, “Coupled double-layer Fano resonance photonic crystal filters with lattice-displacement”, Appl. Phys. Lett,. vol..103, 241106 (2013).
  6. Y. Shuai, D. Zhao, C. Stambaugh, N. Zimmerman, J. Lawall, and W. Zhou, “Coupled Bi-layer Photonic Crystal Slab Electro-optic Spatial Light Modulators”, IEEE Photon. J. 9, 7101411 (2017). DOI: 10.1109/JPHOT.2017.2675619 .
  7. S. Wang, Y. Liu, D. Zhao, H. Yang, W. Zhou, and Y. Sun, “Optofluidic Fano resonance photonic crystal refractometric sensors”, Appl. Phys. Lett. 110, 091105 (2017). doi: http://dx.doi.org/10.1063/1.4977563
  8. Y. Liu, S. Wang, D. Zhao, W Zhou and Y. Sun, “High quality factor photonic crystal filter at k ≈0 and its application for refractive index sensing”, Opt. Express 25(9), 10536 (2017).
  9. Y. Liu, W. Zhou, and Y. Sun, “Optical refractive index sensing based on high-Q bound states in the continuum in free-space coupled photonic crystal slabs”, Special Issue on Silicon Technologies for Photonic Sensors, , Sensors 17, 1861 (2017).
IIIb: Ultra-broadband single layer membrane reflectors
  1. H. Yang, S. Chuwongin, Z. Qiang, L. Chen, H. Pang, Z. Ma, and W. D. Zhou, “Resonance Control of Membrane Reflectors with Effective Index Engineering”, Appl. Phys. Lett. 95, 023110, (2009).
  2. Z. X. Qiang, H. Yang, S. Chuwongin, D. Zhao, Z. Ma, and W. D. Zhou, “Design of Fano broadband reflectors on SOI”, IEEE Photon. Technol. Lett. vol. 22(15), 1108 (2010).
  3. D. Zhao, Z. Ma and W.D. Zhou, “Field penetration and distribution in photonic crystal mirror cavities”, Opt. Express Vol. 18, Issue 13, pp. 14152-14158, 2010.
  4. D. Zhao, H. Yang, Z. Ma, and W. Zhou, "Polarization independent broadband reflectors based on cross-stacked gratings," Opt. Express 19, 9050-9055 (2011).
  5. H. Yang, D. Zhao, J.-H. Seo, S. Chuwongin, S. Kim, J. A. Rogers, Z. Ma, and W. Zhou, “Broadband Membrane Reflectors on Glass”, IEEE Photon. Technol. Lett. 24(6), 476-8, 2012.
  6. Y.-C. Shuai, D. Zhao, W. Yang, W. Zhou, J.-H. Seo, Z. Ma, G. Medhi, R. Peale, W. Buchwald and R. Soref, “Fano Resonance Membrane Reflectors from Mid-Infrared to Far-Infrared”, IEEE Photon. J. 5, (1) 2200106 (2013).
  7. A. Chadha, D. Zhao, S. Chuwongin, Z. Ma, and W. Zhou, “Polarization- and angle-dependent characteristics in two dimensional photonic crystal membrane reflectors”, Appl. Phys. Lett, vol..103, 211107 (2013).
  8. K. Balasundaram, P. K. Mohseni, Y. Shuai, D. Zhao, W. Zhou, and X. Li, “Photonic crystal membrane reflectors by magnetic field-guided metal-assisted chemical etching”, Appl. Phys. Lett. vol..103, 214103 (2013).
  9. S. Liu, D. Zhao, J.-H. Seo, Y. Liu, Z. Ma, and W. Zhou, “Athermal Photonic Crystal Membrane Reflectors on Diamond”, IEEE Photon. Technol. Lett. Vol. 27(10), 1072-5 (2015).
IIIc: Enhanced light-matter interactions for strong light absorption and emission
  1. L. Chen, H. Yang, Z. Qiang, H. Pang, L. Sun, Z. Ma, R. Pate, A. Stiff-Roberts, S. Gao, J. Xu, G. J. Brown, and W. D. Zhou, “Colloidal quantum dot absorption enhancement in flexible Fano filters”, Appl. Phys. Lett. Vol. 96, 083111 (2010).
  2. Y. Liu, A. Chadha, D. Zhao, J. R.Piper, Y. Jia, Y. Shuai, L. Menon, H. Yang, Z. Ma, S. Fan, F. Xia, and W. Zhou, “Approaching total absorption at near infrared in a large area monolayer graphene by critical coupling”, Appl. Phys. Lett. 105, 181105 (2014).
  3. X. Ge, M. Minkov, S. Fan, X. Li, and W. Zhou, "Laterally confined photonic crystal surface emitting laser based on monolayer tungsten disulfide operating at room temperature," arXiv preprint arXiv:1806.08019, 2018.

Research Overview:

Research Overview Diagram