Polarity Change of Nonlinear Absorption between Monolayer and Bilayer/Multilayer

POSTER

Abstract

The monolayer of TMDC has a direct bandgap which is wider than the indirect bandgap of the bilayer/multilayer. The bandgap can be modified based on the number of layers and the temperature. The change of bandgap plays an important role in the nonlinear absorption process which can be illustrated through the Jablonski diagrams. Two-step absorption with one photon for each step, two-photon absorption to the real final state through a virtual intermediate state, and two-photon excitation to the virtual final state through a virtual intermediate state are all included in the nonlinear absorption process. The allowed electric dipole transition $\left| \right.i\left. \right\rangle \to \left| \right.f \left. \right\rangle $between the two states in the one-photon excitation is due to different parities. Saturable (negative) absorption (SA) occurs when the ground-state absorption cross-section is higher than the excited-state absorption cross-section, $\sigma_{g} >\sigma_{e} $. Alternatively, the allowed electric dipole transitions $\left| \right.i\left. \right\rangle \to \left| \right.m\left. \right\rangle $and $\left| \right.m\left. \right\rangle \to \left| \right.f \left. \right\rangle $between the initial and final states in the two-photon excitation are due to the same parities. The reverse saturable (positive) absorption (RSA) becomes dominant when the excited state absorption cross-section is higher than the ground-state absorption cross-section, $\sigma_{e} >\sigma_{g} $. Atomic layers that show SA are utilized for laser Q-switching and mode-locking, while the atomic layers which demonstrate RSA are utilized for optical power limiting. Acknowledgements: This work at HU is supported by NSF HRD-1137747, ARO W911NF-15-1-0535, and NASA NNX15AQ03A.

Authors

  • Tikaram Neupane

    Hampton University

  • Quinton Rice

    Hampton University

  • Jonathan Tan

    Duquesne University, Baker Hughes, Hampton University, Korea Research Institute of Standards and Science, Electronics and Telecommunications Research Institute, Texas Christian University, University of North Texas Health Science Center, Austin Peay State University, Virginia Military Institute, Pennsylvania State University, University of Virginia, Washington University, National Institute for Materials Science, Japan, Tokyo Metropolitan University, Japan, Univ of Kentucky, Argonne National Laboratory, Oak Ridge National Laboratory, Univ of Virginia, James Madison University, Department of Chemistry & Biochemistry, High Point University, Department of Chemistry, High Point University, Department of Physics, James Madison University, Department of Physics & Astronomy, Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, Institute of Renewable Energy and Environment Technology, University of Bolton, Bolton, UK, Division of Materials Science and Engineering, Ames Laboratory, US Dept. of Energy, Ames, IA, Lehigh University, University of Pardubice, Universite de Rennes, Jan Dlugosz University, Translume, NSCL/FRIB, Duke University, University of Massachusetts - Amherst, University of St. Andrews, National Radio Astronomy Observatory, University of Florida, Yale University, None, Georgia College & State Univ, Georgia College & State University, National University of Sciences and Technology (NUST), Univ of Tennessee Space Inst, The University of Virginia, Chiang Mai University, DHA Suffa University, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic, Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN, United States, George Mason University, Northern Virginia Community College, Department of Physics, University of Virginia, Istanbul University, Georgia College and State University, University of Houston, Western Kentucky Univ, James Madison University, Virginia Polytechnic Institute and State University, Pontifica Universidad Catolica de Chile, Trent University, Univ of Arizona, Ohio State University, NRAO, University of Virginia/NRAO

  • Jonathan Tan

    Duquesne University, Baker Hughes, Hampton University, Korea Research Institute of Standards and Science, Electronics and Telecommunications Research Institute, Texas Christian University, University of North Texas Health Science Center, Austin Peay State University, Virginia Military Institute, Pennsylvania State University, University of Virginia, Washington University, National Institute for Materials Science, Japan, Tokyo Metropolitan University, Japan, Univ of Kentucky, Argonne National Laboratory, Oak Ridge National Laboratory, Univ of Virginia, James Madison University, Department of Chemistry & Biochemistry, High Point University, Department of Chemistry, High Point University, Department of Physics, James Madison University, Department of Physics & Astronomy, Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, Institute of Renewable Energy and Environment Technology, University of Bolton, Bolton, UK, Division of Materials Science and Engineering, Ames Laboratory, US Dept. of Energy, Ames, IA, Lehigh University, University of Pardubice, Universite de Rennes, Jan Dlugosz University, Translume, NSCL/FRIB, Duke University, University of Massachusetts - Amherst, University of St. Andrews, National Radio Astronomy Observatory, University of Florida, Yale University, None, Georgia College & State Univ, Georgia College & State University, National University of Sciences and Technology (NUST), Univ of Tennessee Space Inst, The University of Virginia, Chiang Mai University, DHA Suffa University, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic, Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN, United States, George Mason University, Northern Virginia Community College, Department of Physics, University of Virginia, Istanbul University, Georgia College and State University, University of Houston, Western Kentucky Univ, James Madison University, Virginia Polytechnic Institute and State University, Pontifica Universidad Catolica de Chile, Trent University, Univ of Arizona, Ohio State University, NRAO, University of Virginia/NRAO

  • Jonathan Tan

    Duquesne University, Baker Hughes, Hampton University, Korea Research Institute of Standards and Science, Electronics and Telecommunications Research Institute, Texas Christian University, University of North Texas Health Science Center, Austin Peay State University, Virginia Military Institute, Pennsylvania State University, University of Virginia, Washington University, National Institute for Materials Science, Japan, Tokyo Metropolitan University, Japan, Univ of Kentucky, Argonne National Laboratory, Oak Ridge National Laboratory, Univ of Virginia, James Madison University, Department of Chemistry & Biochemistry, High Point University, Department of Chemistry, High Point University, Department of Physics, James Madison University, Department of Physics & Astronomy, Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, Institute of Renewable Energy and Environment Technology, University of Bolton, Bolton, UK, Division of Materials Science and Engineering, Ames Laboratory, US Dept. of Energy, Ames, IA, Lehigh University, University of Pardubice, Universite de Rennes, Jan Dlugosz University, Translume, NSCL/FRIB, Duke University, University of Massachusetts - Amherst, University of St. Andrews, National Radio Astronomy Observatory, University of Florida, Yale University, None, Georgia College & State Univ, Georgia College & State University, National University of Sciences and Technology (NUST), Univ of Tennessee Space Inst, The University of Virginia, Chiang Mai University, DHA Suffa University, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic, Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN, United States, George Mason University, Northern Virginia Community College, Department of Physics, University of Virginia, Istanbul University, Georgia College and State University, University of Houston, Western Kentucky Univ, James Madison University, Virginia Polytechnic Institute and State University, Pontifica Universidad Catolica de Chile, Trent University, Univ of Arizona, Ohio State University, NRAO, University of Virginia/NRAO