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Kannatassen (Krishen) Appavoo

Goldhaber Post-Doctoral Fellow | Advanced Optical Spectroscopy and Microscopy


  • Ultrafast spectroscopy
  • High-resolution electron-beam lithography
  • Plasmonics and Metamaterials
  • Phase transition in strongly correlated materials
  • Hybrid Organic-Inorganic Photovoltaics
  • Water-splitting Heterostructured Photocatalysts
  • Pulsed laser deposition
  • 3D Finite-difference Time-domain Electromagnetic Simulations

CFN Research Activities

My research focuses on understanding light-matter interactions at its fundamental nanometer- length (1e-9 m) and femtosecond-time (1e-15 s) scales. Using advanced optical spectroscopy, I study how changes in size, crystallinity, morphology and heterostructuring affect the dynamics of nanostructures.  Understanding these dynamical processes - which represent fundamental limits to device efficiency - provide insights into designing next-generation nanostructured systems for solar water-splitting photocatalysis, photovoltaics and optoelectronic technologies



  • B.As.: Berea College (2008) [Major: Physics and Mathematics Minor: Computer Science]
  • PhD: Vanderbilt University (2012)
    • Interdisciplinary Materials Science / Applied Optical Physics

    • Dissertation Title: Hybrid Phase-Changing Nanostructures: From Reconfigurable Plasmonic Devices to Ultrafast Dynamics

Professional Appointments

  • Goldhaber Distinguished Postdoctoral Fellow: Brookhaven National Laboratory

    • Center for Functional Nanomaterials

    • Project: Characterizing novel hybrid nanostructures, using in situ optical and electrical measurements, for light-harvesting applications. My project includes developing broadband optical probes for studying ultrafast dynamics ‑ like electron-hole separation, carrier-carrier interaction and electron-phonon coupling - and energy transfer mechanisms in nanostructured systems

Selected Publications & Research Highlights

Appavoo K, Liu M, Black CT, Sfeir MY.
Quantifying bulk and surface recombination processes in nanostructured water splitting photocatalysts via in situ ultrafast spectroscopy.
Nano Letters 2015. Jan 7;15(2): 1076-1082

Lei DY, Appavoo K, Ligmajer F, Sonnefraud Y, Haglund RF and S.A. Maier.
Optically-Triggered Nanoscale Memory Effect in a Hybrid Plasmonic-Phase Changing Nanostructure.
ACS Photonics 2015 2 (9), 1306 

Appavoo K, Liu X, Menon VM, Sfeir MY.
Room-Temperature Exciton Lasing in Ultrathin Film of Coupled Nanocrystals.
Postdeadline CLEO Science and Innovations OSA 2015, JTh5B

Zeng C, Chen Y, Kirschbaum K, Appavoo K, Sfeir MY, Li T, Rosi N and Jin R.
Ordering at all scales in the non-metallic 133-gold-atom nanoparticle.
Science Advances 2015. 1(2)

Appavoo K, Wang B, Brady N, Seo M, Nag J, Pantelides ST, Prasankumar RP, Hilton DJ, Haglund RF.
Ultrafast phase transition via catastrophic phonon collapse driven by plasmonic hot-electron injection.
Nano Letters 2014 Mar 12;14(3)

Appavoo K and Haglund RF.
Polarization selective phase-change nanomodulator.
Nature Scientific Reports 2014 Oct 27; 4:6771

Appavoo K and Sfeir MY.
Enhanced broadband ultrafast detection of ultraviolet emission using optical Kerr gating.
Rev. Sci. Instrum. 2014 May;85(5) [Cover Art]

Appavoo K, Liu M, Sfeir MY.
Role of size and defects in ultrafast broadband emission dynamics of ZnO nanostructures.
Appl. Phys. Lett. 2014 Feb 28;104 (13)

Wall S, Wegkamp D, Foglia L, Appavoo K, Nag J, Haglund RF Jr, Stähler J, Wolf M.
Ultrafast changes in lattice symmetry probed by coherent phonons.
Nature Communications 2012 Mar 6;3:721

Appavoo K, Lei DY, Sonnefraud Y, Wang B, Pantelides ST, Maier SA, Haglund RF.
Role of defects in the phase transition of VO2 nanoparticles probed by plasmon resonance spectroscopy.
Nano Letters 2012 Feb 8;12(2)

Appavoo K and Haglund RF.
Detecting nanoscale size dependence in VO2 phase transition using a split-ring resonator metamaterials.
Nano Letters 2011 Mar 9;11(3)