(439f) Nanoantenna Enhanced Wavelength Mixing in Monolayer Transition Metal Dichalcogenide

Nanoantenna enhanced wavelength mixing in monolayer
transition metal dichalcogenide

D. Keith Roper^a,b*_, Greg Forcherio^c, Mourad Benamara^d,
Luigi Bonacina^e

^a
Microelectronics
and Photonics Graduate Program, University of Arkansas, Fayetteville, AR
72701        

^b Department of Chemical
Engineering, University of Arkansas, Fayetteville, AR 72701

^cArmy Research Laboratory, Adelphi, MD 20783

^dInstitute for Nanoscience and
Engineering, University of Arkansas, Fayetteville, AR 72701

^e GAP-Biophotonics,
Université de Genève, Genève, CH 1211

     Monolayer
(1L) transition metal dichalcogenide (TMD) crystals offer compelling new
functionalities, e.g., gate tunability of p-n junction, valleytronics and
anti-ambipolarity as well as unique optical, electronic and transport
properties attributable to distinct atom-scale heterointerfaces. These features
could enable atomically-thin flexible integrated circuits, field effect
transistors and closed-loop resonators. However, present utility of 2D
semiconductors is limited by difficulty
in tuning their optoelectronic properties.

    
This work compared wavelength mixing at heterointerfaces of 1LTMD exhibiting
broken inversion symmetry with and without an adjacent resonant nanoantenna
(NA). Heterostructures of 1LTMD and NA were self-assembled via exfoliation and
dropcasting. Nanometer- and femtosecond-resolved electron energy loss
spectroscopy (EELS) was used to simulate and measure low-energy NA plasmon
modes, damping and electric near fields at heterointerfaces. Discrete dipole
approximation (DDA) was used to predict and induce bright, dark, and hybrid modes,
damping, and electromagnetic near fields (Fig. 1). EELS allowed quantitative femtosecond-scale
measurement of spectroscopic plasmon dephasing and nanometer-resolved mapping
of electric fields on the NA and 2DNC-NA hybrids.  A tunable laser scanning confocal microscope (LSCM)
was used to measure wavelength mixing of NA, TMD and TMD-NA heterostructures
(Fig. 2). Hyper Rayleigh Scattering (HRS) was used to measured second order
nonlinear coefficient of NA-1LTMD. From HRS and LSCM data, values of second
harmonic efficiency were compared for TMD and TMD-NA heterostructures.  A
computational scaffold supporting analysis spanning atom to nanometer scales
was used to develop compact structure-function relations in order to
rationalize measured values.      

    
Coordination of DDA, EELS, LSCM and HRS supports
comprehensive characterization of wavelength mixing in 1LTMD and 1LTMD-NA heterostructures
at high spatiotemporal resolution.

 [1] G.T. Forcherio and D.K. Roper et al., in preparation.