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Towards high speed optical devices by exploiting the unique properties of 2D materials


Endowed with unique electronic and structural properties, 2D materials exhibit extraordinarily strong nonlinear and ultrafast responses to light. The variety of their electronic structures ranging from the gapless Dirac cone of graphene to variable band-gap materials such as Phosphorene and Transition Metal Di-Chalcogenides (TMDC) to the insulator Boron Nitride (BN) provides a broad spectrum of building blocks for optical devices. Together they hold great potential for the development of devices in which "light controls light" with superior speed, bandwidth and power consumption compared to hybrid systems requiring electro-optic mediation.This proposal will exploit various 2D -materials known to present exciting and unique photonic properties. The existence of robust excitons with large binding energies that derive from the reduced dielectric screening and large carrier masses, peculiar to 2D systems lead to uncommonly strong nonlinear responses. From the device perspective, this is aided by the absence of restrictions placed by phase matching in ultra-thin media. Moreover, we aim to develop optimized vertical hetero-structures built by combining well-chosen 2D materials to arrive at devices that exhibit properties not available in one-material 2D systems. For example, joining the TMDCs MoS2 and WS2 produces a heterostructure with offset bandgaps. This has been observed to encourage the rapid transfer of photo-excited holes from MoS2 into the valence band of WS2 leading to localized excitons that bridge their interface. By placing an insulating layer of h-BN between the two TMDCs, one can alter this electronic coupling and fine-tune the carrier transfer rates. Using a variety of nonlinear optical techniques such as time-delayed four-wave mixing, polarization gating and ultrafast pump-probe spectroscopy, we will explore the role of excitonic resonances and anisotropic relaxation mechanisms, as well as the physics of optically excited energy and electron transfer. Theoretical modeling of the electronic structure and carrier dynamics of the layered 2D structures will complement and guide the planned experimental work. These studies will provide fundamental information that will enable us to exploit the ultrafast dynamics and nonlinear optical response of these materials. The insight gained will facilitate the design of laboratory prototypes of 'all light' optical switches, modulators and saturable absorbers.One possibility, already under development in one of the participating groups, is a phosphorene based all- optical switch and modulator exploiting degenerate 4-wave mixing. Other devices contemplated are fast nonlinear absorbers exploiting exciton dynamical processes in which the rise-time and threshold intensity can be fine-tuned by combining layers to fabricate 2D hetero-structures. Ultrafast polarization switches using 2D materials with strong spin-orbit coupling is another option. (AU)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
GARCIA-BASABE, YUNIER; GORDO, VANESSA ORSI; DAMINELLI, LARA M.; MENDOZA, CESAR D.; VICENTIN, FLAVIO C.; MATUSALEM, FILIPE; ROCHA, ALEXANDRE R.; DE MATOS, CHRISTIANO J. S.; LARRUDE, DUNIESKYS G. Interfacial electronic coupling and band alignment of P3HT and exfoliated black phosphorous van der Waals heterojunctions. Applied Surface Science, v. 541, MAR 1 2021. Web of Science Citations: 0.
GIL-MOLINA, A.; CASTANEDA, J. A.; LONDONO-GIRALDO, D. F.; GABRIELLI, L. H.; CARDENAS, A. M.; FRAGNITO, H. L. High-order dispersion mapping of an optical fiber. Optics Express, v. 28, n. 3, p. 4258-4273, FEB 3 2020. Web of Science Citations: 0.
GARCIA-BASABE, YUNIER; PARRA, GUSTAVO G.; BARIONI, MARINA B.; MENDOZA, CESAR D.; VICENTIN, FLAVIO C.; LARRUDE, DUNIESKYS G. Species selective charge transfer dynamics in a P3HT/MoS2 van der Waals heterojunction: fluorescence lifetime microscopy and core hole clock spectroscopy approaches. Physical Chemistry Chemical Physics, v. 21, n. 42, p. 23521-23532, NOV 14 2019. Web of Science Citations: 0.

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