The ability to design and enhance the nonlinear optical responses in two-dimensional (2D) transition-metal dichalcogenides (TMDCs) is both of fundamental interest and highly desirable for developing TMDC-based nonlinear optical applications, such as nonlinear convertors and optical modulators. Here, we report for the first time a strong anisotropic enhancement of optical second-harmonic generation (SHG) in monolayer molybdenum disulfide (MoS 2 ) by integrating with one-dimensional (1D) titanium dioxide nanowires (NWs). The SHG signal from the MoS 2 /NW hybrid structures is over 2 orders of magnitude stronger than that in the bare monolayer MoS 2 . Polarized SHG measurements revealed a giant anisotropy in SHG response of the MoS 2 /NW hybrid. The pattern of the anisotropic SHG depends highly on the stacking angle between the nanowire direction and the MoS 2 crystal orientation, which is attributed to the 1D NW-induced directional strain fields in the layered MoS 2 . A similar effect has also been observed in bilayer MoS 2 /NW hybrid structure, further proving the proposed scenario. This work provides an effective approach to selectively and directionally designing the nonlinear optical response of layered TMDCs, paving the way for developing high-performance, anisotropic nonlinear photonic nanodevices.
Ultrafast laser-processed MWNT/polymer composite materials for an absorbent polymeric matrix and self-assembly of PEDOT:PSS to obtain nanostructured electrically conductive hydrogels.
The
precise placement of semiconductor nanowires (NWs) into two-
or three-dimensional (2D/3D) micro-/nanoarchitectures is a key for
the construction of integrated functional devices. However, long-pending
challenges still exist in high-resolution 3D assembly of semiconductor
NWs. Here, we have achieved directional assembly of zinc oxide (ZnO)
NWs into nearly arbitrary 3D architectures with high spatial resolution
using two-photon polymerization. The NWs can regularly align in any
desired direction along the laser scanning pathway. Through theoretical
calculation and control experiments, we unveiled the laser-induced
assembly mechanism and found that the nonoptical forces are the dominant
factor leading to the directional assembly of ZnO NWs. A ZnO-NW-based
polarization-resolved UV photodetector of excellent photoresponsivity
was fabricated to demonstrate the potential application of the assembled
ZnO NWs. This work is expected to promote the research on NW-based
integrated devices such as photonic integrated circuits, sensors,
and metamaterial with unprecedented controllability of the NW’s
placement in three dimensions.
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