Structuring Nonlinear Wavefront Emitted from Monolayer Transition-Metal Dichalcogenides

Abstract

<jats:p>The growing demand for tailored nonlinearity calls for a structure with unusual phase discontinuity that allows the realization of nonlinear optical chirality, holographic imaging, and nonlinear wavefront control. Transition-metal dichalcogenide (TMDC) monolayers offer giant optical nonlinearity within a few-angstrom thickness, but limitations in optical absorption and domain size impose restriction on wavefront control of nonlinear emissions using classical light sources. In contrast, noble metal-based plasmonic nanosieves support giant field enhancements and precise nonlinear phase control, with hundred-nanometer pixel-level resolution; however, they suffer from intrinsically weak nonlinear susceptibility. Here, we report a multifunctional nonlinear interface by integrating TMDC monolayers with plasmonic nanosieves, yielding drastically different nonlinear functionalities that cannot be accessed by either constituent. Such a hybrid nonlinear interface allows second-harmonic (SH) orbital angular momentum (OAM) generation, beam steering, versatile polarization control, and holograms, with an effective SH nonlinearity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:msup><mml:mrow><mml:mi>χ</mml:mi></mml:mrow><mml:mrow><mml:mfenced open="(" close=")"><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:mfenced></mml:mrow></mml:msup></mml:math> of ~25 nm/V. This designer platform synergizes the TMDC monolayer and plasmonic nanosieves to empower tunable geometric phases and large field enhancement, paving the way toward multifunctional and ultracompact nonlinear optical devices.</jats:p>

Engineering photonic environments for two-dimensional materials

“…The sign of the circular polarization of the SHG signal originates from the socalled nonlinear selection rule [224,225]. A similar work was reported shortly after [226]. The coupling strength between the integrated WS 2 monolayer with the plasmonic metasurface, which is similar to the structure of Figure 5D, can reach to the strong coupling regime, leading to the observation of spin-selective excitation of directional flows of polaritons [127].…”

Nonlinear Transition-Metal-Dichalcogenide Metasurfaces

“…The cross symbol in table I refers to the lack of SHG/THG measurement or no SHG/THG in those references. We note that while the nonlinear emission from monolayer TMDCs coupled to plasmonic 58,59 or dielectric metasurfaces 60 have also been recently studied, our TMDC metasurface offers several fundamental advantages. These include the ability to simultaneously enhance the SHG and THG processes, offering a significantly higher interaction volume for the THG.…”

Recent advances in multi-dimensional metasurfaces holographic technologies

“…Apart from light modulation in linear optics, metasurfaces have gradually shown their great potential of tailoring the wavefront in nonlinear optical regimes. Numerous methods have been proposed for achieving nonlinear wavefront control such as harmonic generation [18], nonlinear imaging [102,103], nonlinear beam shaping [42,[104][105][106] and holography [19,100,101,[107][108][109] in recent years.…”

“…An enhancement of the SHG by one order of magnitude is achieved owing to large plasmonic field localization around the nanoholes of Au metasurface. Then the proposed design strategy is extended to realize more complicated nonlinear wavefront functionalities such as second-harmonic (SH) OAM generation, versatile polarization control and holograms [109].…”