Second-Order Nonlinear Optical Properties of Monolayer Transition-Metal Dichalcogenides by Computational Analysis

Abstract

The second-order nonlinear optical properties of monolayer transition-metal dichalcogenides (TMDs) have been drawing increasing interest; yet, challenges remain in the measurements of the response. In this work, we report a first-principles analysis of the second-order nonlinear optical response of monolayer TMDs for transition metals from group V and VI. Our calculations of the second-order optical response for monolayer TMDs are useful for benchmarking, providing the intrinsic response, and for elucidation of trends in developing concepts for application. We analyzed the results by comparison with experimental measurements and previous computations, as available. We found that the second-order nonlinear optical properties of the monolayer TMDs are generally comparable in magnitude to other bulk materials currently in use in electro-optical devices. Given the magnitude of the second-order nonlinear optical properties and the two-dimensional nature of these materials, avenues are opening for reducing the size of electro-optical devices by using monolayer TMDs.

Angular Dependence of the Second-Order Nonlinear Optical Response in Janus Transition Metal Dichalcogenide Monolayers

“…The r yyy component of the Pockels coefficient of the Janus TMD monolayers is comparable to the r yyy component of monolayer TMDs. 24 We find a similar magnitude of 20 pm V over the calculated energy range in both cases, as well as a similar increase in the Pockels coefficient close Analysis of eqns 12 and 13 reveals that the angular dependence of the Pockels coefficient is different from the SHG nonlinear susceptibility because the 2θ terms dominate here, whereas 3θ terms dominate the SHG nonlinear susceptibility. As mentioned, the change in the angular dependence of the Pockels coefficient stems from the symmetry reduction introduced by the static electric field and thus the breaking of Kleinman symmetry.…”

“…The largest values of χ yyy (2) for the Janus TMD monolayers result from materials with the smallest bandgap energies and more parallel electronic bands, a trend that was also observed for TMD monolayers. 24 The electronic band structures of Janus TMD monolayers (Figure 2S) show nearly (anti) parallel bands between the M and K points, giving rise to the robust nonlinear optical response.…”

“…The unit cell volume (Ω) in periodic calculations is typically artificially large to reduce interactions between periodic images. We account for the increased unit cell volume by postprocessing all quantities that explicitly depend on Ω by replacing Ω = Ω mono → φΩ mono , where φ is the ratio of the bulk volume to that of the monolayer 24 summarized in Table 1S. In the case of Janus TMDs, the bulk volume is the average of the bulk volumes of the corresponding bulk TMDs 30 or calculated here, as necessary.…”

Facile Synthesis of Diversely Functionalized Peptoids, Spectroscopic Characterization, and DFT-Based Nonlinear Optical Exploration

“…18−20 Both linear and nonlinear responses have vital consideration for appropriate assessment of NLO properties. 21 Therefore, in the current study, we report the synthesis of novel peptoids (1−4) via Ugi four-component reaction and its NLO behavior exploration through DFT calculations.…”

“…The chemical building blocks encompassing NLO properties are extensively investigated for their implementation in optical communication, optical computing, dynamic image processing, and other areas of telecommunication and information technology. − The theoretical and experimental communities have paid much attention to explore NLO properties of novel systems owing to their blooming applications in surface interfaces, solid physics, materials, medicine, chemical dynamics, nuclear science, and biophysics. − The literature confirms the organic architectures for exhibiting eminent NLO response. − Due to supramolecular properties, organic compounds can provide more suitable frameworks than transition-metal organometallic frameworks because of several π-electrons in organic compounds . Since NLO response is generated by the entire electronic structure, complete study of molecular composition is essential to gain insight into NLO response of investigated compounds. − Both linear and nonlinear responses have vital consideration for appropriate assessment of NLO properties . Therefore, in the current study, we report the synthesis of novel peptoids ( 1–4 ) via Ugi four-component reaction and its NLO behavior exploration through DFT calculations.…”