Substrates and interlayer coupling effects on Mo1-xWxSe2 alloys

Two-dimensional(2D) transition metal dichalcogenides alloys are potential materials in the application of photodetectors over a wide spectral range due to their composition-dependent bandgaps. The study of bandgap engineering is important for the application of 2D materials in devices. Here, we grow the Mo1-xWxSe2 alloys on mica, sapphire and SiO2/Si substrates by chemical vapor deposition(CVD) method. Mo1-x Wx Se2 alloys are grown on the mica substrates by CVD method for the first time. Photoluminescence(PL) spectroscopy is used to investigate the effects of substrates and interlayer coupling force on the optical bandgaps of as-grown Mo1-xWxSe2 alloys. We find that the substrates used in this work have an ignorable effect on the optical bandgaps of as-grown Mo1-xWxSe2. The interlayer coupling effect on the optical bandgaps of as-grown Mo1-xWxSe2 is larger than the substrates effect. These findings provide a new way for the future study of the growth and physical properties of 2D alloy materials.

Two-photon absorption towards pulse modulation in mechanically exfoliated and CVD monolayer cascaded MoS2 structures

Mechanical exfoliation(ME) and chemical vapor deposition(CVD) MoS2 monolayers have been extensively studied, but the large differences of nonlinear optical performance between them have never been clarified. Here,we prepared MoS2 monolayers using ME and CVD methods and investigated the two-photon absorption(TPA)response and its saturation. We found that the TPA coefficient of the ME monolayer was about(1.88 ± 0.21)× 10^3 cm/GW, nearly two times that of the CVD one at(1.04 ± 0.15)× 10^3 cm/GW. Furthermore,we simulated and compared the TPA-induced optical pulse modulation in multilayer cascaded structures, which is instructive and meaningful for the design of optical devices such as a beam shaper and optical limiter.

Facile synthesis of aqueous silver nanoparticles and silver/molybdenum disulfide nanocomposites and investigation of their nonlinear optical properties

Silver nanoparticle (AgNP) aqueous colloids with different surface plasmon resonance (SPR) frequencies were controllably synthesized by a facile and green chemical synthesis method. The obtained AgNPs with an average diameter of ~ 15 nm show a symmetrical SPR peak at ~ 400 nm. Another longitudinal SPR mode at ~ 520 nm occurs when increasing the amount of ethanol according to the ultraviolet-visible light spectra. The third-order nonlinear optical (NLO) absorption properties of the AgNP colloids were found to switch from two-photon absorption (TPA) to saturable absorption (SA) by tuning the SPR frequency using Z-scan technique with 340 fs pulses at 515 nm. When combined with two-dimensional (2D) MoS_(2), an enhanced SA response is observed for Ag/MoS_(2 )nanocomposites compared with the counterparts. The nonlinear absorption coefficient of Ag/MoS_(2) nanocomposites is about − (10.93 ± 0.6) × 10^(-2 )cm·GW^(−1), which is almost three times higher than that of MoS_(2). Our work has an instructive value in promoting the potential application of AgNPs and its nanocomposites in optoelectronic and photonic devices, such as optical limiting and ultrafast laser pulse generation.