Enhancing saturable absorption in a Au-decorated MoS2/PEDOT:PSS nanocomposite through plasmon resonance and Pauli blocking

Abstract

We have effectively demonstrated a technique for substantial alteration of the nonlinear saturable absorption (SA) properties in nanocomposite films (NCF) composed of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) and molybdenum disulfide (MoS₂) decorated with gold nanoparticles (AuNPs). This control is achieved by adjusting the AuNP concentration on the MoS₂ surface and varying the input pulse energy of the laser. The simple drop-casting method is used to create the nanocomposite films (NCFs) on a glass substrate with different amounts of Au-decorated MoS₂. The Kramers–Kronig equations are employed for determining the refractive index and extinction coefficient values of the resulting NCFs. Nonlinear investigations reveal that adding Au-decorated MoS₂ to pure PEDOT:PSS alters its optical nonlinearity. Surface plasmon resonance and Pauli blocking have been observed in Au-decorated MoS₂/PEDOT:PSS NCFs. This increases NCF's saturable absorption. An open aperture Z-scan method is utilized to study nonlinear optics, with excitation achieved using a nanosecond (ns) pulsed laser operating at a 532 nm wavelength. The findings reveal the noteworthy saturable absorption characteristics of the NCFs.