Nonlinear Optical Properties of 2D CdSe Nanoplatelets in a Nonresonant Regime

Abstract

The nonlinear optical response of CdSe and CdSe/CdS core/shell nanoplatelets (NPLs) in toluene suspension was determined by using Z-scan and optical Kerr gate (OKG) techniques at 800 nm in the femtosecond regime. First, an analysis of the nonlinearities based on the Z-scan resulted in n 2 = 1.4 × 10 −16 cm 2 /W and n 2 = 1.3 × 10 −16 cm 2 /W for CdSe and CdSe/CdS core/shell NPLs, respectively. Fifth-order nonlinear absorption behavior was predominant, resulting in α 4 = 4.0 × 10 −2 cm/GW for CdSe NPLs and α 4 = 9.0 × 10 −3 cm/GW for CdSe/CdS core/shell NPLs for an optical intensity of 60.97 and 122 GW/cm 2 , respectively. The nonlinear refractive index obtained from Z-scan is in good agreement with those obtained from the OKG, and the response time obtained from OKG showed a decay of less than 1 ps for all studied materials, about 5 times slower than the pulse duration. For optical intensities in the range between 30.45 and 182.8 GW/cm 2 , NLA was not observed for toluene but was observed for CdSe and CdSe/CdS core/shell NPLs, revealing that the presence of the NPLs decreases the threshold of the absorptive nonlinearity. The results are discussed and explained based on the well-known materials' electronic structure.Article pubs.acs.org/JPCC

Effect of particle size on optical and electrical properties of thin films – a simulation approach

“…There are endless reports of determination of optical properties of different materials developed through different physical deposition techniques in thin film form. For instances, in the year 2023 only:-Vijay et al investigated the impact of annealing temperature on the microstructure, defects, and optical properties of ZnO thin films using a sol-gel-based spin coating method and showed that particle size increases with annealing temperature, and the optical band gap reduces [22]; Banerjee et al investigated the origin of visible emissions in ZnO, focusing on excitation wavelength-dependent tuneable emission [23]; Orek et al studied the electrical, optical, and structural properties of a wurtzite-like zinc oxide nanostructure, examining the influence of quantum confinement on optical characteristics [24]; Sarmh and Borah studied nanocrystalline CdSe thin films, finding them suitable for optoelectronic devices with defect-controlled photocurrents and a doubly activated transport mechanism [25]; Gonçalves et al studied the nonlinear optical response of CdSe, revealing a predominant fifth-order nonlinear absorption behaviour and a nonlinear refractive index in good agreement with the OKG [26]; Kafashan et al investigated the impact of Cu-doping on Cadmium selenide (CdSe), highlighting its potential applications in optoelectronics due to improved absorbance, reflectance, and band gap [27].…”