Minimized thermal effects and strong two-photon absorption of aluminum, silver doped platinum bi-metal nanoparticles

• Published in: Optics and laser technology Vol. 160; p. 109032
• Main Authors: Rambabu, A., Sheetal, S., Akanksha, S., Balaji, Y., Venugopal Rao, S., Hamad, S., Krishna Podagatlapalli, G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2023
• Subjects: 2PA; Nanoparticles; Reverse saturable absorption; Saturable absorption; Surface plasmons; Thermo-optic effect; Nanoparticles; Reverse saturable absorption; Thermo-optic effect; Saturable absorption; 2PA; Surface plasmons
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2022.109032

[Display omitted] •NLO studies of Ag-Pt, and Al-Pt NPs with reduced thermo-optic effects were carried out for the first time.•NLO properties of Ag-Pt and Al-Pt NPs are due to the upshift in d band, and annihilation of excitons, respectively.•Alloying of Pt NPs reduces the thermo-optic effects and leads to pure electronic NLO properties. Herein, for the first time, we have investigated the strong nonlinear optical (NLO) properties aided with minimal thermo-optical effects in silver-platinum (Ag-Pt) nanoparticles (NPs) using Z-scan technique with high repetition rate femtosecond pulses at 700 nm. The NPs were synthesized using ultrafast laser ablation of Ag/Al targets immersed in the Pt colloidal solutions in isopropyl alcohol (IPA). We observed reverse saturable absorption (RSA)/two-photon absorption (2PA) behavior in Ag-Pt NPs (with 0.5 mM concentration of Pt), W-shaped switching behavior in Ag-Pt NPs (with 1 mM concentration of Pt), and RSA/2PA behavior in Ag-Pt NPs (with 3 mM concentration of Pt). The multiple-stage nonlinear absorption phenomenon is attributed to the interchange of pure 2PA or excited-state absorption, and 2PA saturation effects. Additionally, the broadband third-order NLO properties of aluminum-doped Pt (Al-Pt) bi-metallic NPs were obtained using spectral-dependent Z-scan studies at 700 nm, 800 nm, and 900 nm. The results revealed that Al-Pt bi-metallic NPs exhibited strong saturable absorption (SA), 2PA, and switching from SA to RSA. It is also revealed from the closed aperture Z-scan data that Ag-Pt and Al-Pt bi-metallic NPS exceed thermal contribution with strong 2PA coefficients unprecedentedfor single metal NPs. In the case of Ag-Pt NPs, strong 2PA saturation effects are attributed to the filling of Ag-O anti-bonding states by the photo-excited electrons and then charge transfer to the Pt plane. In the case of Al-Pt NPs, strong 2PA phenomena are ascribed to the enhancement of charge carriers in the conduction band and, hence, the strong surface plasmon resonances. The 2PA coefficients were evaluated to be ∼10−7 cm/W. The superior and switching NLO effects indicate that these materials might be utilized for potential applications, including optical modulators, and all-optical switching devices.