Nonlinear photoacoustic response of suspensions of laser-synthesized plasmonic titanium nitride nanoparticles

A nonlinear photoacoustic (PA) response from solutions of 40 nm plasmonic titanium nitride nanoparticles (NPs) synthesized by laser ablation in a liquid environment (acetone) is reported. Using a photoacoustic Z-scan with 5 ns pumping pulses, values of effective nonlinear absorption (NLA) coefficients (beta PA,eff) were measured and found to be 3.2710.17 x 10(-8), 6.4110.32 x 10(-8), and 3.2210.16 x 10(-8) for 600, 700, and 800 nm pumping wavelengths, respectively. To take into account the influence of nonlinear scattering, absorption-dependent PA measurements were carried out together with the optical Z-scan, and the obtained data were compared. The origin of the effective absorptive nonlinearity is discussed based on combined NLA in NPs, nonlinear scattering, and bubble generation triggered by NP-mediated light absorption. Potential applications include biomedical diagnostics and therapy. (C) 2020 Optical Society of America