Amplitude-modulated acoustic waves by nonlinear optical signals in bimetallic Au-Pt nanoparticles and ethanol based nanofluids

Acoustic waves were propagated through bimetallic Gold and Platinum nanoparticles suspended in ethanol in order to analyze their modification in amplitude by the assistance of third-order nonlinear optical effects. Nanosecond pulses at 532 nm wavelength were able to modify the acoustic transmittance by shifting the resonance of the mechanical vibration modes of the sample contained in a quartz cuvette. The optical Kerr effect exhibited by the nanoparticles was identified to be responsible for third-order optical nonlinearities that caused important changes in density associated with the sample. The nanofluids were prepared by a sol-gel method and explored by a vectorial two-wave mixing experiment. The nanostructured nature of the samples was evaluated by standard UV-Vis spectroscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy measurements. Potential applications for developing optomechanic nanosystems sensitive to pressure driven by optical nonlinearities can be contemplated.