Efficient ultrafast photoacoustic transduction on Tantalum thin films

TL;DR

This paper demonstrates that Tantalum thin films exhibit superior ultrafast photoacoustic transduction compared to Titanium, through experiments and simulations, with potential applications in generating modulated acoustic pulses for advanced photon sources.

Contribution

The study provides experimental and computational evidence that Tantalum outperforms Titanium in photoacoustic transduction efficiency in thin films, highlighting its potential for novel acoustic and photonic applications.

Findings

Tantalum exhibits higher photoacoustic transduction efficiency than Titanium.

Experimental results show clear Brillouin oscillations indicating effective strain generation.

Simulations confirm the experimental observations and explore acoustic pulse modulation possibilities.

Abstract

Nano-acoustic strain generation in thin metallic films via ultrafast laser excitation is widely used in material science, imaging and medical applications. Recently, it was shown that transition metals, such as Titanium, exhibit enhanced photoacoustic transduction properties compared to noble metals, such as Silver. This work presents experimental results and simulations that demonstrate that among transition metals Tantalum exhibits superior photoacoustic properties. Experiments of nano-acoustic strain generation by femtosecond laser pulses focused on thin Tantalum films deposited on Silicon substrates are presented. The nano-acoustic strains are measured via pump-probe transient reflectivity that captures the Brillouin oscillations produced by photon-phonon interactions. The observed Brillouin oscillations are correlated to the photoacoustic transduction efficiency of the Tantalum thin film and compared to the performance of Titanium thin films, clearly demonstrating the superior photoacoustic transduction efficiency of Tantalum. The findings are supported by computational results on the laser-induced strains and their propagation in these thin metal film/substrate systems using a Two-Temperature Model in combination with thermo-mechanical Finite Element Analysis. Finally, the role of the metal transducer-substrate acoustic impedance matching is discussed and the possibility to generate appropriately modulated acoustic pulse trains inside the crystalline substrate structures for the development of crystalline undulators used for {\gamma}-ray generation is presented.