Photoacoustic model for laser-induced acoustic desorption of nanoparticles

TL;DR

This paper presents a theoretical model for laser-induced acoustic desorption of nanoparticles, enabling systematic optimization of laser parameters and substrate materials for compact, efficient LIAD systems suitable for practical applications.

Contribution

A novel theoretical framework based on the photoacoustic wave equation that guides the design and optimization of LIAD systems, improving upon empirical methods.

Findings

Model accurately predicts acoustic wave generation and propagation.

Compact laser systems with sub-nanosecond pulses can match laboratory performance.

Material optimization suggests alternatives to aluminum substrates.

Abstract

Laser-induced acoustic desorption (LIAD) enables loading nanoparticles into optical traps under vacuum for levitated optomechanics experiments. Current LIAD systems rely on empirical optimization using available laboratory lasers rather than systematic theoretical design, resulting in large systems incompatible with portable or space-based applications. We develop a theoretical framework using the photoacoustic wave equation to model acoustic wave generation and propagation in metal substrates, enabling systematic optimization of laser parameters. The model identifies key scaling relationships: surface acceleration scales as $\tau^{-2}$ with pulse duration, while acoustic diffraction sets fundamental limits on optimal spot size $w \gtrsim \sqrt{v\tau d}$. Material figures of merit combine thermal expansion and optical absorption properties, suggesting alternatives to traditional aluminum substrates. The framework validates well against experimental data and demonstrates that compact laser systems with sub-nanosecond pulse durations can achieve performance competitive with existing laboratory-scale implementations despite orders-of-magnitude lower pulse energies. This enables rational design of minimal LIAD systems for practical applications.