Plasmon enhanced optical tweezers with gold-coated black silicon

TL;DR

This paper introduces a scalable, laser-processed gold-coated black silicon platform for plasmonic optical tweezers, enabling efficient, wavelength-dependent trapping of nanoparticles and biomolecules with potential for large-scale applications.

Contribution

It presents a novel, scalable fabrication method for plasmonic optical tweezers using laser-processed black silicon coated with gold, with detailed wavelength-dependent efficiency characterization.

Findings

Achieved trapping efficiencies comparable to state-of-the-art methods.

Demonstrated wavelength-dependent resonance effects on trapping efficiency.

Provided a scalable fabrication process for large-scale optical trapping applications.

Abstract

Plasmonic optical tweezers are a ubiquitous tool for the precise manipulation of nanoparticles and biomolecules at low photon flux, while femtosecond-laser optical tweezers can probe the nonlinear optical properties of the trapped species with applications in biological diagnostics. In order to adopt plasmonic optical tweezers in real-world applications, it is essential to develop large-scale fabrication processes without compromising the trapping efficiency. Here, we develop a novel platform for continuous wave (CW) and femtosecond plasmonic optical tweezers, based on gold-coated black silicon. In contrast with traditional lithographic methods, the fabrication method relies on simple, single-step, maskless tabletop laser processing of silicon in water that facilitates scalability. Gold-coated black silicon supports repeatable trapping efficiencies comparable to the highest ones reported to date. From a more fundamental aspect, a plasmon-mediated efficiency enhancement is a resonant effect, and therefore, dependent on the wavelength of the trapping beam. Surprisingly, a wavelength characterization of plasmon-enhanced trapping efficiencies has evaded the literature. Here, we exploit the repeatability of the recorded trapping efficiency, offered by the gold-coated black silicon platform, and perform a wavelength-dependent characterization of the trapping process, revealing the resonant character of the trapping efficiency maxima. Gold-coated black silicon is a promising platform for large-scale parallel trapping applications that will broaden the range of optical manipulation in nanoengineering, biology, and the study of collective biophotonic effects.