Optical tweezers turn hybrid to trap lightly with ultra-low power

First demonstrated over 30 years ago, optical tweezers use beams of light to hold and manipulate microscopically small objects. As such, they allow scientists to better study living viruses, cancerous cells, bacteria and more. But there is one major drawback: they still have a relatively low trapping efficiency and therefore cannot hold these objects in place for long time while requiring relatively powerful light signals to do so.

Now, Donato Conteduca, a researcher at the Optoelectronics Laboratory at Politecnico di Bari, Italy, and his colleagues, in collaboration with a group at the University of York, report in APL Photonics of having created a novel approach that boosts this efficiency. Their design innovatively combines a dielectric photonic crystal nanobeam cavity with a plasmonic bowtie nanoantenna, in order to exploit advantages of high spectral and spatial energy confinement to strongly enhance light-matter interaction, and therefore increase the trapping efficiency.

For this study, the team designed and fabricated the hybrid cavity verifying that the experimental results matched the numerical ones predicted. They report that the hybrid cavity is able to trap particles of only 200 nanometers with a power that is only 190 microwatts and do so for over five minutes. This result confirms a remarkable improvement compared to the state-of-the-art of optical tweezers, in terms of strong efficiency and long trapping time with ultra-low power values.

According to Conteduca, the simulations they conducted demonstrate that this technique will also be able to trap biological matter that is smaller than 100 nanometers. Conteduca says that his group envisions that this technique can be applied to study proteins and viruses in the future, and to analyze the effects of several human diseases and improve their prevention.

Source: “Ultra-high Q/V hybrid cavity for strong light-matter interaction,” by Donato Conteduca, Christopher Reardon, Mark G. Scullion, Francesco Dell’Olio, Mario N. Armenise, Thomas F. Krauss, and Caterina Ciminelli, APL Photonics (2017). The article can be accessed at https://doi.org/10.1063/1.4994056 .