Scientists at TMOS, the ARC Centre of Excellence for Transformative Meta-Optical Systems, have made a significant advancement toward creating metasurface-enabled tractor beams, or light beams that can attract particles.
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In a study recently published in ACS Photonics, a team of researchers from the University of Melbourne have successfully created a solenoid beam using a silicon metasurface.
Traditionally, solenoid beams have been generated with bulky special light modulators (SLMs), which can be impractical for handheld devices due to their larger size and heavier weight. The new metasurface, however, is a nanopatterned silicon layer only about 1/2000 of a millimeter thick.
The researchers hope that this metasurface could be used in several future applications, such as non-invasive biopsies, which would help protect tissue from the trauma typically caused by current methods like forceps.
Generally, light beams exert a pushing force, moving particles away from the source. Solenoid beams, on the other hand, draw particles toward the light source, functioning similarly to how a drill pulls wood shavings up the bit.
This newly developed solenoid beam offers several advantages over previous versions. It allows for more flexible input beam conditions, eliminates the need for an SLM, and has significantly lower size, weight, and power requirements.
The metasurface was crafted by mapping the phase hologram of the desired beam to create a pattern. Silicon was then fabricated using electron beam lithography and reactive ion etching. When an input beam, such as a Gaussian beam, passes through the metasurface, around 76 % of it is converted into a solenoid beam, which bends away from the unconverted beam, enabling unobstructed research. The team successfully characterized the beam at a distance of 21 centimeters.
The compact size and high efficiency of this device could lead to innovative applications in the future. The ability to pull particles using a metasurface might have the potential to impact the field of biopsy by potentially reducing pain through less invasive methods. We are excited to investigate the performance of our device in particle manipulation, which could offer valuable insights.
Maryam Setareh, Lead Researcher, Department of Electrical and Electronic Engineering, University of Melbourne
Chief Investigator Ken Crozier said, “The next stage of this research will be to experimentally demonstrate the beam’s ability to pull particles, and we will be excited to share those results when they are available. This work opens new possibilities for using light to exert forces on tiny objects.”
Journal Reference:
Setareh, M., et al. (2024) High-Efficiency Triple-Helix Solenoid Beam Generated by Dielectric Metasurface. ACS Photonics. doi.org/10.1021/acsphotonics.4c00874.