HERTFORDSHIRE, England, June 12, 2012 — Laser beams formed into dark helices, or corkscrews of light, have considerable advantages over their commonly considered bright cousins for applications such as lithography, particle trapping and particle transport, a theoretical investigation suggests.
“Dark helices are special because of their sharper intensity contrasts and, through my research, I have shown that they tend to outperform bright helices,” said Dr. Ole Steuernagel of the University of Hertfordshire’s Science and Technology Research Institute. “This is potentially important for lithographic applications to create sharply defined and contoured helical imprints.”
Illustration of a single bright helix (red line) superimposed on a single dark helix (black line). (Image: The University of Hertfordshire)
In lithography, light helices can create novel materials with helical imprints to provide left- or right-handed optically active materials. When applied in laser tweezers that manipulate particles through optical forces, helices can be used as a handedness filter for twisted molecules, create twisted waveguides for trapped quantum particles, or provide intertwined transport via intertwined optical helix configurations.
Although shaped similarly to their bright helix counterparts, dark helices are helically shaped threads of darkness embedded in a background of bright light. Dark helices are not resolution limited and provide better intensity contrast than bright ones. They also can be generated one by one and, most importantly, they can be arranged on a tight grid in a massively parallel fashion.
The dark helices could be most beneficial in a quantum-transport setting because their waveguides interact less with trapped particles than their bright counterparts. Because of this, dark helices are more suitable for sensitive quantum systems because they do less damage.
Steuernagel is hopeful that by showing that dark helices “can do” what bright helices will “not be able to do,” experimentalists will pick up his theoretical investigation.
The research appears today in Optics Express
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