When you light a beam of light on your hand, you do not feel much, except a small amount of heat generated by the beam. When you light the same light in a world measured on the nano or micro scale, the light becomes a powerful manipulation tool that you can use to move objects around – securely attached to the light.
Researchers from the Structured Light group of Physics School at the University of the Witwatersrand in Johannesburg, South Africa, have found a way to use the full beam of the laser beam to control and manipulate small objects as single cells in a human body, small particles in small volume chemistry, or work with future on-chip devices.
While the specific technology, known as holographic optical capture and tweezing, is not new, Wits Researchers found a way to optimally utilize the full power of light – including vector light previously unavailable for this application. This forms the first vector holographic trap.
"Previously, holographic traps were limited to special light classes (scarlet), so it's very exciting that we can reveal a holistic entity that covers all classes of light, including the replication of all former capture units," Professor Andrew Forbes, Group Leader of the Cooperation and Distinguished Professor in the Physics School where he leads the Wits Structured Light Laboratory.
"What we have done is that we have shown the first vector holographic optical capture and tweezers system. The device allows to capture and manipulate only micrometric particles, such as biological cells, with light."
The final device can trap multiple particles at once and move them around just with vector states of light. The experiments for this study were conducted by Nkosi Bhebhe as part of his doctoral studies. The work is published in Natures online journal, Scientific reports.
In conventional optical capture and two -zing systems, the light is very tight in a small volume that contains small particles, such as biological cells. In this small scale (typically micro or nanometer), the forces that light can exert are significant, so particles can be caught by the light and then checked. When the light is moved, the particles will move. This idea won the American scientist Arthur Ashkin in 2018 the Nobel Prize in Physics. Originally, the light was mechanically controlled by steps and mirrors, but the tank was later improved by moving the light holographically, that is, using computer-generated holograms to control the light without moving parts and thereby control the particles. So far, only special classes of laser beams, called scalar beams, can be used in such holographic traps.
In their paper titled "A vector holographic optical trap", the Wits researchers showed how to create and control all patterns of light holographic and then used to form a new optical capture and two -zing device.
"In particular, the device can work with both the traditional laser beams (scalar beams) and more complex vector beams. Vector beams are very current and have found many applications, but no holographic trap for vector was so far possible," Forbes says.
Wits researchers demonstrate their new trap by holographically controlling both scales and vector beams in the same device, highlighting state-of-the-art and introducing a new device to society. The group expects the new device to be useful in controlled experiments in the micro and nanosphere, including single data studies in biology and medicine, small volume chemical reactions, basic physics and future on-chip devices.
Having shown that it is possible to create hundreds of customized light patterns from a hologram, research collects its previous work with holographic control of light using optical capture and tweezing.
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Nkosiphile Bhebhe et al. A vector holographical optical trap, Scientific reports (2018). DOI: 10,1038 / s41598-018-35889-0