Science and Technology

Técnico Researchers found a way to generate light rays that whirl at high speeds

According to the team of physicists, whirling light rays make optical microscopes more powerful.

An international research team lead by researchers at Instituto Superior Técnico (IST, Portugal) and at Rutherford Appleton Laboratory (RAL, UK) found a way to generate light rays that whirl at high speeds.

This work, which represents a critical step forward on advanced optical manipulations, may influence the development of new generations of super-resolution microscopes for medical and scientific imaging. The discovery will be published in the issue of December 23rd of Physical Review Letters.

An optical vortex is an unusual light form, where the light rays rotate as they move, resembling a tornado, just as the whirling structures formed by draining water. Being not only mere scientific curiosity, optical vortex laser beams have an outstanding potential to revolutionise key technologies of our society. One of the most promising areas is related to optical microscopes with magnification powers that greatly exceed the actual limits.

The greater the rotation speed of the photons, which are the particles that compose light according to quantum mechanics, the larger is their magnification power. One of the challenges for the development of advanced microscopy techniques based on optical vortices resides in the difficulty of increasing their rotation speed independently of any other property. Showing that this could be achieved is an outstanding technological and scientific challenge.

The Portuguese research team, in collaboration with researchers from the Rutherford Appleton Laboratory and from the University of Oxford has now unravelled a solution to this question, which takes advantage from unusual optical properties of the plasma. The plasma, also known as the fourth state of matter, can be obtained when the temperature is so high that matter becomes ionised. Once turned into plasma, matter can change the propagation of light. The research team showed that the plasma is an ideal medium to produce light vortices that spin much faster than what had been possible to demonstrate.

According to Jorge Vieira, researcher from the Group for Lasers and Plasmas from the Institute for Plasmas and Nuclear Fusion at IST, “This work will allow to take full advantage from optical vortices for applications like super-resolution microscopy, and is the foundation for the design of very powerful optical microscopes” for several applications. The conclusions may be also easily transported to other scientific and technological topics such as optical communications, for instance in optical signal coding and decoding.