Integrated optical vortices on a chip (w/ Video)

October 18, 2012
This is an illustration of an array consisting of three identical emitters. The three-dimensional emission pattern is calculated with the use of a dipole-emission–based semianalytical model. Credit: Miss Yue Zhang, based on data from authors of the paper.

An international research group led by scientists from the University of Bristol and the Universities of Glasgow (UK) and Sun Yat-sen and Fudan in China, have demonstrated integrated arrays of emitters of so call 'optical vortex beams' onto a silicon chip. The work is featured on the cover of the latest issue of Science magazine, published tomorrow.

Contradicting traditional conception, light in such beams does not propagate in straight rays. Instead, its energy travels in a spiral fashion in a hollow conical beam shape. The beams therefore look very much like a vortex or cyclone, with its 'twisted' either left-handed or right-handed. In theory, there is no limit to how twisted the light rays can be.

In , this feature is associated with the 'orbital angular momentum' (OAM) of photons – photons in such beams can be thought to orbit around the beam axis, somewhat similar to the movement of planets around the Sun or electrons around a nucleus.

When such light interacts with matter, it asserts a rotational force (a torque) on the matter; therefore it can be used as so called 'optical spanners' in addition to '', which can rotate as well as trap or droplets. Different degree of twist can also be used to transmit information – allowing more information to be carried by a single , and increasing the capacity of optical communications links.

The movie shows rotating spiral interference pattern created by disturbing the phase of a reference beam relative to that of a vortex beam with l=-4. The reference beam is a right hand circularly polarized Gaussian beam. Five arms can be seen clearly in the pattern. Credit: Xinlun Cai, Jianwei Wang, Mark G. Thompson, and Siyuan Yu

at the same frequency but with different OAM values can be used to transmit different streams information. Single particles of light (photons) can use these different degrees of twist to represent , where a single photon can be twisting both clock-wise and anti-clockwise at the same time. Applications are also being developed in using such light for imaging and sensing purposes. For example some molecules are chiral - they look the same under normal until illuminated by optical vortex beams with different degrees or directions of twist.

Conventionally the generation of such beams relied on bulk optical elements such as plates, lenses, and holograms. These are good for research but can be inconvenient for many applications, in particular where large numbers of such beams are needed at high packing density.

In contrast, the new emitters invented at Bristol are only a few micrometres in size and thousands of times smaller than conventional elements. They are based on silicon optical waveguides and can be made using standard integrated circuit fabrication technologies.

Siyuan Yu, Professor of Photonics Information Systems in the Photonics Research Group at the University of Bristol, who led the research, said: "Our microscopic optical vortex devices are so small and compact that silicon micro-chip containing thousands of emitters could be fabricated at very low costs and in high volume.

"Such integrated devices and systems could open up entirely new applications of optical vortex beams previously unattainable using bulk optics."

These devices are readily interconnected with each other to form complex and large arrays in photonic integrated circuits, and could be used for applications including communications, sensing and microscopic particle manipulation.

Dr Mark Thompson, Deputy Director of the Centre for Quantum Photonics at the University of Bristol, added: "Perhaps one of the most exciting applications is the control of twisted light at the single photon level, enabling us to exploit the quantum mechanical properties of optical vortices for future applications in quantum communications and quantum computation."

Explore further: Researchers create 'tornados' inside electron microscopes

More information: Integrated compact optical vortex beam emitters, Xinlun Cai, Jianwei Wang, Michael J. Strain, Benjamin Johnson-Morris, Jiangbo Zhu, Marc Sorel, Jeremy L. O'Brien, Mark G. Thompson, Siyuan Yu, Science, 19 October 2012.

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1 / 5 (1) Oct 18, 2012
This is related to the fixed point theorems.
This reminded me of this fixed point theorem:

Singularities vanish at zero.
Good news for physics abhorring quantum singularities.
5 / 5 (4) Oct 18, 2012
We will have optical computers long before quantum computers are common in households. But the benefits of optical computers will speed the development of the latter and not vice versa.
3 / 5 (2) Oct 19, 2012
This is related to the fixed point theorems.
This reminded me of this fixed point theorem:

Singularities vanish at zero.
Good news for physics abhorring quantum singularities.

Sorry, but I find this comment, well, pointless...
1 / 5 (1) Oct 19, 2012

The theory behind optical quantum vortices starts with topological quantum number stemming from the 'degree of a continuous mapping (used to prove a famous fixed point theory and "...the degree of a continuous map (for instance a map from space to some order parameter set) is one example of a topological quantum number..." - http://en.wikiped..._mapping

No one expects you to connect the dots to realize the point of my comment. And you don't see the point of this comment either.

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