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Mathematical optics involves studies into the various aspects of modern optics, including, among others, laser beam shaping, laser beam propagation and novel resonators. In studying the various aspects of modern optics both mathematics and physics are used.
- Laser beam shaping involves changing the actual shape of laser beam
- Laser beam propagation deals with the way in which the laser beam moves
- Novel resonators – A laser usually comprises an optical resonator this is where light can circulate (e.g. between two mirrors).
For the purposes of this segment, the focus will be on the CSIR’s mathematical optics research.
Optical tweezing is a popular topic globally, with many of the world's best laboratories working on it.
Everyone is familiar with the metal tweezers that we use at home to get splinters out of skin, or that doctors use when stitching up wounds. Well, laser light can also act as a tweezer. When you move the laser beam, it seems as if the light acts like a tweezer and the trapped particle moves with it. Since the particle can be controlled by just controlling the beam of light, we call this optical trapping and tweezing.
Today people are using optical tweezers to deliver drugs to individual cells, to manipulate cells in living cultures and even to control specific DNA strands inside cells using the laser beam in a complicated path and create novel laser beams that will allow things to be trapped without damaging them. One way to do this is through the use of modern optical elements in the form of digital holograms - like normal holograms but ‘digital’ rather than on film.
Optical turbulence
When a laser beam spreads through non-ideal conditions optical turbulence influences the propagation of laser beams. This has consequences for laser beams aimed at targets (e.g. in the defence sectors), as well as in telecommunications.
The CSIR’s mathematical optics team’s approach is to consider means of simulating atmospheric turbulence in the laboratory and finding means of addressing this problem. Thus far, they have made significant headway. See publications
Novel laser resonators
The team is involved in designing resonators with special modes that will extract maximum energy from the cavity, but with minimal thermal aberrations. A cavity resonator, usually used in reference to electromagnetic resonators, is one in which the waves exist in a hollow space inside the device.
This work has relevance to the design of high brightness solid-state lasers, where high energy in a good beam quality is required, as well as in the generation of high power flat-top beams for direct use in materials processing.
Optical vortices and vortex beams
An optical vortex is a beam of light the phase of which varies in a corkscrew-like manner along the beam's direction of propagation. On a flat surface, an optical vortex looks like a ring of light, with a dark hole in the centre.
Due to its self reconstruction ability vortex beams are used in optical tweezers. Vortex beams have also found applications in Quantum Entanglement.
Quantum physics deals with atomic and subatomic systems. It is a result of the discovery that waves have discrete energy packets (called quanta) that behave in a manner similar to particles.
Quantum entanglement is a vital resource in quantum information technology such as quantum computation and quantum cryptography. The idea is simply to entangle quantum states for secure information transfer, so that the cryptography is based on quantum physics and not man-made codes, which can be broken. Quantum cryptography makes use of quantum entanglement in the transmitting of information (a key) in quantum states. This communication system is able to detect 'eavesdropping'; it involves two communicating users who share information that can be used as a 'key' to encrypt and decrypt messages. Quantum cryptography is only used in producing and distributing the key.
However, challenges arise in using quantum states to carry data; for example, quantum noise and quantum decoherence are introduced in optical fibres resulting in the entanglement gradually being destroyed. Tackling this problem is the basis of the CSIR's research in this regard, conducted in collaboration with the University of KwaZulu-Natal.
Should the research project prove successful, it will have ground-breaking implications for the study of quantum cryptography.
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