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Linköping University - Quantum dots provide complete control of photons

DCN Corp® - Two ways of creating polarised light with the right hand side emitted via Quantum dots (QD). Credit - Dr Fredrik Karlsson, Linköping University (LU), SwedenEmitting photons at the top of a micro-pyramid Quantum dot (QD), researchers at Linköping University (LU) have managed to create a polarised light source for such things as energy saving computer screens and wire-tap proof communications

Polarised light (light waves oscillating on the same plane) forms the foundation for technology, such as Liquid Crystal Display (LCD) displays in computers and/or TV sets, and advanced quantum encryption. Typically this is created by normal unpolarised light passing through a filter that blocks the unwanted light waves. At least half of the light emitted and thereby an equal amount of energy is lost in the process.

A better process is to emit light that is polarised right at the source, and this can be accomplished with QDs. QDs are described as crystals of semiconductive material so miniature that they produce quantum mechanical phenomena. However, until recently they have only achieved polarisation that is either entirely too weak and/or hard to control.

A research group led by Professor Per Olof Holtz specialising in semiconductive materials is presenting an alternative method where asymmetrical QD of a nitride (Mg3N2) material with Indium (In) is formed at the top of microscopic six-sided pyramids. Such QDs have succeeded in creating light with a high degree of linear polarisation with an average of 84%. The results were published in the Nature periodical Light: Science & Applications.

Professor Holtz lead researcher stated - "We're demonstrating a new way to generate polarised light directly, with a predetermined polarisation vector and with a degree of polarisation substantially higher than with the methods previously launched."

In experiments, QDs were employed that emit violet light at a wavelength of 415 nm, but the photons can in principle take on any colour at all within the visible spectrum through varying the amount of the metal In.

As stated by an author of the article, Fredrik Karlsson - "Our theoretical calculations point to the fact that an increased amount of indium in the quantum dots further improves the degree of polarisation."

The micro-pyramid is constructed through crystalline growth - atom layer-by-atom layer - of the semiconductive material gallium nitride (GaN). A couple of nano-thin layers where the metal In is also included are laid on top of this, and from this the asymmetrical QDs formed at the top and light particles are emitted via a well defined wavelength.

It is claimed by the researchers that the results are open to a variety of possibilities, for example, for energy effective polarised Light Emitting Diodes (LED) in the light source for LCD screens. As the QDs can also emit one photon at a time then it is a very promising technology for quantum encryption, which is a growing technology for wire-tap proof communications. Original article available here

As with similar type of nanoscopic coating studies, the future potential of QD has been handsomely sold. However, as stated previously, DCN Corp strongly believes it can compete by providing a cost-effective and efficient nano-fabrication process. Going forward, if you and/or your colleagues are interested in making DCN Corp's alternative process reality - please ensure to contact the company as soon as practicably possible.