Swedish Researchers Demonstrate New Method for Light Polarization

6 February 2014
 
Researchers at Linköping University in Sweden have come up with a new method that enables the generation of light with a high degree of polarization by using quantum dots. The technique could come in useful for energy-saving computer screens and wiretap-proof communications, the university says on its website.
 
In their study, published in the Nature periodical Light: Science and Applications, the researchers explain that polarized light is usually generated by using normal light that passes through a filter, which blocks the unwanted waves. However, at least 50% of the light gets lost in the process. Emitting light polarized at the source is a more successful method for polarizing light, and can be achieved with quantum dots. But these crystals of semiconductive material have so far produced polarization which is too weak or difficult to control.
 
The new innovative method, presented by the researchers, seems to successfully overcome these limitations. By using asymmetrical quantum dots of a nitride material with indium at the top of tiny six-sided pyramids, they achieved an 84% degree of linear polarization of light. The researchers used quantum dots that emit violet light with a wavelength of 415 nm, but by changing the amount of the metal indium, the photons can take on any color within the visible spectrum. Their degree of polarization can be further improved if the amount of indium in the quantum dots is increased, one of the article's authors, Fredik Karlsson, said.
 
The micropyramids used for the experiment were constructed through crystalline growth of the semiconductive material gallium nitride.