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A semiconductive materials research group led by Per Olof Holtz, a professor at Linköping University, have now developed an alternative method.
The concept is based on InGaN QDs grown on top of elongated GaN hexagonal pyramids, by which the predefined elongation determines the polarisation vectors of the emitted photons from the QDs. This growth scheme should allow fabrication of ultra-compact arrays of photon emitters, with a controlled polarisation direction for each individual emitter.
With these, they have succeeded in creating light with a high degree of linear polarisation, on average 84 percent. The results are being published in the Nature periodical Light: Science & Applications.
“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,” Holtz says.
In experiments, quantum dots were used that emit violet light with a wavelength of 415 nm, but the photons can in principle take on any colour at all within the visible spectrum by varying the indium content.
improves the degree of polarisation,” says reader Fredrik Karlsson, one of the authors of the article.
The micropyramid is constructed through crystalline growth, atom layer by atom layer, of the semiconductive material GaN. A couple of nanothin layers where the metal indium is also included are laid on top of this. From the asymmetrical quantum dot thus formed at the top, light particles are emitted with a well-defined wavelength.
The results of the research are opening up possibilities, for example for more energy-effective polarised LEDs in the light source for LCD screens. As the quantum dots can also emit one photon at a time, this is very promising technology for quantum encryption, a growing technology for wiretap-proof communications.
The work is described in detail in the article, “Direct generation of linearly polarised photon emission with designated orientations from site-controlled InGaN quantum dots,” by A. Lundskog et al inScience & Applications (2014) 3, e139, published online on 31st January 2014. doi:10.1038/lsa.2014.20
The project has been conducted within Nano-N consortium funded by the Swedish Foundation for Strategic Research.
Vishay launches 850 nm IR GaAs based IR emitter
The gallium arsenide device features radiant intensity to 350 mW/sr at 1 A, optical power to 660 mW, and thermal resistivity down to 10 K/W
Vishay Intertechnology has broadened its optoelectronics portfolio with the release of a new 850 nm infrared (IR) emitter in a compact 3.85 mm by 3.85 mm by 2.24 mm top-view SMD package.
Two ways of creating polarised light (Credit: Fredrik Karlsson, LiU)
“Our theoretical calculations point to the fact that an increased amount of indium in the quantum dots further
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www.compoundsemiconductor.net March 2014
Based on SurfLight surface emitter chip technology and featuring an integrated lens, the VSMY98545 offers high drive current capability, high radiant intensity, and high optical power while providing low thermal resistivity.
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