Abstract
Semiconductor quantum dots (QDs) have been demonstrated viable for efficient light emission applications, in particular for the emission of single photons on demand. However, the preparation of QDs emitting photons with predefined and deterministic polarization vectors has proven arduous. Access to linearly polarized photons is essential for various applications. In this report, a novel concept to directly generate linearly-polarized photons is presented. This concept is based on InGaN QDs grown on top of elongated GaN hexagonal pyramids, by which the predefined elongation determines the polarization vectors of the emitted photons from the QDs. This growth scheme should allow fabrication of ultracompact arrays of photon emitters, with a controlled polarization direction for each individual emitter. Researchers in Sweden have unveiled a scheme for fabricating quantum dots that emit linearly polarized light. Anders Lundskog and co-workers from Linköping University controlled the emission from InGaN quantum dots by growing them on top of miniature hexagonal GaN pyramids with elongated bases. They found that the polarization of the emitted light was aligned with the axis of elongation. In principle, the wavelength of the light emitted by the quantum dots can be tuned from ultraviolet to the infrared by adjusting the amount of indium in the InGaN. Benefits of the approach include its compatibility with high-temperature operation and large-area wafer-processing techniques. In the future, this technique could allow the realization of quantum dot-based single-photon emitters with controllable polarization on a single chip.
Highlights
Quantum dots (QDs) have validated their important role in current optoelectronic devices and they are seen promising as light sources for quantum information applications
The polarization directions of the QD emission can be guided by the orientations of the underlying elongated GaN pyramids
Such an effect can be realized as the elongated GaN pyramids provide additional in-plane confinement for the InGaN QDs implanting unidirectional in-plane anisotropy into the QDs, which subsequently emit photons linearly-polarized along the elongated direction of the GaN EHPs
Summary
Quantum dots (QDs) have validated their important role in current optoelectronic devices and they are seen promising as light sources for quantum information applications. An improved efficiency of laser diodes and light-emitting diodes can be achieved by the incorporation of QDs ensembles in the optically active layers.[1] In addition, the proposed quantum computer applications rely on photons with distinct energy and polarization vectors, which can be seen as the ultimate demand on photons emitted from individual QDs.[2] A common requirement raised for several optoelectronic applications, e.g., liquid-crystal displays, three-dimensional visualization, (bio)-dermatology[3] and the optical quantum computers,[4] is the need of linearly polarized light for their operation. The generation of linearly polarized light is obtained by passing unpolarized light through a combination of polarization selective filters and waveguides, with an inevitable efficiency loss as the result. These losses can be drastically reduced by employment of sources, which directly generate photons with desired polarization directions
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