Abstract
Optical polarization is an indispensable component in photonic applications, the orthogonality of which extends the degree of freedom of information, and strongly polarized and highly efficient small-size emitters are essential for compact polarization-based devices. We propose a group III-nitride quantum wire for a highly-efficient, strongly-polarized emitter, the polarization anisotropy of which stems solely from its one-dimensionality. We fabricated a site-selective and size-controlled single quantum wire using the geometrical shape of a three-dimensional structure under a self-limited growth mechanism. We present a strong and robust optical polarization anisotropy at room temperature emerging from a group III-nitride single quantum wire. Based on polarization-resolved spectroscopy and strain-included 6-band k·p calculations, the strong anisotropy is mainly attributed to the anisotropic strain distribution caused by the one-dimensionality, and its robustness to temperature is associated with an asymmetric quantum confinement effect.
Highlights
Control of optical polarization is essential for photonic applications including optical image e ncryption[1], threedimensional (3D) imaging[2], and polarization-based visible light c ommunication[3]
quantum wires (QWRs) exhibit a polarization anisotropy owing to their 1D properties, including an asymmetric quantum confinement[11,12] and non-biaxial strain distribution[13]
Using III-nitride QWRs formed by a bottom-up approach, the optical polarization of the emission of the GaN QWRs formed on the m-plane[17], ultraviolet lasing with selfassembled GaN nanowires encapsulated by AlGaN18 and complex carrier dynamics with six-QWRs formed at the edge of self-assembled hexagonal GaN/AlN nanowires have been investigated[19,20]
Summary
Where P0 is the initial DLP at low temperature, A is a fitting parameter, and kBT is the thermal energy at a certain temperature. The 20 nm wide QWR shows a strong polarization anisotropy (98%) at low temperature, which is higher than that of the 50 nm wide QWR (87%). According to the experimental and calculated data, the narrow width of the QWR shows a larger effective energy level spacing than the large width. Owing to our ability to control the lateral width of the QWR using a self-limited growth mechanism, we investigated this size-dependent optical polarization anisotropy from two perspectives, namely, an asymmetric quantum confinement effect and an anisotropic strain distribution from the 1D geometry. We believe that our light-emitting platform, based on III-nitride QWRs, is a promising candidate for future photonic applications relying on the intensive use of the optical polarization, including polarizer-free display, polarization-sensitive sensing and imaging
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