Fabrication and Optical Properties of Three-Dimensional Zinc Oxide Photonic Crystals

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Over the past two decades photonic crystals (PhCs) have emerged as a promising new class of materials which offers unprecedented control of light in materials. Recently, atomic layer deposition (ALD) has been shown to be a powerful tool for the infiltration of 3D templates with dielectric or semiconducting materials, which has opened new possibilities for PhC fabrication. Here we report on the development and optical characterization of optically active ZnO PhCs for the ultraviolet (UV) to visible spectrum. We have fabricated ZnO inverse opal structures by infiltrating polystyrene opal templates using a low-temperature ALD process. The resulting structures have high filling fractions, possess photonic band gaps in the near-UV to visible spectrum, and exhibit efficient photoluminescence. We demonstrate room temperature UV lasing in the ZnO photonic crystals, which can simultaneously confine light and provide optical gain. For small lattice constants, we observe random lasing due to disorder in the structures when the photonic pseudogaps are located away from the ZnO gain spectrum. Tuning the primary photonic band gap to the ZnO gain peak leads to a five-fold reduction in lasing threshold due to the enhanced confinement of light. In contrast, highly directional photonic crystal lasing with tunable wavelength is achieved in bands with abnormally low group velocity in the high-order band structure. This demonstrates that the high-order band structure of three-dimensional photonic crystals can be used to effectively confine light and enhance emission. Finally we have measured angle- and polarization-resolved reflection and emission properties of ZnO inverse opals. The reflection spectra are explained in terms of multiple Bragg diffraction and the resulting coupling of modes, and the polarization-dependence of reflection features is discussed. We also observe strongly modified spontaneous emission from the PhCs, with suppression due to the primary PBG and strong angular and spectral redistribution of emission in the higher-order band structure. This suggest that in high-quality 3D PhCs significant changes in the radiation pattern can be achieved, which offers possible applications for the tailoring of highly efficient light sources.

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  • 07/30/2018
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