A full structure 290 nm ultraviolet light emitting diode(UV-LED)with a nanoporous n-AlGaN underlayer was fabricated by top via hole formation followed by high-voltage electrochemical etching.The 20 to 120 nm nanopores...A full structure 290 nm ultraviolet light emitting diode(UV-LED)with a nanoporous n-AlGaN underlayer was fabricated by top via hole formation followed by high-voltage electrochemical etching.The 20 to 120 nm nanopores were prepared in regular doped n-AlGaN by adjusting the etching voltage.The comparison between the Raman spectrum and the photoluminescence wavelength shows that the biaxial stress in the nanoporous material is obviously relaxed.The photoluminescence enhancement was found to be highly dependent on the size of the pores.It not only improves the extraction efficiency of top-emitting transverse-electric(TE)-mode photons but also greatly improves the efficiency of side emitting tran sverse-magnetic(TM)-mode photons.This leads to the polarization change of the side-emitting light from-0.08 to-0.242.The intensity of the electroluminescence was increased by 36.5%at 100 mA,and the efficiency droop at high current was found to decrease from 61%to 31%.展开更多
With the development of high harmonic generation(HHG),lensless extreme-ultraviolet(XUV)imaging at nanoscale resolution has become possible with table-top systems.Specifically,ptychographic phase retrieval using monoch...With the development of high harmonic generation(HHG),lensless extreme-ultraviolet(XUV)imaging at nanoscale resolution has become possible with table-top systems.Specifically,ptychographic phase retrieval using monochromatic XUV illumination exhibits extraordinary robustness and accuracy to computationally reconstruct the object and the illumination beam profile.In ptychography,using structured illumination has been shown to improve reconstruction robustness and image resolution by enhancing high spatial-frequency diffraction.However,broadband imaging has remained challenging,as the required multiwavelength algorithms become increasingly demanding.One major aspect is the ability to separate the available information into different physically meaningful states,such as different spectral components.Here,we show that introducing spatial diversity between spectral components of an HHG beam can significantly improve the reconstruction quality in multiwavelength XUV ptychography.We quantify the diversity in the polychromatic illumination by analyzing the diffraction patterns using established geometry-and information-theory-based dissimilarity metrics.We experimentally verify the major influence of diversity by comparing ptychography measurements using HHG beams with Gaussian and binary structured profiles as well as with beams carrying wavelength-dependent orbital angular momentum.Our results demonstrate how structured illumination acts in twofold by separating the spectral information in a single diffraction pattern while providing maximized added information with every new scan position.We anticipate our work to be a starting point for high-fidelity polychromatic imaging of next-generation nanostructured devices at XUV and soft-X-ray wavelengths.展开更多
基金National Natural Science Foundation of China(61574114,61774121)National Key Research and Development Program of China(2016YFB0400801)Fundamental Research Funds for the Central Universities(Z201805198).
文摘A full structure 290 nm ultraviolet light emitting diode(UV-LED)with a nanoporous n-AlGaN underlayer was fabricated by top via hole formation followed by high-voltage electrochemical etching.The 20 to 120 nm nanopores were prepared in regular doped n-AlGaN by adjusting the etching voltage.The comparison between the Raman spectrum and the photoluminescence wavelength shows that the biaxial stress in the nanoporous material is obviously relaxed.The photoluminescence enhancement was found to be highly dependent on the size of the pores.It not only improves the extraction efficiency of top-emitting transverse-electric(TE)-mode photons but also greatly improves the efficiency of side emitting tran sverse-magnetic(TM)-mode photons.This leads to the polarization change of the side-emitting light from-0.08 to-0.242.The intensity of the electroluminescence was increased by 36.5%at 100 mA,and the efficiency droop at high current was found to decrease from 61%to 31%.
基金Toegepaste en Technische Wetenschappen,NWO(P16-08)European Research Council(ERC)(864016).
文摘With the development of high harmonic generation(HHG),lensless extreme-ultraviolet(XUV)imaging at nanoscale resolution has become possible with table-top systems.Specifically,ptychographic phase retrieval using monochromatic XUV illumination exhibits extraordinary robustness and accuracy to computationally reconstruct the object and the illumination beam profile.In ptychography,using structured illumination has been shown to improve reconstruction robustness and image resolution by enhancing high spatial-frequency diffraction.However,broadband imaging has remained challenging,as the required multiwavelength algorithms become increasingly demanding.One major aspect is the ability to separate the available information into different physically meaningful states,such as different spectral components.Here,we show that introducing spatial diversity between spectral components of an HHG beam can significantly improve the reconstruction quality in multiwavelength XUV ptychography.We quantify the diversity in the polychromatic illumination by analyzing the diffraction patterns using established geometry-and information-theory-based dissimilarity metrics.We experimentally verify the major influence of diversity by comparing ptychography measurements using HHG beams with Gaussian and binary structured profiles as well as with beams carrying wavelength-dependent orbital angular momentum.Our results demonstrate how structured illumination acts in twofold by separating the spectral information in a single diffraction pattern while providing maximized added information with every new scan position.We anticipate our work to be a starting point for high-fidelity polychromatic imaging of next-generation nanostructured devices at XUV and soft-X-ray wavelengths.
