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学者姓名:李虞锋
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Abstract :
The differences in spatially optical properties between blue and green quantum wells (QWs) in a monolithic dual-wavelength semipolar (20-21) structure were investigated by scanning near-field optical microscopy (SNOM). The shortest wavelength for green QWs and the longest wavelength for blue QWs were both discovered in the region with the largest stress. It demonstrated that In composition, compared to stress, plays a negligible role in defining the peak wavelength for blue QWs, while for green QWs, In composition strongly affects the peak wavelength. For green QWs, significant photoluminescence enhancement was observed in the defect-free region, which was not found for blue QWs. Furthermore, the efficiency droop was aggravated in the defect-free region for green QWs but reduced for blue QWs. It indicates that carrier delocalization plays a more important role in the efficiency droop for QWs of good crystalline quality, which is experimentally pointed out for the first time.
Keyword :
localization states scanning near-field optical microscopy semipolar LEDs
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GB/T 7714 | Li, Aixing , Li, Yufeng , Song, Jie et al. The Differences in Spatial Luminescence Characteristics between Blue and Green Quantum Wells in Monolithic Semipolar (20-21) LEDs Using SNOM [J]. | NANOMATERIALS , 2022 , 12 (19) . |
MLA | Li, Aixing et al. "The Differences in Spatial Luminescence Characteristics between Blue and Green Quantum Wells in Monolithic Semipolar (20-21) LEDs Using SNOM" . | NANOMATERIALS 12 . 19 (2022) . |
APA | Li, Aixing , Li, Yufeng , Song, Jie , Yang, Haifeng , Zhang, Ye , Hu, Peng et al. The Differences in Spatial Luminescence Characteristics between Blue and Green Quantum Wells in Monolithic Semipolar (20-21) LEDs Using SNOM . | NANOMATERIALS , 2022 , 12 (19) . |
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Abstract :
As a common clinical problem, the therapy of SSTIs is facing growing challenges due to an increase in the number of drug-resistant bacteria and fungi. UV C (UVC) light sterilization has been widely used in all aspects of daily life, but there are very few reports about in vivo therapy using UVC light. Due to the changes in pathogenic species and the absence of research on topical skin antibiotics, the therapy of skin and soft tissue infections (SSTIs) is facing more and more severe challenges. It is particularly urgent to look for alternative therapies without induction of drug resistance. UV C (UVC) light within the range of 200 to 280 nm is one of the most common techniques used to kill and/or inactivate pathogenic microorganisms. However, the traditional most commonly used wavelength of 254 nm irradiated from a low-pressure mercury lamp is hazardous to human health, being both carcinogenic and damaging to eye tissues, which limits its applications in vivo. This research aimed to investigate the antimicrobial properties and influence of 275-nm UVC light from a light-emitting diode (UVC-LED light) on wound healing time. Five bacteria, three fungi, and scalded-mouse models combined with SSTIs were used to evaluate the antimicrobial effect in vitro and in vivo. 275-nm UVC-LED light inactivated both bacteria and fungi with a very short irradiation time in vitro and induced neither DNA damage nor epidermal lesions in the mice's skin. Furthermore, in mouse models of SSTIs induced by either methicillin-resistant Staphylococcus aureus (MRSA) or Candida albicans, the 275-nm UVC-LED light showed significant antimicrobial effects and shortened the wound healing time compared with that in the no-irradiation group. UVC-LED light at 275 nm has the potential to be a new form of physical therapy for SSTIs.IMPORTANCE As a common clinical problem, the therapy of SSTIs is facing growing challenges due to an increase in the number of drug-resistant bacteria and fungi. UV C (UVC) light sterilization has been widely used in all aspects of daily life, but there are very few reports about in vivo therapy using UVC light. It is well known that prolonged exposure to UVC light increases the possibility of skin cancer. In addition, it is also very harmful for eyes. UV irradiation with 254-nm UVC light can cause corneal damage, like thinning of the corneal epithelial layer, superficial punctate keratitis, corneal erosion, etc. In this study, we focused on looking for a more accessible light source and safer UVC wavelength, and 275-nm UVC LED light was chosen. We investigated its applicability for SSTIs therapy with relative skin safety and expected that it could be used as a new physical therapy method for SSTIs.
Keyword :
275 nm Candida albicans MRSA skin and soft tissue infections UVC-LED
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GB/T 7714 | Song, Chenghua , Wen, Ruichao , Zhou, Jiaxuan et al. UV C Light from a Light-Emitting Diode at 275 Nanometers Shortens Wound Healing Time in Bacterium- and Fungus-Infected Skin in Mice [J]. | MICROBIOLOGY SPECTRUM , 2022 . |
MLA | Song, Chenghua et al. "UV C Light from a Light-Emitting Diode at 275 Nanometers Shortens Wound Healing Time in Bacterium- and Fungus-Infected Skin in Mice" . | MICROBIOLOGY SPECTRUM (2022) . |
APA | Song, Chenghua , Wen, Ruichao , Zhou, Jiaxuan , Zeng, Xiaoyan , Kou, Zi , Li, Yufeng et al. UV C Light from a Light-Emitting Diode at 275 Nanometers Shortens Wound Healing Time in Bacterium- and Fungus-Infected Skin in Mice . | MICROBIOLOGY SPECTRUM , 2022 . |
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Abstract :
We investigated the excitation-dependent spatially resolved luminescence properties of InGaN/GaN light-emitting diodes (LEDs) with air-cavity arrays using scanning near-field optical microscopy (SNOM), and quantified the effect of the air-cavity structure on the spatial distributions of light-extraction efficiency, internal quantum efficiency, and external quantum efficiency through experiments and numerical simulations. We found that higher light-extraction efficiency and less stress were always observed in the air-cavity areas. Compared to flat areas, the average light-extraction efficiency of the air-cavity areas was improved by 65%, and the residual stress of the air-cavity center was reduced by 89 MPa, which resulted in increased PL intensity, reduced wavelength shift, and narrowed full width at half maximum. The highest external quantum efficiency and aggravated efficiency droop were found in the air-cavity center. At 3.1 W/cm2, the external quantum efficiency and internal quantum efficiency of the air-cavity center were enhanced by 255% and 223%, respectively.
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GB/T 7714 | Li, Aixing , Li, Yufeng , Yang, Haifeng et al. Excitation-dependent spatially resolved photoluminescence in InGaN/GaN LEDs with air-cavity arrays grown on patterned sapphire substrates [J]. | OPTICAL MATERIALS EXPRESS , 2022 , 12 (12) : 4518-4527 . |
MLA | Li, Aixing et al. "Excitation-dependent spatially resolved photoluminescence in InGaN/GaN LEDs with air-cavity arrays grown on patterned sapphire substrates" . | OPTICAL MATERIALS EXPRESS 12 . 12 (2022) : 4518-4527 . |
APA | Li, Aixing , Li, Yufeng , Yang, Haifeng , Zhang, Minyan , Tian, Zhenhuan , Li, Qiang et al. Excitation-dependent spatially resolved photoluminescence in InGaN/GaN LEDs with air-cavity arrays grown on patterned sapphire substrates . | OPTICAL MATERIALS EXPRESS , 2022 , 12 (12) , 4518-4527 . |
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Abstract :
The selective area growth (SAG) technique enables the creation of multi-color micro-structures. However, the substrate pattern to obtain multi-color and mass transfer of these micro-structures are complicated to achieve. Moreover, high dislocation density as well as large residual stress in c-plane quantum wells still remain challenges. Here, an improved SAG strategy was proposed to achieve completely merged asymmetric pyramids on closely connected deep-concave holes via the lateral overgrowth of adjacent pyramids. These asymmetric pyramids were directly grown on the sapphire substrate, making mass transfer be possible. Growth rate distinction appears at the different positions of the overgrowth region, resulting in a multi-wavelength emission. More importantly, the residual stress and the dislocation density can be suppressed by utilizing the deep-hole pattern and lateral overgrowth, contributing to a lower piezoelectric polarization field and a higher spontaneous emission rate. These ultrafast and high-efficient multi-color micro-LEDs are suitable for the application in highresolution display, flexible devices, and high-speed visible-light-communication.
Keyword :
Deep-hole pattern Lateral overgrowth Microstructures Stress and defect
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GB/T 7714 | Tian, Zhenhuan , Zhang, Weihan , Wang, Xuzheng et al. Completely merged multi-color asymmetric pyramid with suppressed stress and defect density [J]. | JOURNAL OF CRYSTAL GROWTH , 2021 , 570 . |
MLA | Tian, Zhenhuan et al. "Completely merged multi-color asymmetric pyramid with suppressed stress and defect density" . | JOURNAL OF CRYSTAL GROWTH 570 (2021) . |
APA | Tian, Zhenhuan , Zhang, Weihan , Wang, Xuzheng , Li, Qiang , Su, Xilin , Li, Yufeng et al. Completely merged multi-color asymmetric pyramid with suppressed stress and defect density . | JOURNAL OF CRYSTAL GROWTH , 2021 , 570 . |
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Abstract :
We reported the second- and third-order temporal interference of two non-degenerate pseudo-thermal sources in a nitrogen-vacancy center (NV-). The relationship between the indistinguishability of source and path alternatives is analyzed at low temperature. In this article, we demonstrate the switching between three-mode bunching and frequency beating effect controlled by the time offset and the frequency difference to realize optical demultiplexer. Our experimental results suggest the advanced technique achieves channel spacing and speed of the demultiplexer of about 96% and 17 ns, respectively. The proposed demultiplexer model will have potential applications in quantum computing and communication.
Keyword :
nitrogen vacancy center diamond optical demultiplexer quantum computing and communications
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GB/T 7714 | Li, Xinghua , Raza, Faizan , Li, Yufeng et al. Demultiplexer of Multi-Order Correlation Interference in Nitrogen Vacancy Center Diamond [J]. | MATERIALS , 2021 , 14 (22) . |
MLA | Li, Xinghua et al. "Demultiplexer of Multi-Order Correlation Interference in Nitrogen Vacancy Center Diamond" . | MATERIALS 14 . 22 (2021) . |
APA | Li, Xinghua , Raza, Faizan , Li, Yufeng , Wang, Jinnan , Wang, Jinhao , Ali, Hasnain et al. Demultiplexer of Multi-Order Correlation Interference in Nitrogen Vacancy Center Diamond . | MATERIALS , 2021 , 14 (22) . |
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Abstract :
Modulation bandwidth and the emission region are essential features for the widespread use of visible light communications (VLC). This paper addresses the contradictory requirements to achieve broadband and proposes ultrafast, asymmetric pyramids grown on adjacent deep concave holes via lateral overgrowth. Multicolor emission with an emission region between 420 nm and 600 nm is obtained by controlling the growth rate at different positions on the same face, which also can provide multiple subcarrier frequency points for the employment of wavelength division multiplexing technology. The spontaneous emission rate distinction is narrowed by lowering the number of the crystal plane, ensuring a high modulation bandwidth over broadband. More importantly, the residual stress and dislocation density were minimized by employing a patterned substrate, and lateral overgrowth resulted in a further enhancement of the recombination rate. Finally, the total modulation bandwidth of multiple subcarriers of the asymmetric pyramids is beyond GHz. These ultrafast, multicolor microLEDs are viable for application in VLC systems and may also enable applications for intelligent lighting and display. (C) 2021 Chinese Laser Press
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GB/T 7714 | Tian, Zhenhuan , Li, Qiang , Wang, Xuzheng et al. Phosphor-free microLEDs with ultrafast and broadband features for visible light communications [J]. | PHOTONICS RESEARCH , 2021 , 9 (4) : 452-459 . |
MLA | Tian, Zhenhuan et al. "Phosphor-free microLEDs with ultrafast and broadband features for visible light communications" . | PHOTONICS RESEARCH 9 . 4 (2021) : 452-459 . |
APA | Tian, Zhenhuan , Li, Qiang , Wang, Xuzheng , Zhang, Mingyin , Su, Xilin , Zhang, Ye et al. Phosphor-free microLEDs with ultrafast and broadband features for visible light communications . | PHOTONICS RESEARCH , 2021 , 9 (4) , 452-459 . |
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Abstract :
Multimode and random directionalities are major issues restricting the application of whispering gallery mode microcavity lasers. We demonstrated a 40 mu m diameter microring with an off-centered embedded hole and warped geometry from strained III-nitride quantum well multilayers. Single-mode directional whispering gallery mode lasing was achieved by the warped structure and high-order mode suppression induced by the off-centered hole. In addition, the introduction of the off-centered hole reduced the lasing threshold from 3.24 to 2.79 MW/cm(2) compared with the warped microdisk without an embedded hole while maintaining a high-quality factor of more than 4000. Directional light emission in 3D was achieved and attributed to the warped structure, which provides a vertical component of the light emission, making it promising for building multifunctional coherent light sources in optoelectronic integration. (C) 2021 Chinese Laser Press
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GB/T 7714 | Zhang, Shengnan , Li, Yufeng , Hu, Peng et al. Realization of directional single-mode lasing by a GaN-based warped microring [J]. | PHOTONICS RESEARCH , 2021 , 9 (4) : 432-438 . |
MLA | Zhang, Shengnan et al. "Realization of directional single-mode lasing by a GaN-based warped microring" . | PHOTONICS RESEARCH 9 . 4 (2021) : 432-438 . |
APA | Zhang, Shengnan , Li, Yufeng , Hu, Peng , Tian, Zhenhuan , Li, Qiang , Li, Aixing et al. Realization of directional single-mode lasing by a GaN-based warped microring . | PHOTONICS RESEARCH , 2021 , 9 (4) , 432-438 . |
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Abstract :
The hexagonal boron nitride (hBN) and BAlN films were prepared by RF-sputtering, which were used as the low and high refractive index layers. A series of hBN/BAlN distributed Bragg reflectors (DBRs)were prepared on sapphire substrate. The reflectivity of 9-pair hBN/BAlN (39 nm/33 nm) DBR reached 90% at 300 nm with a bandwidth of 45 nm, and which of 6-pair hBN/BAlN (35 nm/29 nm) reached 52% at 280 nm. The hBN/BAlN DBRs can be used to achieve higher reflectivity in shorter UV bands with the improvement of BAlN material quality through the growth condition optimization. Funding. Fundamental Research Funds for the Central Universities (XJJ2017011); National Key Research and Development Program of China (2016YFB0400801). © 2020 © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Keyword :
Boron nitride Distributed Bragg reflectors III-V semiconductors Nitrides Reflection Refractive index Sapphire
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GB/T 7714 | LI, QIANG , ZHANG, QIFAN , BAI, YUNHE et al. Deep-UV hexagonal boron nitride (hBN)/BAlN distributed Bragg reflectors fabricated by RF-sputtering [J]. | Optical Materials Express , 2021 , 11 (1) : 180-188 . |
MLA | LI, QIANG et al. "Deep-UV hexagonal boron nitride (hBN)/BAlN distributed Bragg reflectors fabricated by RF-sputtering" . | Optical Materials Express 11 . 1 (2021) : 180-188 . |
APA | LI, QIANG , ZHANG, QIFAN , BAI, YUNHE , ZHANG, HAORAN , HU, P.E.N.G , LI, YUFENG et al. Deep-UV hexagonal boron nitride (hBN)/BAlN distributed Bragg reflectors fabricated by RF-sputtering . | Optical Materials Express , 2021 , 11 (1) , 180-188 . |
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Abstract :
We have fabricated a tubular whispering gallery mode laser based on InGaN/GaN quantum wells and transferred it onto a flexible substrate. Compared with those without the transferring processes, the threshold energy density was reduced by 60%, at about 25.55 mu J/cm(2), while a high-quality factor of > 15,000 was obtained. Finite-difference time-domain simulation demonstrated that such a low threshold energy density can be attributed to the decreased mode volume, from 1.32 x 10(-3) mu m(3) to 6.92 x 10(-4) mu m(3). The wavelength dependences on strain were found to be 5.83 nm, 1.38 nm, and 2.39 nm per stretching unit epsilon in the X, Y, and Z directions, respectively. Such strain sensitivity was attributed to the deformation of the GaN microtube and the change in the refractive index of the PDMS.
Keyword :
cavity microtube WGM
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GB/T 7714 | Hu, Peng , Li, Yufeng , Zhang, Shengnan et al. Low-Threshold and Wavelength-Tunable InGaN Tubular WGM Laser Embedded in a Flexible Substrate [J]. | CRYSTALS , 2021 , 11 (10) . |
MLA | Hu, Peng et al. "Low-Threshold and Wavelength-Tunable InGaN Tubular WGM Laser Embedded in a Flexible Substrate" . | CRYSTALS 11 . 10 (2021) . |
APA | Hu, Peng , Li, Yufeng , Zhang, Shengnan , Zhang, Ye , Tian, Zhenhuan , Yun, Feng . Low-Threshold and Wavelength-Tunable InGaN Tubular WGM Laser Embedded in a Flexible Substrate . | CRYSTALS , 2021 , 11 (10) . |
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Abstract :
BAlN is a promising ultrawide bandgap semiconductor, but systematic studies of its bandgap are scarce. Here, bandgap engineering of BAlN containing the phase transition factor (from hexagonal to wurtzite structures) has been investigated by DFT calculations and verified experimentally. The calculated bandgap bowing parameter of hexagonal BAlN (h-BAlN) is 2.29 eV, while the bandgap bowing parameters of wurtzite BAlN (w-BAlN) are −4.09 eV and 2.48 eV in the B-rich and Al-rich regions, respectively. Meanwhile, calculations indicate that BAlN preferentially forms w-BAlN at Al composition above 18.7%. So, the bandgap variation of BAlN is divided into three regions based on Al composition: h-BAlN (0–18.7%), B-rich w-BAlN (18.7%–50%), Al-rich w-BAlN (50%–1), and each has its own trend. Experimentally, h-BAlN and w-BAlN films were prepared by magnetron co-sputtering technique and the phase transition was observed in X-ray diffraction (XRD) patterns. h-BAlN shows a typical triangular morphology and the Raman and XRD peaks are located at 1371 cm−1 and 44.3°, tending to (1 0 1) h-BN. w-BAlN has a 'needle-felt' surface with Raman and XRD peaks at 656 cm−1 and 35.9°, tending to (0 0 2) w-AlN. The experimental bandgap variation of BAlN shows a 'W' shape, which can be well explained by the calculation results. © 2021
Keyword :
Aluminum Aluminum nitride Boron nitride Density functional theory Energy gap III-V semiconductors Morphology Nitrides X ray diffraction Zinc sulfide
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GB/T 7714 | Zhang, Qifan , Li, Qiang , Zhang, Weihan et al. Phase transition and bandgap engineering in B1-xAlxN alloys: DFT calculations and experiments [J]. | Applied Surface Science , 2021 , 575 . |
MLA | Zhang, Qifan et al. "Phase transition and bandgap engineering in B1-xAlxN alloys: DFT calculations and experiments" . | Applied Surface Science 575 (2021) . |
APA | Zhang, Qifan , Li, Qiang , Zhang, Weihan , Zhang, Haoran , Zheng, Feng , Zhang, Mingyin et al. Phase transition and bandgap engineering in B1-xAlxN alloys: DFT calculations and experiments . | Applied Surface Science , 2021 , 575 . |
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