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1.
Front Neurol ; 15: 1365876, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38895698

RESUMEN

Objective: Whether the efficacy of combined stent retriever and contact aspiration (S + A) is superior to stent retriever (S) alone for revascularisation in patients with large vessel occlusive stroke remains uncertain. The aim of this meta-analysis was to assess the safety and efficacy of combined stent retriever and contact aspiration for the treatment of acute ischaemic stroke with large vessel occlusion by comparing it with stent retriever alone. Methods: We systematically searched the PubMed, Embase, Web of Science, and The Cochrane Library databases for randomised controlled trials and observational studies (case-control and cohort studies) published before 1 October 2023 comparing the efficacy of combined stent retriever and contact aspiration versus tent retriever alone in patients with large vessel occlusive stroke. The end point of the primary efficacy observed in this meta-analysis study was the rate of first pass nearly complete or complete recanalisation (mTICI 2c-3). Secondary effectiveness nodes were: rate of first pass successful recanalisation (mTICI 2b-3), rate of near-complete or complete recanalisation of the postoperative vessel, rate of successful recanalisation of the postoperative vessel, and MRS 0-2 within 90 days. Safety endpoints were interoperative embolism, symptomatic intracranial haemorrhage, and mortality within 90 days. Results: A total of 16 studies were included in the literature for this meta-analysis, with a total of 7,320 patients (S + C group: 3,406, S group: 3,914). A comprehensive analysis of the included literature showed that combined stent retriever and contact aspiration had a higher rate of near-complete or complete recanalisation of the postoperative vessel [OR = 1.53, 95% CI (1.24, 1.88), p < 0.0001] and rate of successful recanalisation of the postoperative vessel compared to stent retriever alone [OR = 1.83, 95% CI (1.55, 2.17), p < 0.00001]; there were no statistically significant differences between the two groups in terms of the rate of first pass nearly complete or complete recanalisation [OR = 1.00, 95% CI (0.83, 1.19), p = 0.96], rate of first pass successful recanalisation [OR = 1.02, 95% CI (0.85, 1.24), p = 0.81], interoperative embolism [OR = 0.93, 95% CI (0.72, 1.20), p = 0.56], symptomatic intracranial haemorrhage [OR = 1.14, 95% CI (0.87, 1.48), p = 0.33], MRS 0-2 within 90 days [OR = 0.89, 95% CI (0.76, 1.04), p = 0.14] and mortality within 90 days [OR = 1.11, 95% CI (0.94, 1.31), p = 0.22]. Conclusion: Combined stent retriever and contact aspiration has a higher rate of postprocedural revascularisation (mTICI 2c-3/mTICI 2b-3) compared with stent retriever alone in patients with large vessel occlusion stroke. In addition, it was not superior to stenting alone in terms of the rate of first pass recanalisation (mTICI 2c-3/mTICI 2b-3), interoperative embolisation, symptomatic intracranial haemorrhage, good functional prognosis within 90 days and mortality within 90 days.

2.
Front Neurol ; 15: 1301277, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38523616

RESUMEN

Background: Traumatic brain injury (TBI) is a brain function injury caused by external mechanical injury. Primary and secondary injuries cause neurological deficits that mature brain tissue cannot repair itself. Stem cells can self-renewal and differentiate, the research of stem cells in the pathogenesis and treatment of TBI has made significant progress in recent years. However, numerous articles must be summarized to analyze hot spots and predict trends. This study aims to provide a panorama of knowledge and research hotspots through bibliometrics. Method: We searched in the Web of Science Core Collection (WoSCC) database to identify articles pertaining to TBI and stem cells published between 2000 and 2022. Visualization knowledge maps, including co-authorship, co-citation, and co-occurrence analysis were generated by VOSviewer, CiteSpace, and the R package "bibliometrix." Results: We retrieved a total of 459 articles from 45 countries. The United States and China contributed the majority of publications. The number of publications related to TBI and stem cells is increasing yearly. Tianjin Medical University was the most prolific institution, and Professor Charles S. Cox, Jr. from the University of Texas Health Science Center at Houston was the most influential author. The Journal of Neurotrauma has published the most research articles on TBI and stem cells. Based on the burst references, "immunomodulation," "TBI," and "cellular therapy" have been regarded as research hotspots in the field. The keywords co-occurrence analysis revealed that "exosomes," "neuroinflammation," and "microglia" were essential research directions in the future. Conclusion: Research on TBI and stem cells has shown a rapid growth trend in recent years. Existing studies mainly focus on the activation mechanism of endogenous neural stem cells and how to make exogenous stem cell therapy more effective. The combination with bioengineering technology is the trend in this field. Topics related to exosomes and immune regulation may be the future focus of TBI and stem cell research.

3.
J Appl Psychol ; 108(6): 889-904, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-36227307

RESUMEN

Growing diversity in the workforce has compelled scholars and managers to create inclusive organizational environments for employees who belong to marginalized groups. Yet, little is known about how employees with stigmatized medical conditions manage their job demands. In this article, we examine the role of stigma associated with human immunodeficiency virus (HIV) in shaping the ability of employees with HIV to contribute to their organizations. Drawing on stigma and emotions literatures, we investigate the influence of HIV stigma on job effectiveness (i.e., in-role performance and organizational citizenship behaviors) through the mediated paths of fear and shame. We further examine whether a psychological (i.e., core self-evaluation [CSE]) and a physiological (i.e., CD4 cell count, defined as the biological indicator of HIV severity) factor would moderate these mediating relationships at the first and second stages, respectively. Using a sample of 225 employees with HIV surveyed across three measurement periods with a time lag of 3 months, we found support for the dual-stage moderated mediation model linking HIV stigma and job effectiveness via shame under lower (vs. higher) levels of CSE and CD4 cell count. By contrast, we did not find evidence for the mediating role of fear. Implications of our findings for theory and practice are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).


Asunto(s)
Infecciones por VIH , Estigma Social , Humanos , Emociones , Vergüenza , Miedo
4.
J Opt Soc Am A Opt Image Sci Vis ; 39(8): 1498-1504, 2022 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-36215595

RESUMEN

This research explores the focusing characteristics of a polarization mixing quadratic space-variant phase-modulated sinh-Gaussian vortex beam. Various intriguing evolutionary trends of the focal pattern are demonstrated by the modulation of each parameter. The results show that the adjustable parameter C makes the focusing spot form an optical chain structure. The length of the structure and the number of dark optical traps in the structure can be altered by adjusting C. Simultaneously, the variation of beam order m will cause focal spot deformation. Moreover, the variation of the focal pattern indicates that polarization parameter B has the ability to adjust the position of the spot. In addition, the influence of topological charge l on the component field is also discussed. With the introduction of a polarization mixing quadratic space-variant phase, the focal pattern obtains a series of unique characteristics. These results have potential value for cutting-edge optical applications such as optical shaping, optical transmission, and multiple optical capture.

5.
Nano Lett ; 22(14): 5681-5688, 2022 Jul 27.
Artículo en Inglés | MEDLINE | ID: mdl-35819950

RESUMEN

Overcoming the challenges of patterning luminescent materials will unlock additive and more sustainable paths for the manufacturing of next-generation on-chip photonic devices. Electrohydrodynamic (EHD) inkjet printing is a promising method for deterministically placing emitters on these photonic devices. However, the use of this technique to pattern luminescent lead halide perovskite nanocrystals (NCs), notable for their defect tolerance and impressive optical and spin coherence properties, for integration with optoelectronic devices remains unexplored. In this work, we additively deposit nanoscale CsPbBr3 NC features on photonic structures via EHD inkjet printing. We perform transmission electron microscopy of EHD inkjet printed NCs to demonstrate that the NCs' structural integrity is maintained throughout the printing process. Finally, NCs are deposited with sub-micrometer control on an array of parallel silicon nitride nanophotonic cavities and demonstrate cavity-emitter coupling via photoluminescence spectroscopy. These results demonstrate EHD inkjet printing as a scalable, precise method to pattern luminescent nanomaterials for photonic applications.

6.
ACS Appl Mater Interfaces ; 14(21): 24856-24863, 2022 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-35476925

RESUMEN

Extending the operation wavelength of silicon photonics to the mid-infrared (mid-IR) band will significantly benefit critical application areas, including health care, astronomy, and chemical sensing. However, a major hurdle for mid-IR silicon photonics has been the lack of high-speed, high-responsivity, and low noise-equivalent power (NEP) photodetectors. Here, we demonstrate a van der Waals (vdW) heterostructure mid-IR photodetector integrated on a silicon-on-insulator (SOI) waveguide. The detector is composed of vertically stacked black phosphorus (BP)/molybdenum ditelluride (MoTe2). We measured high responsivity (up to 0.85 A/W) over a 3-4 µm spectral range, indicating that waveguide-confined light could strongly interact with vdW heterostructures on top. In addition, the waveguide-integrated detector could be modulated at high speed (>10 MHz) and its switching performance shows excellent stability. These results, together with the noise analysis, indicate that the NEP of the detector is as low as 8.2 pW/Hz1/2. This reported critical missing piece in the silicon photonic toolbox will enable the wide-spread adoption of mid-IR integrated photonic circuits.

7.
Appl Opt ; 60(21): 6128-6134, 2021 Jul 20.
Artículo en Inglés | MEDLINE | ID: mdl-34613276

RESUMEN

Based on the vector diffraction theory, this paper investigates the focusing properties of linearly polarized Lorentz-Gaussian vortex beams with sinusoidal phase modulation and discusses the focused light intensity under different parameters in detail. Results show that the focus pattern in the horizontal direction at the focal region can be compressed by increasing the relative Gaussian parameter wx. As the relative Lorentz parameter γy increases, the focus pattern will separate in the vertical direction of the optical field. With the topological charge number m increases, a special tunable optical dark trap focusing mode can be obtained. Through changing the sinusoidal modulation parameter n, the regular trilateral, quadrangle, pentagon, and hexagon shapes of the focusing mode can be correspondingly constructed. Besides, on increasing propagation distance z, the focusing mode in the near focusing region gradually extends outside and always exhibits hexagon-shaped patterns, which reflects that this special focusing mode has a good stability. In addition, the optical gradient force distributions and the field intensity distributions in the longitudinal plane are also investigated to illuminate the applications of these alterable focal patterns. Those novel, to the best of our knowledge, findings may be helpful in applications such as optical manipulation, optical focusing, and imaging.

8.
Appl Opt ; 60(12): 3327-3337, 2021 Apr 20.
Artículo en Inglés | MEDLINE | ID: mdl-33983236

RESUMEN

Based on the vector diffraction theory, this paper focuses on the focusing pattern of cosh-Gaussian beams with polarization mixing cosine phase modulation and discusses the focused optical intensity under different parameters in detail. The results that show by adjusting the polarization parameter C, a tunable focal shift and a continuous shifting of focus on both directions of the optical axis can be achieved and the component that dominates the intensity distribution of the total field can be changed. When the tunable parameter D is positive, the optical chain with tunable length can be structured by increasing D. When D is negative, there will appear one special optical trap focus mode by which the number of optical traps can be changed by tailoring D. When the phase modulation parameter m increases, the focal pattern will wholly enlarge and stretch along the radial direction, changing from two intensity peaks to six optical chains. By increasing the decentered parameter ß, the shape of the light intensity distribution in the focusing region can be remarkably adjusted. Besides, by combining the theories and analyzing the field patterns in the transverse plane, there is an electric field intensity dependence on the azimuthal angle φ. Those novel findings may be helpful in the applications such as optical manipulation, optical focusing, and imaging.

9.
Appl Opt ; 60(4): 929-934, 2021 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-33690400

RESUMEN

Based on the vector diffraction theory, this paper investigates the focusing and propagation characteristics of a Bessel-Gaussian beam with a power-order mixing helical-conical wavefront. It discusses the focused light intensity, optical gradient force distribution, and propagation characteristics under different parameters in detail. The results show that the topological charge number L can finely adjust the opening of the spiral-like curve at the focal plane. The power order n can adjust the energy distribution in the focus area. By increasing the eccentricity parameters K, the position of the maximum intensity spot will move along with the y coordinate axis. When the beam parameter ß increases, the number of intensity peaks on the focal plane increases. As the propagation distance z increases, the pattern of intensity distribution will change from an ellipse to "doughnut-like." Then a circular dark core will appear in the center of the light, and the propagation mode will gradually become an optical trap. Some optical gradient force distributions also are investigated to illuminate the applications of these alterable focal patterns.

10.
Food Chem (Oxf) ; 3: 100059, 2021 Dec 30.
Artículo en Inglés | MEDLINE | ID: mdl-35415641

RESUMEN

4-Hydroxybenzoic acid (4HBA) and its esterified forms can be used as preservatives in the pharmaceutical and food industries. Here, we reported the establishment of a coenzyme-A (CoA) free multi-enzyme cascade in Escherichia coli to utilize biobased L-tyrosine for efficient synthesis of 4HBA. The multi-enzyme cascade contains L-amino acid deaminase from Proteus mirabilis, hydroxymandelate synthase from Amycolatopsis orientalis, (S)-mandelate dehydrogenase and benzoylformate decarboxylase from Pseudomonas putida, and aldehyde dehydrogenase from Saccharomyces cerevisiae. The whole-cell biocatalysis afforded the synthesis of 128 ± 1 mM of 4HBA (17.7 ± 0.1 g/L) from 150 mM L-tyrosine with > 85% conversion within 96 h. In addition, the artificial enzymatic cascade also allowed the synthesis of benzoic acid from 100 mM L-phenylalanine with a conversion âˆ¼ 90%. In summary, our research offers a sustainable alternative for synthesizing 4HBA and benzoic acid from renewable feedstocks.

11.
Nano Lett ; 20(9): 6824-6830, 2020 Sep 09.
Artículo en Inglés | MEDLINE | ID: mdl-32816495

RESUMEN

Light-emitting diodes (LEDs) based on III-V/II-VI materials have delivered a compelling performance in the mid-infrared (mid-IR) region, which enabled wide-ranging applications in sensing, including environmental monitoring, defense, and medical diagnostics. Continued efforts are underway to realize on-chip sensors via heterogeneous integration of mid-IR emitters on a silicon photonic chip, but the uptake of such an approach is limited by the high costs and interfacial strains, associated with the processes of heterogeneous integrations. Here, the black phosphorus (BP)-based van der Waals (vdW) heterostructures are exploited as room-temperature LEDs. The demonstrated devices emit linearly polarized light, and the spectra cover the technologically important mid-IR atmospheric window. Additionally, the BP LEDs exhibit fast modulation speed and exceptional operation stability. The measured peak extrinsic quantum efficiency is comparable to the III-V/II-VI mid-IR LEDs. By leveraging the integrability of vdW heterostructures, we further demonstrate a silicon photonic waveguide-integrated BP LED.

12.
Nano Lett ; 20(7): 5292-5300, 2020 Jul 08.
Artículo en Inglés | MEDLINE | ID: mdl-32519865

RESUMEN

Monolayer transition-metal dichalcogenides (TMDs) are the first truly two-dimensional (2D) semiconductor, providing an excellent platform to investigate light-matter interaction in the 2D limit. The inherently strong excitonic response in monolayer TMDs can be further enhanced by exploiting the temporal confinement of light in nanophotonic structures. Here, we demonstrate a 2D exciton-polariton system by strongly coupling atomically thin tungsten diselenide (WSe2) monolayer to a silicon nitride (SiN) metasurface. Via energy-momentum spectroscopy of the WSe2-metasurface system, we observed the characteristic anticrossing of the polariton dispersion both in the reflection and photoluminescence spectrum. A Rabi splitting of 18 meV was observed which matched well with our numerical simulation. Moreover, we showed that the Rabi splitting, the polariton dispersion, and the far-field emission pattern could be tailored with subwavelength-scale engineering of the optical meta-atoms. Our platform thus opens the door for the future development of novel, exotic exciton-polariton devices by advanced meta-optical engineering.

13.
J Agric Food Chem ; 68(9): 2623-2630, 2020 Mar 04.
Artículo en Inglés | MEDLINE | ID: mdl-32058714

RESUMEN

Eleusine indica is a typical xerophytic weed species with a cosmopolitan distribution. It is invasive and highly adaptable to diverse habitats and crops. Due to rice cropping-pattern changes, E indica has become one of the main dominant grass weeds infecting direct-seeding paddy fields. A Chinese E. indica population has evolved multiple-herbicide resistance to cyhalofop-butyl and glyphosate. In this study, the multiple-resistance profile of E. indica to these two different types of herbicides and their resistance mechanisms were investigated. Whole-plant dose-response assays indicated that the multiple-herbicide-resistant (MHR) population exhibited 10.8-fold resistance to cyhalofop-butyl and 3.1-fold resistance to glyphosate compared with the susceptible (S) population. ACCase sequencing revealed that the Asp-2078-Gly mutation was strongly associated with E. indica resistance to cyhalofop-butyl. The MHR plants accumulated less shikimic acid than S plants at 4, 6, and 8 days after glyphosate treatment. In addition, no amino acid substitution in the EPSPS gene was found in MHR plants. Further analysis revealed that the relative expression level of EPSPS in MHR plants was 6-10-fold higher than that in S plants following glyphosate treatment, indicating that EPSPS overexpression may contribute to the glyphosate resistance. Furthermore, the effectiveness of nine post-emergence herbicides against E. indica were evaluated, and one PPO inhibitor pyraclonil was identified as highly effective in controlling the S and MHR E. indica populations.


Asunto(s)
Butanos/farmacología , Eleusine/efectos de los fármacos , Glicina/análogos & derivados , Resistencia a los Herbicidas , Herbicidas/farmacología , Nitrilos/farmacología , Eleusine/genética , Eleusine/metabolismo , Regulación de la Expresión Génica de las Plantas , Glicina/farmacología , Oryza/crecimiento & desarrollo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Malezas/efectos de los fármacos , Malezas/genética , Malezas/metabolismo , Glifosato
14.
ACS Omega ; 5(2): 1246-1253, 2020 Jan 21.
Artículo en Inglés | MEDLINE | ID: mdl-31984282

RESUMEN

As a common kind of food, pepper is well known for its special effects on the physiological state of human individuals. Capsaicin, the main component of pepper, is speculated to be linked with intestinal microorganisms on account of their direct contact. Herein, we first utilized mouse models and 16S rRNA high-throughput sequencing to compare the differences in intestinal flora between mouse groups with and without capsaicin treatment by gavage. The mice in the two groups showed significantly distinct performance in terms of body weight, leukocyte count, fecal humidity, and constituent ratios of intestinal bacteria, such as Faecalibacterium, Akkermansia, Roseburia, Helicobacter, and Bacteroides species. In particular, the Faecalibacterium abundance was the most highly variable among the 5 bacterial genera. Based on statistical analysis and comparison, the variation tendency of body weight, leukocyte count, and fecal humidity was closely related to the bacteria. In conclusion, capsaicin could affect the physiological state of mice by changing the constitution of the intestinal flora.

15.
Pestic Biochem Physiol ; 158: 143-148, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-31378350

RESUMEN

Chinese sprangletop (Leptochloa chinensis (L.) Nees) is one of the most troublesome grass weeds in rice in China. Seven suspected cyhalofop-butyl-resistant L. chinensis populations were collected from different rice fields with a history of cyhalofop-butyl use. The level of resistance and resistance mechanisms in seven populations were studied. Dose-response tests indicated that five populations (JS3, JS4, JS6, JS7 and JS8) had evolved high-level resistance (26.9 to 123.0-fold) to cyhalofop-butyl compared with the susceptible (S) population, and other two populations (JS2 and JS5) were still sensitive to the herbicide. Two acetyl-coenzyme A carboxylase (ACCase) genes were cloned from each population, and three different ACCase mutations (Ile-1781-Leu, Trp-1999-Cys, and Trp-2027-Cys) in ACCase2 gene were determined in different resistant (R) populations. In addition, no resistance-conferring mutations was detected in the R population (JS7), and ACCase gene expression was similar between the S and R populations. Thus, non-target-site resistance mechanisms may be involved in the JS7 population. Moreover, the patterns of cross-resistance of JS6 (Ile-1781-Leu), JS4 (Trp-1999-Cys), JS8 (Trp-2027-Cys), and JS7 (unknown resistance mechanisms) populations to other ACCase-inhibiting herbicides were determined. The JS6 and JS8 populations showed resistance to fenoxaprop-P-ethyl, metamifop, clethodim and pinoxaden, the JS4 population was resistant to fenoxaprop-P-ethyl, metamifop and pinoxaden, and the JS7 population had resistance only to fenoxaprop-P-ethyl and metamifop. These results indicated the diversity of the target-site mutations in ACCase gene of L. chinensis, and provide a better understanding of cross-resistance in L. chinensis, which would be helpful for the management of cyhalofop-butyl-resistant L. chinensis.


Asunto(s)
Acetil-CoA Carboxilasa/metabolismo , Butanos/farmacología , Herbicidas/farmacología , Nitrilos/farmacología , Poaceae/metabolismo , Acetil-CoA Carboxilasa/genética , China , Resistencia a los Herbicidas/genética , Poaceae/efectos de los fármacos
16.
Opt Lett ; 44(12): 3058-3061, 2019 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-31199380

RESUMEN

Tunable silicon nitride nanophotonic resonators are a critical building block for integrated photonic systems in the visible wavelength range. We experimentally demonstrate a thermally tunable polymer-embedded silicon nitride nanobeam cavity with a tuning efficiency of 44 pm/°C and 0.13 nm/mW in the near-visible wavelength range. The large tuning efficiency comes from the high thermo-optic coefficient of the SU-8 polymer and the "air-mode" cavity design, where a large portion of the cavity field is confined inside the polymer region. The demonstrated resonator will enable locally tunable cavity quantum electrodynamic experiments in the silicon nitride platform.

17.
Opt Express ; 27(13): 18673-18682, 2019 Jun 24.
Artículo en Inglés | MEDLINE | ID: mdl-31252806

RESUMEN

Optically active perovskite nanocrystals have shown considerable promise for a myriad of applications, such as single photon source, light-emitting diodes and nanophotonics. Coupling those nanocrystals to photonic micro- and nanostructures will offer additional degrees of freedom to manipulate their optical properties. Herein, we demonstrate the coupling of perovskite nanocrystals to a mechanically robust, poly(methyl-methacrylate) (PMMA)-encapsulated silicon nitride nanobeam photonic crystal cavity at room temperature. As determined from the time-resolved photoluminescence decay measurements, we observed enhanced spontaneous emission from the perovskite nanocrystals by a factor of 1.4, consistent with finite difference time domain simulation. In addition, by varying the concentration of the perovskite nanocrystal in the PMMA layer, the effective index of the layer can be modified, allowing us to tune the cavity mode resonance. Our results show that solution-processable perovskite nanocrystals hold a promising prospect for applications such as on-chip light sources, optoelectronic devices and photonic integrated circuits.

18.
Opt Express ; 27(3): 3609-3616, 2019 Feb 04.
Artículo en Inglés | MEDLINE | ID: mdl-30732377

RESUMEN

We present the design, fabrication, and characterization of a multi-slot photonic crystal (PhC) cavity sensor on the silicon-on-insulator platform. By optimizing the structure of the PhC cavity, most of the light can be distributed in the lower index region; thus, the sensitivity can be dramatically improved. By exposing the cavities to different mass concentrations of NaCl solutions, we obtained that the wavelength shift per refractive index unit (RIU) for the sensor is 586 nm/RIU, which is one of the highest sensitivities achieved in a non-suspended cavity. Furthermore, the size of the sensing region of the reported sensor is only 22.8 µm × 1.5 µm, making the high-sensitivity PhC cavity sensor attractive for the realization of on-chip sensor arrays.

19.
Nano Lett ; 18(11): 6961-6966, 2018 11 14.
Artículo en Inglés | MEDLINE | ID: mdl-30296107

RESUMEN

Ultrathin and flat optical lenses are essential for modern optical imaging, spectroscopy, and energy harvesting. Dielectric metasurfaces comprising nanoscale quasi-periodic resonator arrays are promising for such applications, as they can tailor the phase, amplitude, and polarization of light at subwavelength resolution, enabling multifunctional optical elements. To achieve 2π phase coverage, however, most dielectric metalenses need a thickness comparable to the wavelength, requiring the fabrication of high-aspect-ratio scattering elements. We report ultrathin dielectric metalenses made of van der Waals (vdW) materials, leveraging their high refractive indices and the incomplete phase design approach to achieve device thicknesses down to ∼λ/10, operating at infrared and visible wavelengths. These materials have generated strong interest in recent years due to their advantageous optoelectronic properties. Using vdW metalenses, we demonstrate near-diffraction-limited focusing and imaging and exploit their layered nature to transfer the fabricated metalenses onto flexible substrates to show strain-induced tunable focusing. Our work enables further downscaling of optical elements and opportunities for the integration of metasurface optics in ultraminiature optoelectronic systems.

20.
Nano Lett ; 18(10): 6404-6410, 2018 10 10.
Artículo en Inglés | MEDLINE | ID: mdl-30251868

RESUMEN

Engineering an array of precisely located cavity-coupled active media poses a major experimental challenge in the field of hybrid integrated photonics. We deterministically position solution-processed colloidal quantum dots (QDs) on high quality (Q)-factor silicon nitride nanobeam cavities and demonstrate light-matter coupling. By lithographically defining a window on top of an encapsulated cavity that is cladded in a polymer resist, and spin coating the QD solution, we can precisely control the placement of the QDs, which subsequently couple to the cavity. We show rudimentary control of the number of QDs coupled to the cavity by modifying the size of the window. Furthermore, we demonstrate Purcell enhancement and saturable photoluminescence in this QD-cavity platform. Finally, we deterministically position QDs on a photonic molecule and observe QD-coupled cavity supermodes. Our results pave the way for precisely controlling the number of QDs coupled to a cavity by engineering the window size, the QD dimension, and the solution chemistry and will allow advanced studies in cavity enhanced single photon emission, ultralow power nonlinear optics, and quantum many-body simulations with interacting photons.

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