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1.
Opt Express ; 27(5): 7627-7628, 2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-30876324

RESUMO

Photonic technologies that support the low cost manufacturing needed for automotive sensors have experienced explosive developments in recent years. To date most commercially available lidar system have been direct detection time-of-flight (ToF) sensors operating at 905 nm using mechanical mirrors for beam steering. However, these sensors suffer from important drawbacks. One issue is eye-safety, which limits maximum laser powers and hence operating range. Direct detection systems must also content with potential interference issues when lots of cars operate lidar systems simultaneously. In addition, mechanical scanners are frequently bulky and may be difficult to integrate within the form factors allowed by modern vehicles.

2.
Org Lett ; 20(22): 6984-6989, 2018 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-30398887

RESUMO

A visible-light-mediated radical tandem cyclization of ortho-isocyano-α-bromo cinnamates to 2-substituted indole-3-glyoxylates is achieved by formation of both C-C/C-S and C-O bonds. The reaction proceeds through a hitherto unprecedented bromine- or methoxy-group-promoted umpolung back electron transfer from an α-carbonyl radical to the photocatalyst. This method allows preparation of diverse 2-arylated or 2-thioarylated indole-3-glyoxylates. The glyoxylate group installed in the products can be utilized for several biologically relevant manipulations.

4.
ACS Appl Mater Interfaces ; 10(37): 30919-30924, 2018 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-30160097

RESUMO

Raising the light absorption of the photoactive layer in polymer solar cells (PSCs) without increasing the layer thickness is desirable but challenging because of the low carrier mobility of organic materials. Herein, we used the coupled localized surface plasmon resonance of heterostructured Au-Cu2- xS nanocrystals (NCs) to improve the light-trapping capability of the photoactive layer of PSCs. Broadband light absorption and a considerable improvement of the power conversion efficiency were obtained when the photoactive layer was doped with a tiny amount of NCs. This can be explicated by the enhanced near-field intensity and broadband scattering properties of added NCs.

5.
Opt Express ; 25(22): 27715-27723, 2017 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-29092242

RESUMO

We report InAs/InGaAs quantum dot (QD) waveguide photodetectors (PD) monolithically grown on silicon substrates. A high-crystalline quality GaAs-on-Si template was achieved by aspect ratio trapping together with the combined effects of cyclic thermal annealing and strain-balancing layer stacks. An ultra-low dark current of 0.8 nA and an internal responsivity of 0.9 A/W were measured in the O band. We also report, to the best of our knowledge, the first characterization of high-speed performance and the first demonstration of the on-chip photodetection for this QD-on-silicon system. The monolithically integrated waveguide PD shares the same platform as the previously demonstrated micro-ring lasers and can thus be integrated with laser sources for power monitors or amplifiers for pre-amplified receivers.

6.
Zhongguo Yi Xue Ke Xue Yuan Xue Bao ; 39(5): 629-636, 2017 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-29125104

RESUMO

Objective To investigate the polymorphisms of 23 Y-STR loci in a Han population in Jiangsu province. Methods Blood samples were collected from 4821 unrelated healthy Han males in Jiangsu province. DNA templates were amplified by PowerPlex Y23 kit,and the amplification products were detected by 3500xL genetic analyzer. Then,we calculated the allele frequencies and gene diversities respectively,as well as the haplotype frequencies and haplotype diversities. Results The gene diversity of these 23 Y-STR loci ranged 0.4099-0.9696. A total of 4781 haplotypes were detected,of which 4743 were found once. The haplotype diversity was 0.99999812. Conclusion The 23 Y-STR loci used in this study are highly polymorphic in Han individuals in Jiangsu province and therefore suitable for population genetic study and forensic individual identification.

7.
Nat Commun ; 8(1): 35, 2017 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-28652572

RESUMO

Atomically thin lateral heterostructures based on transition metal dichalcogenides have recently been demonstrated. In monolayer transition metal dichalcogenides, exciton energy transfer is typically limited to a short range (~1 µm), and additional losses may be incurred at the interfacial regions of a lateral heterostructure. To overcome these challenges, here we experimentally implement a planar metal-oxide-semiconductor structure by placing a WS2/MoS2 monolayer heterostructure on top of an Al2O3-capped Ag single-crystalline plate. We find that the exciton energy transfer range can be extended to tens of microns in the hybrid structure mediated by an exciton-surface plasmon polariton-exciton conversion mechanism, allowing cascaded exciton energy transfer from one transition metal dichalcogenides region supporting high-energy exciton resonance to a different transition metal dichalcogenides region in the lateral heterostructure with low-energy exciton resonance. The realized planar hybrid structure combines two-dimensional light-emitting materials with planar plasmonic waveguides and offers great potential for developing integrated photonic and plasmonic devices.Exciton energy transfer in monolayer transition metal dichalcogenides is limited to short distances. Here, Shi et al. fabricate a planar metal-oxide-semiconductor structure and show that exciton energy transfer can be extended to tens of microns, mediated by an exciton-surface-plasmon-polariton-exciton conversion mechanism.

8.
Nat Commun ; 8: 14180, 2017 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-28120825

RESUMO

Many naturally occurring biomolecules, such as amino acids, sugars and nucleotides, are inherently chiral. Enantiomers, a pair of chiral isomers with opposite handedness, often exhibit similar physical and chemical properties due to their identical functional groups and composition, yet show different toxicity to cells. Detecting enantiomers in small quantities has an essential role in drug development to eliminate their unwanted side effects. Here we exploit strong chiral interactions with plasmonic metamaterials with specifically designed optical response to sense chiral molecules down to zeptomole levels, several orders of magnitude smaller than what is typically detectable with conventional circular dichroism spectroscopy. In particular, the measured spectra reveal opposite signs in the spectral regime directly associated with different chiral responses, providing a way to univocally assess molecular chirality. Our work introduces an ultrathin, planarized nanophotonic interface to sense chiral molecules with inherently weak circular dichroism at visible and near-infrared frequencies.

9.
Opt Express ; 25(3): 2422-2431, 2017 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-29519088

RESUMO

We demonstrate a photonic microwave generator on the heterogeneous silicon-InP platform. Waveguide photodiodes with a 3 dB bandwidth of 65 GHz and 0.4 A/W responsivity are integrated with lasers that tune over 42 nm with less than 150 kHz linewidth. Microwave signal generation from 1 to 112 GHz is achieved.

10.
Nano Lett ; 16(7): 4322-8, 2016 07 13.
Artigo em Inglês | MEDLINE | ID: mdl-27332701

RESUMO

The smallness of natural molecules and atoms with respect to the wavelength of light imposes severe limits on the nature of their optical response. For example, the well-known argument of Landau and Lifshitz and its recent extensions that include chiral molecules show that the electric dipole response dominates over the magneto-electric (bianisotropic) and an even smaller magnetic dipole optical response for all natural materials. Here, we experimentally demonstrate that both these responses can be greatly enhanced in plasmonic nanoclusters. Using atomic force microscopy nanomanipulation technique, we assemble a plasmonic metamolecule that is designed for strong and simultaneous optical magnetic and magneto-electric excitation. Angle-dependent scattering spectroscopy is used to disentangle the two responses and to demonstrate that their constructive/destructive interplay causes strong directional scattering asymmetry. This asymmetry is used to extract both magneto-electric and magnetic dipole responses and to demonstrate their enhancement in comparison to ordinary atomistic materials.

11.
J Org Chem ; 81(9): 3568-75, 2016 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-27031001

RESUMO

A new method was developed to synthesize N(2)-alkyl-substituted 1,2,3-triazole through N-iodosuccinimide (NIS) mediated iodofuctionalization reaction of the alkene group with bi-, mono-, and unsubstituted NH-1,2,3-triazoles. The favored N-1 type hydrogen bond between the iodonium ion intermediate and 1,2,3-triazole was supposed to be generated, which gave the desired N(2)-alkyl triazole with a high N(2)-selectivity.

12.
J Org Chem ; 80(24): 12733-9, 2015 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-26599304

RESUMO

A new method was developed to synthesize polyfunctionalized dihydrofuran and tetrahydrofuran derivatives from the three-component [2 + 2 + 1] cycloaddition of the diazoesters with aryl/alkenyl aldehydes and alkyne/olefin dipolarophiles by using a Ag(I) N-heterocyclic carbene complex as the catalyst. A carbonyl ylide intermediate was generated, which undertook an endo-type 1,3-dipolar cycloaddition to provide the desired dihydro-/tetrahydrofurans in high regio- and diastereoselectivities by using α-aryl or α-alkenyl diazoesters.

13.
Opt Express ; 23(15): 19535-41, 2015 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-26367611

RESUMO

Asymmetric transmission (AT) effect has attracted great interest in recent years, due to its potential application in integrated photonics from GHz to optical frequency. To realize AT effect, numerous metamaterials have been proposed, mainly based on the chirality of the structure. In this paper, we demonstrate that achiral metamaterials can also have AT effect. Furthermore, it is shown that modal conversion is more essential than chirality to achieve AT effect. In particular, we have proposed a mirror symmetric metamaterial with broadband high efficiency AT effect for circular polarization wave operating at THz region. With further optimization of the unit cell, >80% of the central frequency bandwidth and average 74.05 (maximum150) transmission ratio can be obtained. The idea demonstrated here can also be applied to other frequency regions.

14.
Proc Natl Acad Sci U S A ; 112(40): 12288-92, 2015 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-26372957

RESUMO

Plasmonic cavities represent a promising platform for controlling light-matter interaction due to their exceptionally small mode volume and high density of photonic states. Using plasmonic cavities for enhancing light's coupling to individual two-level systems, such as single semiconductor quantum dots (QD), is particularly desirable for exploring cavity quantum electrodynamic (QED) effects and using them in quantum information applications. The lack of experimental progress in this area is in part due to the difficulty of precisely placing a QD within nanometers of the plasmonic cavity. Here, we study the simplest plasmonic cavity in the form of a spherical metallic nanoparticle (MNP). By controllably positioning a semiconductor QD in the close proximity of the MNP cavity via atomic force microscope (AFM) manipulation, the scattering spectrum of the MNP is dramatically modified due to Fano interference between the classical plasmonic resonance of the MNP and the quantized exciton resonance in the QD. Moreover, our experiment demonstrates that a single two-level system can render a spherical MNP strongly anisotropic. These findings represent an important step toward realizing quantum plasmonic devices.

15.
Nat Commun ; 5: 3896, 2014 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-24871450

RESUMO

A key element enabling the microelectronic technology advances of the past decades has been the conceptualization of complex circuits with versatile functionalities as being composed of the proper combination of basic 'lumped' circuit elements (for example, inductors and capacitors). In contrast, modern nanophotonic systems are still far from a similar level of sophistication, partially because of the lack of modularization of their response in terms of basic building blocks. Here we demonstrate the design, assembly and characterization of relatively complex photonic nanocircuits by accurately positioning a number of metallic and dielectric nanoparticles acting as modular lumped elements. The nanoparticle clusters produce the desired spectral response described by simple circuit rules and are shown to be dynamically reconfigurable by modifying the direction or polarization of impinging signals. Our work represents an important step towards extending the powerful modular design tools of electronic circuits into nanophotonic systems.

16.
Opt Lett ; 39(1): 5-8, 2014 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-24365807

RESUMO

A series of sequentially cascade-pumped random lasers is reported. It consists of three random lasers in which the Ag-Au bimetallic porous nanowires play the role of scatterers, and the gain materials are coumarin 440 (C440), coumarin 153 (C153), and rhodamine 6G (R6G), respectively. The random laser with C440 is first pumped by a 355 nm pulsed laser. The emission of C440 pumps the C153, and the emission of C153 pumps the R6G sequentially. Low-threshold coherent emissions from the three random lasers are observed. The cascade-pumped random lasers can be achieved easily with low cost and can be used in applications conveniently.

17.
Adv Mater ; 26(9): 1439-45, 2014 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-24307266

RESUMO

Three-dimensional optical metamaterials based on multilayers typically rely on critical vertical alignment to achieve the desired functionality. Here the conditions under which three-dimensional metamaterials with different functionalities may be realized without constraints on alignment are analyzed and demonstrated experimentally. This study demonstrates that the release of alignment constraints for multilayered metamaterials is allowed, while their anomalous interaction with light is preserved.

18.
Opt Express ; 21(12): 14109-19, 2013 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-23787601

RESUMO

We demonstrate that a near-single-cycle photonic millimeter-wave short-pulse generator at W-band is capable to provide high spatial resolution three-dimensional (3-D) radar imaging. A preliminary study indicates that 3-D radar images with a state-of-the-art ranging resolution of around 1.2 cm at the W-band can be achieved.


Assuntos
Imagem Tridimensional/instrumentação , Radar/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Micro-Ondas
19.
Opt Express ; 21(9): 11475-81, 2013 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-23670004

RESUMO

A high-performance photonic sweeping-frequency (chirped) radio-frequency (RF) generator has been demonstrated. By use of a novel wavelength sweeping distributed-feedback (DFB) laser, which is operated based on the linewidth enhancement effect, a fixed wavelength narrow-linewidth DFB laser, and a wideband (dc to 50 GHz) photodiode module for the hetero-dyne beating RF signal generation, a very clear chirped RF waveform can be captured by a fast real-time scope. A very-high frequency sweeping rate (10.3 GHz/µs) with an ultra-wide RF frequency sweeping range (~40 GHz) have been demonstrated. The high-repeatability (~97%) in sweeping frequency has been verified by analyzing tens of repetitive chirped waveforms.


Assuntos
Lasers , Oscilometria/instrumentação , Telecomunicações/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Retroalimentação
20.
Opt Express ; 21(25): 30746-54, 2013 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-24514651

RESUMO

A scheme for constructing the electromagnetic localization structure (ELS) is proposed based on the transformation optics. The ELS may have a free space cavity of cylindrical or arbitrary shapes enclosed by a metamaterials layer. The electromagnetic field can be localized in the free space cavity with no energy leaked in the metamaterials layer and the eigenmodes of the cavity is continuous, which are novel properties that the reported metamaterials ELSs could not realize. The principle and feasibility of the scheme are described in detail through the cylindrical ELS. It is shown that all the material parameters of the designed cylindrical ELS change smoothly with finite values. Therefore it is more practical than the reported metamaterials ELS. In the designing of ELS, the space transformation function was solved via solving the Laplace equation with the Dirichlet boundary condition, which makes it possible to design the ELS of arbitrary shape. The viability of the ELS with arbitrary shape is analyzed and demonstrated by the full-wave numerical simulations.

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