In this work, we propose a photonic quasicrystal waveguide, which contains a hollow core surrounded by coaxial dielectric quasiperiodic multilayer. Due to the self-similarity in the cladding structure, multiple omnidirectional photonic band gaps (PBGs) exist in the waveguide. The light waves with the frequencies within the omnidirectional PBGs are totally reflected, thereafter, the transport of multimodes is achieved in the quasiperiodic waveguide. Further, it is shown that the centre frequency and the width of the omnidirectional PBG can be tuned by the refractive indexes or the generations of the quasiperiodic sequence in the cladding multilayer. As a consequence, both the quality factor and the confinement performance of the waveguide can be significantly enhanced by decreasing the width of the omnidirectional PBGs. The investigations make it possible to design miniaturized multifunctional optical devices, such as on-chip narrowband waveguide-based filters and laser resonators. Copyright © 2013 American Scientific Publishers All rights reserved.

Hu Qing;Sun Liu-Yang;Xu Di-Hu;Zhou Yu;Peng Ru-Wen;Wang Mu

Journal of Nanoscience and Nanotechnology

2013

We report here the experimental observations that the tip topography of ZnO nano-prisms sensitively depends on the percentage of oxygen in the flux of the carrying gas in vapor growth. At a relatively high oxygen concentration, a number of thin filaments can be nucleated atop nano-prisms, forming a unique fish-spear-like multi-tip morphology. The length and density of the "spear tines" depend on the flux of the carrying gas. The field emission properties of the nanorod array with different tip morphology are investigated. The structures with longer and denser spear tines possess lower turn-on electric field and higher electric current density. The cathodoluminescence properties of the ZnO nano-prisms have also been studied. The luminescence related to defects in multi-tip nano-prisms possesses the strongest intensity, and the nanorod without any tine structure possesses the lowest defect luminescence intensity. The intrinsic luminescence of ZnO around 385 nm, however, has the opposite tendency. We suggest that our observation is inspiring in optimizing the emission properties of the nanowire devices. © Copyright EPLA, 2013.

Liu Ming;Meng Cong;Xue Zheng-Hong;Xiong Xiang;Shu Da-Jun;Peng Ru-Wen;Wang Mu;Wu Qiang;Hu Zheng

Epl

2013

Jiang Shang-Chi;Xiong Xiang;Sarriugarte Paulo;Jiang Sheng-Wei;Yin Xiao-Bo;Wang Yuan;Peng Ru-Wen;Wu Di;Hillenbrand Rainer;Zhang Xiang;Wang Mu

Physical Review B Condensed Matter and Materials Physics

2013

We report a highly asymmetric magnetoresistance (MR) bias dependence, with the inverse MR peaking at a negative bias and a sign reversal occurring at a positive bias in prototypical La0.7Sr0.3MnO3 (LSMO)/Alq3/Co organic spin valve (OSV) with a tunnel barrier between LSMO and Alq3. This behavior is in strong contrast with the commonly found inverse MR in entire bias range for LSMO/Alq3/Co OSVs. The MR bias voltage dependence is independent on the type of the tunnel barrier, either SrTiO3 or Al2O3. Together with first-principle calculations, we demonstrate that the strongly hybridized Co d-states with Alq3 molecules at the interface are responsible for the efficient d-states spin injection and the observed MR bias dependence is originated from the energy dependent density of states of Co d-states. These findings open up new possibilities to engineer interfacial bonding between ferromagnetic materials and a wide variety of molecule selections for the desired spin transport properties. © 2014 IOP Publishing and Deutsche Physikalische Gesellschaft.

Jiang S. W.;Shu D. J.;Lin L.;Shi Y. J.;Ding H. F.;Du J.;Wang M.;Wu D.;Shi J.

New Journal of Physics

2014

© 2014 Author(s). In this letter, we report a full-metallic broadband wave plate assembled by standing metallic L-shaped stereostructures (LSSs). We show that with an array of LSSs, high polarization conversion ratio is achieved within a broad frequency band. Moreover, by rotating the orientation of the array of LSSs, the electric components of the reflection beam in two orthogonal directions and their phase difference can be independently tuned. In this way, all the polarization states on the Poincaré sphere can be realized. As examples, the functionalities of a quarter wave plate and a half wave plate are experimentally demonstrated with both reflection spectra and focal-plane-array imaging. Our designing provides a unique approach in realizing the broadband wave plate to manipulate the polarization state of light.

Xiong Xiang;Hu Yuan-Sheng;Jiang Shang-Chi;Hu Yu-Hui;Fan Ren-Hao;Ma Guo-Bin;Shu Da-Jun;Peng Ru-Wen;Wang Mu

Applied Physics Letters

2014

© 2016 AIP Publishing LLC. We report on van der Waals epitaxy of single-crystalline α-MoO3 sheets with single-unit-cell thickness on the mica substrate. The crystalline lattice structure, growth habits, and Raman spectra of the grown α-MoO3 sheets are analyzed. The anisotropic growth of α-MoO3 sheets can be understood by period bond chains theory. Unlike monolayer MoS2 or graphene, Raman spectra of α-MoO3 do not possess frequency shift from bulk crystal to single-unit-cell layer. The relative intensities of two Raman modes (Ag) at 159 and 818 cm^-1 are sensitive to the polarization of incident light. This scenario provides a quick approach to determine the lattice orientation of α-MoO3 crystals. Our studies indicate that van der Waals epitaxial growth is a simple and effective way to fabricate high-quality ultrathin α-MoO3 sheets for physical property investigations and potential applications.

Wang Di;Li Jing-Ning;Zhou Yu;Xu Di-Hu;Xiong Xiang;Peng Ru-Wen;Wang Mu

Applied Physics Letters

2016

© 2015 Optical Society of America. In this work, we theoretically study the cavity modes with transverse orbital angular momentum in metamaterial ring based on transformation optics. The metamaterial ring is designed to transform the straight trajectory of light into the circulating one by enlarging the azimuthal angle, effectively presenting the modes with transverse orbital angular momentum. The simulation results confirm the theoretical predictions, which state that the transverse orbital angular momentum of the mode not only depends on the frequency of the incident light, but also depends on the transformation scale of the azimuthal angle. Because energy dissipation inevitably reduces the field amplitude of the modes, the confined electromagnetic energy and the quality factor of the modes inside the ring are also studied in order to evaluate the stability of those cavity modes. The results show that the metamaterial ring can effectively confine light with a high quality factor and maintain steady modes with the orbital angular momentum, even if the dimension of the ring is much smaller than the wavelength of the incident light. This technique for exploiting the modes with optical transverse orbital angular momentum may provides a unique platform for applications related to micromanipulation.

Wu H. W.;Wang F.;Dong Y. Q.;Shu F. Z.;Zhang K.;Peng R. W.;Xiong X.;Wang Mu

Optics Express

2015

© 2016 the Owner Societies. The influence of externally applied strain on water adsorption and dissociation on a defect-free rutile TiO2(110) surface is studied by using first-principles calculations. We found that while compressive strain makes water adsorption and dissociation less favorable, tensile strain increases the energy gain of water adsorption, and decreases the energy cost of water dissociation. Specifically, dissociative water becomes more stable than molecular water when an 8% tensile in-plane strain is applied. Moreover, the dissociation barrier decreases with increasing strain more rapidly for more isolated water. The rate of decrease of this barrier for nearly isolated water is 0.017 eV per 1% biaxial strain. This demonstrates that applying strain is a possible way to engineer the surface adsorption and dissociation of water on a TiO2(110) surface, and therefore engineer the relevant surface reactivity.

Yang Long;Shu Da-Jun;Li Shao-Chun;Wang Mu

Physical Chemistry Chemical Physics

2016

© 2017 Optical Society of America. Monolayer MoS 2 is an emerging two-dimensional semiconductor that has seen wide applications in optoelectronic and light-emitting devices. Here we report on the antenna-enhanced spontaneous emission of monolayer MoS 2 , which has weak absorbance and low intrinsic quantum yield. The ultrathin silver platelet antennas we use can both increase the absorption cross-section and improve the transmission efficiency via controlling the optical field at nanometer scale. Experimental results indicate the photoluminescence enhancement can reach 4 times, which is also supported by numerical analysis of both excitation and emission processes with respect to the thickness of spacer layer. This ultrathin structure can facilitate the development of on-chip emitters and valley-based devices, especially in cases of large area sample or flexible substrate.

Yang Yingyi;Tan Zheng Jie;Fang Nicholas X.;Wang Di;Xiong Xiang;Wang Mu;Peng Ruwen

Optics Express

2017

© 2017 Optical Society of America. In this work, we demonstrate polarization-dependent strong coupling between surface plasmon polaritons (SPPs) and excitons in the J -aggregates-attached aperture array. It is shown that the excitons strongly couple with the polarization-dependent SPPs, and Rabi splittings are consequently observed. As a result, the polarization-dependent polariton bands are generated in the system. Increasing the incident angle, the polaritons disperse to higher energies under transverse-electric illumination, while the polaritons disperse to lower energies under transverse-magnetic illumination. Therefore, at different polarization incidence, we experimentally achieve distinct polaritons with opposite dispersion directions. In this way, tuning the polarization of the incident light, we can excite different polaritons whose energy propagates to different directions. Furthermore, by retrieving the mixing fractions of the components in these polariton bands, we find that the dispersion properties of the polaritons are inherited from both the SPPs and the excitons. Our investigation may inspire related studies on tunable photon–exciton interactions and achieve some potential applications on active polariton devices.

Zhang Kun;Chen Tian-Yong;Shi Wen-Bo;Li Cheng-Yao;Fan Ren-Hao;Wang Qian-Jin;Peng Ru-Wen;Wang Mu

Optics Letters

2017