High-Efficiency Fabrication of Geometric Phase Elements by Femtosecond-Laser Direct Writing.

The nanoresolution of geometric phase elements for visible wavelengths calls for a flexible technology with high throughout and free from vacuum. In this article, we propose a high-efficiency and simple manufacturing method for the fabrication of geometric phase elements with femtosecond-laser direct writing (FsLDW) and thermal annealing by combining the advantages of high-efficiency processing and thermal smoothing effect. By using a femtosecond laser at a wavelength of 343 nm and a circular polarization, free-form nanogratings with a period of 300 nm and 170-nm-wide grooves were obtained in 50 s by laser direct ablation at a speed of 5 mm/s in a non-vacuum environment. After fine-tuning through a hot-annealing process, the surface morphology of the geometric phase element was clearly improved. With this technology, we fabricated blazed gratings, metasurface lens, vortex Q-plates and "M" holograms and confirmed the design performance by analyzing their phases at the wavelength of 808 nm. The efficiency and capabilities of our proposed method can pave the possible way to fabricate geometric phase elements with essentially low loss, high-temperature resistance, high phase gradients and novel polarization functionality for potentially wide applications.

Platelet count on preoperative day 1 predicts the long-term responses to laparoscopic splenectomy for Chinese patients with medically refractory idiopathic thrombocytopenic purpura.

BACKGROUND: Laparoscopic splenectomy (LS) is regarded as a second-line treatment for medically refractory idiopathic thrombocytopenic purpura (ITP), but the predictive factors for the long-term postoperative responses to ITP are still a matter of debate. We aimed to investigate the factors that can predict the long-term response after LS for Chinese patients with medically refractory ITP. METHODS: From January 2011 to September 2016, 78 Chinese patients with ITP who underwent LS were retrospectively analyzed. Twelve parameters were analyzed by univariate and multivariate methods. RESULTS: Univariate analysis revealed that platelet count on preoperative day (PRD) 1 (P < 0.001) and operative time (P = 0.011) were significantly associated with long-term response of ITP after LS. Multivariate analysis revealed that platelet count on PRD 1 was a predictive factor of long-term response (P < 0.001). Furthermore, a long-term, stable response of platelet count on PRD 1 of > 30.0 × 109/L was easier to achieve than a platelet count on PRD 1 ≤ 30.0 × 109/L after LS for ITP. CONCLUSIONS: LS is a valuable and effective option in the treatment of medically refractory ITP. Platelet count on PRD 1 is an independent predicting factor for long-term response after LS for Chinese patients with ITP.

Integrated photonics with programmable non-volatile memory.

Silicon photonics integrated circuits (Si-PIC) with well-established active and passive building elements are progressing towards large-scale commercialization in optical communications and high speed optical interconnects applications. However, current Si-PICs do not have memory capabilities, in particular, the non-volatile memory functionality for energy efficient data storage. Here, we propose an electrically programmable, multi-level non-volatile photonics memory cell (PMC) fabricated by standard complementary-metal-oxide-semiconductor (CMOS) compatible processes. A micro-ring resonator (MRR) was built using the PMC to optically read the memory states. Switching energy smaller than 20 pJ was achieved. Additionally, a MRR memory array was employed to demonstrate a four-bit memory read capacity. Theoretically, this can be increased up to ~400 times using a 100 nm free spectral range broadband light source. The fundamental concept of this design provides a route to eliminate the von Neumann bottleneck. The energy-efficient optical storage can complement on-chip optical interconnects for neutral networking, memory input/output interfaces and other computational intensive applications.

Measurement of Two-Photon Absorption Cross Section of Metal Ions by a Mass Sedimentation Approach.

The photo-reduction of metal ions in solution induced by femtosecond laser is an important and novel method for fabricating three-dimensional metal microstructures. However, the nonlinear absorption cross section of metal ions remains unknown because its measurement is difficult. In the present study, a method based on Two-Photon Excited Sedimentation (TPES) is proposed to measure the two-photon absorption cross section (TPACS) of metal ions in solution. The power-squared dependence of the amount of sediment on the excitation intensity was confirmed, revealing that 800 nm femtosecond laser induced reduction of metal ions was a two photon absorption process. We believe that the proposed method may be applied to measure the TPACS of several metal ions, thereby opening a new avenue towards future analysis of two-photon absorption materials.

Hybrid III-V/silicon laser with laterally coupled Bragg grating.

In this paper, we demonstrate a compact electrically pumped distributed-feedback hybrid III-V/silicon laser with laterally coupled Bragg grating for the first time to the best of our knowledge. The hybrid laser structure consists of AlGaInAs/InP multi-quantum-well gain layers on top of a laterally corrugated silicon waveguide patterned on a silicon on insulator (SOI) substrate. A pair of surface couplers is integrated at the two ends of the silicon waveguide for the optical coupling and characterization of the ouput light. Single wavelength emission of ~1.55µm with a side-mode-suppression- ratio larger than 20dB and low threshold current density of 1.54kA/cm(2) were achieved for the device under pulsed operation at 20 °C.

Interface potential sensing from adsorption of human serum albumin (HSA) on carbon nanotube (CNT) monitored by zero current potentiometry for HSA determination.

In this work, the adsorption of human serum albumin (HSA) on the bare multiwall carbon nanotube (MWNT) was investigated by a new electrochemical method, termed as zero current potentiometry. For this, a MWNT strip was prepared by directly adhering MWNTs on the transparent adhesive tape surface. Moreover, when HSA adsorbed onto MWNT at the MWNT/solution interface, an interface potential Ψ yielded. The interface potential Ψ as the zero current potential Ezcp simply related to it was monitored by zero current potentiometry. The relationship between the zero current potential Ezcp, the HSA concentration and others was established in simple stoichiometric relation. Based on this, both the adsorption of HSA on MWNT and the HSA determination can be studied. For the HSA determination, the theoretic conclusion consisted with experimental results. The zero current potential Ezcp was proportional to the HSA concentration in the range of 2.8 × 10(-8) - 3.4 × 10(-7)M with the limit of detection 2 × 10(-8)M. The linear regression equation was Ezcp/V (vs, SCE) = (0.159 ± 0.01) + (0.358 ± 0.02) × 10(6)CHSA (µM). This determination was fast, high sensitive and good selective.

Spectral engineering by flexible tunings of optical Tamm states and Fabry-Perot cavity resonance.

We present a design for spectral engineering in a metal dual distributed Bragg reflector (DBR)-based structure. Optical Tamm states and Fabry-Perot cavity mode, dual windows for light-matter interaction enhancement, can be excited simultaneously and tuned flexibly, including their respective bandwidth and resonant wavelength, due to the variable reflection phase from the outer DBR's internal surface. The design can find applications in solar cells for light trappings. Via calculations of overall absorptivity, the proposed simpler dual-states-based scheme is demonstrated to be almost as effective as the coherent-light-trapping scheme, owing to the dual-states-induced broader-band absorption enhancement.

Fabrication and characterization of Ag film with sub-nanometer surface roughness as a flexible cathode for inverted top-emitting organic light-emitting devices.

An ultra-smooth Ag film with sub-nanometer surface roughness on a flexible substrate has been fabricated by a template-stripping process and its effect on the carrier injection and transport in organic light-emitting devices (OLEDs) has been investigated. The use of the ultra-smooth Ag film as an electrode results in both enhanced carried injection due to the improved contact between the electrode and the organic layer and enhanced carrier transport due to the larger grain size of the deposited organic layer on it. The ultra-smooth Ag film on the flexible substrate has been applied in inverted top-emitting OLEDs (ITOLEDs) as cathode, which exhibit improved efficiency due to the enhanced electron injection and transport. The maximum current efficiency of the ITOLEDs on the flexible substrate is 9.72 cd A(-1), whereas it is 6.03 cd A(-1) for the devices on the conventional Si substrate, which corresponds to about a 62% enhancement. Moreover, the flexible ITOLEDs keep their good performance under a small bending radius and after repeated bending.

Complex three-dimensional polymer-metal core-shell structures towards emission control.

We report the fabrication of three-dimensional periodic metal nickel nanostructures achieved by the combination of femtosecond laser-induced two-photon polymerization and electroless plating technology. We can control the deposition speed of 10 nm per second by adjusting the reaction time. The thermal stability is good under 500 °C for the three-dimensional graphite-lattice polymer structure with 200 nm nickel film. Optical reflectivity and thermal emission measurements under 550 °C showed that the fabricated metallic structure was thermally excited and emitted light at λ = 4.50, 4.95 µm. The emission peak wavelengths agree with the absorption peaks. These data demonstrate that creating metallic photonic crystals by incorporation of metals to laser-fabricated templates is a simple and cost-efficient method. The emitters can work at such low temperatures, which is more important for realistic operation in applications.

Omnidirectional emission from top-emitting organic light-emitting devices with microstructured cavity.

We demonstrate optimized viewing-angle characteristics from top-emitting organic light-emitting devices by integrating a periodic microstructure into the cavity. A holographic lithography technique combined with filling process of the groove by spin coating of a polymer film has been employed to enable its periodically and gradually changed cavity length and suppress the viewing-angle dependence of the peak emission wavelength and intensity. The theoretical and experimental results support that the proposed microstructured cavity can resolve the angular-dependence effect in a very simple and effective way, and a desired omnidirectional emission has been obtained.

Nanoporous TiO2/polyion thin-film-coated long-period grating sensors for the direct measurement of low-molecular-weight analytes.

We present novel nanoporous TiO(2)/polyion thin-film-coated long-period fiber grating (LPFG) sensors for the direct measurement of low-molecular-weight chemicals by monitoring the resonance wavelength shift. The hybrid overlay films are prepared by a simple layer-by-layer deposition approach, which is mainly based on the electrostatic interaction of TiO(2) nanoparticles and polyions. By the alternate immersion of LPFG into dispersions of TiO(2) nanoparticles and polyions, respectively, the so-formed TiO(2)/polyion thin film exhibits a unique nanoporous internal structure and has a relative higher refractive index than LPFG cladding. In particular, the porosity of the thin film reduces the diffusion coefficient and enhances the permeability retention of low-molecular-weight analytes within the porous film. The increases in the refractive index of the LPFG overlay results in a distinguished modulation of the resonance wavelength. Therefore, the detection sensitivity of LPFG sensors has been greatly improved, according to theoretical simulation. After the structure of the TiO(2)/polyion thin film was optimized, glucose solutions as an example with a low concentration of 10(-7) M was easily detected and monitored at room temperature.

Grating amplitude effect on electroluminescence enhancement of corrugated organic light-emitting devices.

We report grating amplitude dependence of electroluminescence (EL) in organic light-emitting devices with one-dimensional corrugated structure. Our proposed devices can emit light from both the top silver and bottom quartz side, and both exhibit amplitude-dependence EL enhancement. The effect of grating amplitude on the EL intensity has been studied experimentally and numerically to find out the optimal grating amplitude for the greatest EL enhancement. We deduce from the numerical simulations and experimental results that surface plasmon-polariton modes and waveguide modes are coupled out of the corrugated devices efficiently at the optimal amplitude; therefore, higher efficiency of light extraction could be realized.

Cathodic electrochemiluminescence of the peroxydisulphate-ciprofloxacin system and its analytical applications.

The cathodic electrochemiluminescence (ECL) of peroxydisulphate (S(2)O(8)(2-))-ciprofloxacin (CPF) system at a wax-impregnated graphite electrode was studied. When CPF was absent, S(2)O(8)(2-) was electrochemically reduced to sulphate free radical (SO(4)(•-)), and dissolved oxygen absorbed on the electrode surface was reduced to protonated superoxide anion radical (HO(2)(•)). The HO(2)(•) was oxidized by SO(4)(•-) to produce molecular oxygen in both singlet and triplet states. Some of the singlet molecular oxygen ((1)O(2)) further combined through collision to be an energy-rich precursor singlet molecular oxygen pair ((1)O(2))(2). A weak ECL was produced when (1)O(2) or ((1)O(2))(2) was converted to ground-state molecular oxygen ((3)O(2)). When CPF was present, a stronger ECL was produced, which originated from two emitting species. The main emitting species was excited state CPF (CPF*), which was produced by accepting energy from ((1)O(2))(2). The other emitting species was excited singlet molecular oxygen pair [((1)O(2))(2)*], which originated from the chemical oxidation of CPF by SO(4)(•-) and dissolved oxygen. Based on the stronger ECL phenomenon, an ECL method for the determination of either S(2)O(8)(2-) or CPF was proposed. The proposed ECL method has been applied to the determination of CPF in pharmaceutical preparations.

Interaction of calf thymus dsDNA with anti-tumor drug tamoxifen studied by zero current potentiometry.

Since the electrochemical oxidation peaks of both DNA and anti-tumor drug tamoxifen (TAM) overlapped with each other, the known electrochemical methods were limited in the study of the interactions between DNA and TAM. In this paper, zero current potentiometry, a new electrochemical method, was used to study the interaction of calf thymus dsDNA with TAM. The dsDNA was immobilized on the surface of carbon paste (dsDNA/CP). The dsDNA/CP connected in series between the clips of working and counter electrodes of a potentiostat and a reference electrode were immersed in aqueous solution containing TAM, the interaction of dsDNA with TAM produced a change in interfacial potential at the dsDNA/CP/solution interface. When linear sweep potential was applied to the dsDNA/CP and the corresponding I-E curve was recorded, interfacial potential offset applied potential partially, making the I-E curve displace along potential axis. Zero current potential where circuit current I was equal to zero in the I-E curve was measured to check the displacement of the I-E curve. Based on the displacement, the thermodynamic constants of the interaction between dsDNA and TAM were determined. The binding ratio of dsDNA with TAM was found to be 1:1 and the apparent binding constant was (6.85±0.20)×10(6) M(-1). As zero current potentiometry was independent of the changes in redox potential or current of both dsDNA and TAM themselves, the interaction was studied in their natural forms without damage. Moreover, TAM can be determined. The detection limit was 1.1×10(-7) M.

Exciton diffusion and charge transfer dynamics in nano phase-separated P3HT/PCBM blend films.

Exciton quenching dynamics has been systematically studied in pristine P3HT and nano phase separated P3HT/PCBM blend films under various excitation intensities by femtosecond fluorescence up-conversion technique. The behaviors of excitons in the films can be well described by a three-dimensional diffusion model. The small diffusion length and large charge transfer radius indicate that excitons reach the interface most likely by the delocalization of the excitons in P3HT fibrillar at a range of 4.8-9 nm so that the excitons can quickly delocalize in the P3HT domain to reach the interface (instead of by diffusion).

Magnetic-mesoporous Janus nanoparticles.

Novel multifunctional magnetic-mesoporous Janus particles with controlled aspect ratio were developed by a simple one-step synthesis approach. Due to their superior magnetic properties and well-defined pore structures, these particles will be important in drug delivery, molecule targeting, cellular imaging, and as building blocks for the assembly of complex nanostructures.

Electrochemiluminescence of palmatine being oxidized by electrogenerated hydroxyl radical and its analytical application.

A strong electrochemiluminescence (ECL) of palmatine in NaOH medium was observed at a vaseline-impregnated graphite anode. The ECL production could be described as follows: hydroxyl radical (OH(•)) was generated via the oxidation of hydroxyl group (OH(-)) in NaOH medium, and the formed OH(•) subsequently oxidized palmatine base converted from palmatine in NaOH medium to the excited state oxypalmatine (oxypalmatine*). As the oxypalmatine* went back to its ground state, a stronger chemiluminescence was produced. Based on the ECL of palmatine, an ECL method for the determination of palmatine was proposed. An ECL signal of palmatine in NaOH solution was obtained by applying direct current of 15 mA to the vaseline-impregnated graphite anode. The ECL intensity was rectilinear with palmatine concentration in the range of 8.0 × 10(-7) to 2.0 × 10(-5) mol l(-1) and the limit of detection (signal-to-noise = 3) was 3 × 10(-7) mol l(-1) . The proposed method was applied to the determination of palmatine in pharmaceutical preparations.

Surface-enhanced Raman scattering substrates of high-density and high-homogeneity hot spots by magneto-metal nanoprobe assembling.

Binary naoparticles composed of a superparamagnetic Fe(3)O(4) core and an Au nanoshell were prepared via a high-temperature hydrolysis reaction followed by seed-mediated growth. The nanoprobes render simultaneous dual functions of both fast magnetic response and local surface plasmon resonance. Using these nanoprobes, analyte molecules can be easily biologically captured, magnetically concentrated, and analyzed by surface-enhanced Raman scattering (SERS). Particularly, the complex particles were assembled under magnetic force direction into a SERS substrate. It was found to possess both a high enhancement factor (10(6)) and high homogeneity of "hot spot" distribution (fluctuation less than 20% for a 1 µm(2) area) with 4-aminothiophenol as the analyte.

Suspended optical fiber-to-waveguide mode size converter for silicon photonics.

In this paper, an efficient and novel optical fiber-to-waveguide mode size converter for Si Photonics devices with sub-micron waveguides is developed on the SOI platform. This optical converter is composed of a suspended SiO(2) waveguide and overlapped Si nano-tapers located in the center of suspended SiO(2) waveguide. Laterally connected SiO(2) beams provide structural support for the suspended SiO(2) waveguide. The optical input signal from the optical fiber is launched into the suspended SiO(2) waveguide, and then coupled into the Si nano-taper. The measured coupling loss using a lensed fiber with 5 microm spot diameter is 1.7 ~2.0 dB/facet for TE mode and 2.0 ~2.4 dB/facet for TM mode in the wavelength range of 1520 ~1600 nm. When a cleaved fiber with 9.2microm spot diameter is used, the coupling losses for both TE and TM modes are less than 4.0 dB/facet at 1550 nm. For the case of lensed fiber, the alignment tolerances for both TE and TM modes are about +/- 1.7 microm for 1 dB excess loss in both X and Y axes. The alignment tolerances for both modes of TE and TM are relaxed, exceeding +/- 2.5 microm for 1 dB excess loss in both X and Y axes when a cleaved fiber is used.

WDM multi-channel silicon photonic receiver with 320 Gbps data transmission capability.

A high performance monolithically integrated WDM receiver is fabricated on the SOI platform, with key components comprising a 1 x 32 Si-based AWG and an array of high speed waveguided Ge-on-Si photodetectors. The optical channel spacing is 200 GHz. This configuration was used to demonstrate 32-channel operation in the L-band, where it is particularly challenging for silicon photonics due to the low absorption coefficient of Ge at L-band wavelengths. Each channel is capable of operating at a data rate of at least 10 Gbps, resulting in an aggregate data rate of 320 Gbps. At a BER of 1 x 10(-11), the WDM receiver showed an optical input sensitivity between -16 dBm and -19 dBm.