Zhanchen Cui

Preparation and characterization of ZnS–polymer nanocomposite films with high refractive index

Novel ZnS–poly(urethane-methacrylate macromer) (PUMM) nanocomposite films with high refractive index were prepared by incorporating thiophenol (PhSH)–4-thiomethyl styrene (TMSt)-capped ZnS nanoparticles into a urethane-methacrylate macromer (UMM), followed by spin-coating and ultraviolet radiation initiated free radical polymerization. PhSH–TMSt-capped colloidal ZnS solution was synthesized by reacting zinc acetate with H2S in N,N-dimethylformamide. UMM macromer was synthesized by reacting 2-hydroxyethyl methacrylate (HEMA) with isocyanate group terminated polythiourethane oligomer which was obtained from polyaddition of 2,2′-dimercaptoethyl sulfide (MES) with 2,4-tolylene diisocyanate (TDI). Thiol-capped ZnS nanoparticles were characterized and found to be 2.0–5.0 nm in diameter with a cubic phase structure. The chemical composition of these ZnS nanoparticles was determined to be Zn2+ ∶ S2− ∶ RS− = 1 ∶ 0.6 ∶ 0.6 using chemical analysis methods. The weight fraction of ZnS nanoparticles in the films was measured by TGA, and it accords well with that of theoretical calculation. FTIR and DSC studies show that ZnS nanoparticles were successfully immobilized into the polymer matrix and the resulting nanocomposite films have a good thermal stability. TEM images indicate that the ZnS nanoparticles were uniformly dispersed in the polymer matrix and the particles remained their original size (2–5 nm) before incorporation into the polymer matrix. The XPS depth profiling technique demonstrates that the ZnS nanoparticles were also dispersed homogeneously in the depth scales of the polymer matrix. The nanocomposite films show high optical transparency in the visible region (T > 95% at 550 nm) and high refractive index in the range of 1.645–1.796 at 632.8 nm as the content of thiol-capped ZnS nanoparticles linearly increased from 0 to 86 wt%.

High refractive index thin films of ZnS/polythiourethane nanocomposites

High refractive index optical thin films of nano-ZnS/polythiourethane (PTU) composites have been prepared via immobilization of thiophenol (PhSH)/mercaptoethanol (ME)-capped ZnS nanoparticles into a PTU matrix. PhSH/ME-capped ZnS particles with a diameter of 2–6 nm were synthesized by reacting zinc acetate with H2S in N,N-dimethylformamide. The nanocomposite films with high refractive index were prepared by adding an isocyanate group terminated PTU oligomer, which was synthesized by polyaddition of 2,2′-dimercaptoethylsulfide (MES) and isophorone diisocyanate (IPDI), to a DMF solution containing colloidal ZnS particles, and followed by spin-coating and multi-step heat curing. FTIR studies show that the ZnS nanoparticles were successfully immobilized into the polymer matrix. TGA results indicates that the nanocomposite films have a good thermal stability and the weight fraction of ZnS particles in the films is well in accordance with that of theoretical calculations. TEM studies suggest that the ZnS nanoparticles with a diameter of 2–6 nm were well dispersed in the PTU matrix and maintained their original size before immobilization. The refractive index of the transparent ZnS/PTU nanocomposite films was in the range from 1.574 to 1.848 at 632.8 nm, which linearly increased with the content of PhSH/ME-capped ZnS from 0 to 97 wt%.

The synthesis and characterizations of monodisperse cross-linked polymer microspheres with carboxyl on the surface

Monodisperse cross-linked polymer microspheres with carboxyl groups on their surface were prepared by means of emulsifier-free emulsion copolymerization. The characterizations by X-ray photoelectron spectroscopy and conductometric titration indicate that most carboxyl groups are located on the surface of microspheres. Their swelling degree or cross-linking degree has been investigated by an in situ swelling method. Moreover, these microspheres can be easily and quickly self-organized into two- or three-dimensional ordered multilayer films or latex crystals.

A novel method for the layer-by-layer assembly of metal nanoparticles transported by polymer microspheres

A novel method for the assembly of metal nanoparticles is reported, in which polymer microspheres have been employed as both stabilizers and transport vehicles. We prepared sulfonated polystyrene microspheres and then introduced silver ions into the microspheres by ion exchange. Dispersal of the polymer microspheres in DMF led to the silver ions in them being reduced by the solvent; the resulting Ag nanoparticles were stabilized by the polymer network. In aqueous solution, the polymer microspheres are negatively charged and, by using layer-by-layer method, the prepared Ag nanoparticles can be self-assembled into films using the microspheres as transport vehicles.

UV Curable Electro-Optic Polymer Switch Based on Direct Photodefinition Technique

In this paper, a new type of single-mode embedded dye-doped electro-optic (EO) polymeric waveguide switch based on cross-linkable negative photoresist was successfully designed and fabricated using direct photodefinition technique. The optical properties of the UV cross-linkable poled polymer were characterized. By optimizing the poling temperature and the dopant levels of Disperse Red 1, the DR1/SU-8 material showed excellent photostability and exhibited an EO coefficient, γ33, of 25 pm/V. The characteristic parameters of both the waveguide and the electrode were carefully designed and simulated by MATLAB program. The Mach-Zehnder interferometer switch on-off time obtained was about 6 μs. The new fabrication technique is a simple, rapid, and controllable process. The easy-to-fabricate waveguide structure is suitable for planar active lightwave circuit applications. The dye-doped polymer photosensitive waveguide devices will be very useful in realizing EO modulators and switches.

Parameter optimization and structural design of polymer arrayed waveguide grating multiplexer

Abstract First some important parameters are optimized for the structural design of a polymer arrayed waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm. These parameters include the thickness and width of the guide core, mode effective refractive indices and group refractive index, diffraction order, pitch of adjacent waveguides, length difference of adjacent arrayed waveguides, focal length of slab waveguides, free spectral range (FSR), the number of input/output (I/O) channels, and that of arrayed waveguides. Then the bent angles, radii and lengths of all the input/output channels and arrayed waveguides are determined. Finally, a schematic waveguide layout of this device is presented, which contains 2 slabs, 11 input channels, 11 output channels, and 91 arrayed waveguides.

Electro-Optic Modulator Based on Novel Organic-Inorganic Hybrid Nonlinear Optical Materials

A Mach-Zehnder type electro-optic (EO) modulator based on novel organic-inorganic hybrid nonlinear optical materials attached with Disperse Red 19 has been successfully designed and fabricated. The new material system presents a smartly controlled process to overcome the EO effect stability tradeoff of conventional EO polymers and obtains poling efficiency and thermal stability. The characteristic parameters of both the embedded waveguide and the coplanar waveguide traveling-wave electrode are carefully designed and simulated by MATLAB program. The optimized structural properties and fabrication procedures are demonstrated. The electrical-optical overlap factor of fundamental mode is obtained as 85.62%. The device exhibits an EO coefficient of 12.8 pm/V at 1550 nm and stable operation, which shows potential for planar active light-wave circuit applications.

Reconfigurable optical interleaver modules with tunable wavelength transfer matrix function using polymer photonics lightwave circuits

A transparent reconfigurable optical interleaver module composed of cascaded AWGs-based wavelength-channel-selector/interleaver monolithically integrated with multimode interference (MMI) variable optical attenuators (VOAs) and Mach-Zehnder interferometer (MZI) switch arrays was designed and fabricated using polymer photonic lightwave circuits. Highly fluorinated photopolymer and grafting modified organic-inorganic hybrid material were synthesized as the waveguide core and caldding, respectively. Thermo-optic (TO) tunable wavelength transfer matrix (WTM) function of the module can be achieved for optical routing network. The one-chip transmission loss is ~ 6 dB and crosstalk is less than ~25 dB for transverse-magnetic (TM) mode. The crosstalk and extinction ratio of the MMI VOAs were measured as -15.2 dB and 17.5 dB with driving current 8 mA, respectively. The modulation depth of the TO switches is obtained as ~18.2 dB with 2.2 V bias. Proposed novel interleaver module could be well suited for DWDM optical communication systems.

Monolithic multi-functional integration of ROADM modules based on polymer photonic lightwave circuit

A transparent reconfigurable optical add-drop multiplexer (ROADM) module composed of AWG-based wavelength-channel-selectors monolithically integrated with Mach-Zehnder interferometer (MZI) thermo-optic (TO) waveguide switch arrays and arrayed waveguide true-time-delay (TTD) lines is designed and fabricated using polymer photonic lightwave circuit technology. Negative-type fluorinated photoresist and grafting modified organic-inorganic hybrid materials were synthesized as the waveguide core and cladding, respectively. The one-chip transmission loss is ~6 dB and the crosstalk is less than ~30 dB for the transverse-magnetic (TM) mode. The actual maximum modulation depths of different thermo-optic switches are similar, ~15.5 dB with 1.9 V bias. The maximum power consumption of a single switch is less than 10 mW. The delay time basic increments are measured from 140 ps to 20 ps. Proposed novel ROADM is flexible and scalable for the dense wavelength division multiplexing network.

Organic thin-film transistors with novel high-k polymers as dielectric layers

This study describes a general approach to design and synthesize a series of novel high-k polymers containing p-conjugated structures with cyano groups for use as a dielectric layer in organic thin-film transistors (OTFTs). The polymer dielectric films have been evaluated based on surface morphology, dielectric constant, leakage current density and compatibility with organic semiconductors, which can be readily fabricated via solution processes in an ambient atmosphere. The characterization confirms that the p-conjugated structures with cyano groups can provide a high dielectric constant (high-k) and a low electrostatic loss. With these polymer dielectric layers, para-sexiphenyl (p-6P)/vanadyl-phthalocyanine (VOPc) OTFTs exhibit excellent performances with a threshold voltage of -3.22 V, a charge carrier mobility of 0.49 cm(2) V-1 s(-1), and an on/off current ratio >10(6).