Surface-modified polyacrylonitrile nanofibers as supports

Polyacrylonitrile nanofibers (PAN-nfs) are one of the most studied nanofibres because of their excellent characteristics, such as good mechanical strength, chemical resistance, and good thermal stability. Due to the easy dissolution in polar organic solvents, PAN-nfs are mostly produced via electrospinning technique. The electrospun PAN-nfs surfaces are relatively in-active and hydrophobic, and, therefore, hinder some potential applications; however, chemical surface modification reactions, such as amination, reduction, hydrolysis, and amidoximation, have been carried out on them. These reactions bring about functional groups, such as amine, hydroxyl, carboxylic, imine etc, to the surface PAN-nfs and invariably make their surfaces active and hydrophilic. The surface-modified PAN-nfs have been used as supports for organic compounds, enzymes, and antibodies in biological studies. They have also been used for immobilization of various organic ligands for adsorption of metal ions in water. Furthermore, because of their ability to complex metal ions, several surface-modified PAN-nfs have also been used as supports for transition metal catalysts in Fenton’s chemistry.IS

Simulations of fast switching between longitudinal modes of the novel semiconductor tunable laser with filtered optical feedback

A system of delay differential rate equations is introduced as a tool to investigate switching dynamics induced by on-chip filtered feedback in Photonic Integrated Circuits. We show different switching mechanisms between lasing modes that can be induced by modulation of the frequencies of the feedback filter. Finally a novel integrated tunable laser is presented which operates according to such control scheme

Fast integrated discretely tunable laser using filtered feedback for packet switching and access network applications

In this paper we report the design, fabrication, simulation and characterization of a novel discretely tunable laser based on filtered feedback. This Integrated Filtered-Feedback Tunable Laser (IFF-TL) device combines a simple and robust switching algorithm with good wavelength stability. It consists of a Fabry-Perot laser with deeply-etched broadband DBR mirrors. Single mode operation is achieved by using feedback from an integrated filter. This filter contains an AWG wavelength router and an SOA gate array. A rate equation model predicts that a properly designed device can switch within 1 ns, while characterization measurements show a value of only 4 ns. The fast switching and reduced control complexity makes the device very promising for various advanced applications in optical telecommunication networks

Characterization of polycrystalline Cu(In,Ga)Te2 thin films prepared by pulsed laser deposition

Thin films of the chalcopyrite compound CuGaXIn1-XTe2 (0=<X=<1) have been prepared by pulsed laser deposition (PLD) of prereacted material onto glass substrates. The structural and optical properties of these films have been investigated using the techniques of X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), Rutherford back scattering (RBS), transmittance (T), reflectance (R). Electrical characterization was performed using Hall and resistivity measurements, using the Van der Pauw technique at 300 K. The composition of the laser-deposited films was found to closely match that of the target materials and the XRD showed them to be single phase with the chalcopyrite structure and a preferred orientation along the (112) plane. The spectral dependence of the refractive index n and absorption coefficient alpha of the Cu(In,Ga)Te2 thin films were determined using rigorous expressions for transmission and reflection in an air/film/substrate/air multilayer system. The CuGaXIn1-XTe2 films had optical absorption coefficients of order 104 cm-1 and the energy gaps observed in these films increased from 0.96 to 1.32 eV with increasing Ga content