JEOS:RP - Journal of the European Optical Society Rapid publications
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Adhesion of functional layer on polymeric substrates for optoelectronic applications
Get PDFThe use of plastic film substrates for organic electronic devices promises to enable new applications, such as flexible displays. Plastic substrates have several distinct advantages, such as ruggedness, robustness, ultra lightness, conformability and impact resistance over glass substrates, which are primarily used in flat panel displays (FPDs) today. However, high transparency, proper surface roughness, low gas permeability and high transparent electrode conductivity of the plastic substrate are required for commercial applications. Polyesters, both amorphous and semicrystalline, are a promising class of commercial polymer for optoelectronic applications. Surface modification of polyester films was performed via chemical solution determining hydrolysis or oxidation. Hydrolysis was carried out by means of sodium hydroxide solution and oxidation by using standard clean 1 (SC-1) of RCA procedure [1]. For this work we have used commercial polymer films of 100µm in thickness: AryLite™ [2], supplied by Ferrania Imaging Technologies S.p.A. and characterised by very high glass transition temperature, Mylar™ (Polyethylene Terephthalate PET) and Teonex™ (Polyethylene Naphthalate PEN) both supplied by Dupont. More over, a bioriented and semicrystalline PET have been used.
The aim of this study is modifying the polymer surface to improve the adhesion between organic-inorganic layer. It was found that the NaOH and SC-1 treatment cause a decrease of contact angles. In the present study we have deposited a thin films of amorphous hydrogenated silicon (a-Si:H) and its oxide (SiO2) on a new high temperature polymer substrate, AryLiteâ„¢, by plasma enhanced chemical vapour deposition (PECVD) [3], with a radio frequency plasma system
A hybrid time-domain model for pulsed terahertz dipole antennas
Get PDFIn this paper we study the effect of the length of dipole antennas on the spectrum of the radiated THz signal in pulse-excited opto-electronic terahertz systems. In particular, we investigate the origin of the commonly observed sharp dips that occur in the spectra of photoconductive dipole antennas, and explain them on the basis of reflections of the excitation current pulse that take place at the ends of the antenna. We develop a hybrid time-domain model for the system and show that the predictions of our model are in good agreement with experimental results
Curved plasma channels: Kerr lens and Airy prism
Get PDFWe analytically calculate the transverse energy fluxes induced in high-power Airy beams by the Kerr self-focusing and the Airy profile itself, respectively. In experimental condition representative of laser filamentation experiments of high-power, ultrashort laser pulses in air and condensed media, the Kerr lens induces transverse energy fluxes much larger than the Airy "prism" at the main peak. As a consequence, the curved plasma channels in Airy beams are not only a plasma spark on a curved focus, but indeed self-guided filaments, and their curved trajectory appears as a perturbation due to the linear Airy propagation regime
Femtosecond optical frequency comb-based tandem interferometer
Get PDFThe principle of a unique interferometer, called a femtosecond optical frequency comb-based (FOFC-based) tandem interferometer, is proposed and demonstrated for the first time. By taking advantage of both the temporal coherence characteristic of an FOFC light source and the transmission characteristics of acquired length information based on a tandem interferometer, the present technique is expected to be useful for high-precision measurement of long distances for not only science purposes but also industry requirements
Object wave reconstruction by speckle illumination and phase retrieval
Get PDFAn innovative setup for the speckle-based phase retrieval method is proposed. In the conventional setup, a plane wave illuminates the test object and the transmitted wavefront is incident on a diffuser aperture generating a speckle field. The sampled speckle intensities at axially displaced planes are input into a phase retrieval algorithm based on a wave propagation equation. In the new setup, the arrangement of the diffuser and the object is reversed. A plane wave incident on the diffuser generates a speckle field which, in turn, is used to illuminate the object. The transmitted wavefront is then directed to the camera sensor. The advantage of the proposed setup is the increased resolution since the limiting aperture is the full area of the sensor
Self-phase modulation effects and pulse propagation in gain-guided fibers
Get PDFWe present a theoretical analysis of pulse propagation and self-focusing in a gain-guided (GG) fiber amplifier. A weak pulse is launched in the GG fiber when the input pulse reaches a critical power the pulse begins to collapse in the transverse direction. By using different input powers the transmission characteristics are changed. We add coupling to a single-mode fiber at the output end and study pulse dispersion and energy
Spectrally narrow polarisation conversion in a slow-light photonic crystal waveguide
Get PDFA narrow-band (3dB bandpass < 2 nm) transmission notch based on polarisation conversion within a SOI photonic crystal waveguide is demonstrated. Signal contrast between quasi- TE and TM eigenstates exceeding 40 dB is achieved. Further, multiple resonant wavelength coupling between the two eigenstates is also observed
Investigations on the Bragg grating recording in all-silica, standard and microstructured optical fibers using 248 nm 5 ps, laser radiation
Get PDFThe fabrication of Bragg reflectors in hydrogenated, all-silica, fluorine cladding depressed and microstructured optical fibers using 248 nm, 5 ps laser radiation, is investigated here. Comparative Bragg grating recordings are performed in both optical fibers, for investigating effects related to the scattering induced by the capillary micro-structure, to the photosensitivity and index engineering yield. Further, finite difference time domain method is employed for simulating the scattering from the above capillary structure and the nominal intensity reaching the fiber core for side-illumination. The maximum modulated refractive index changes inscribed in the standard, step-index fiber were of the order of 8.3x10-5, while the maximum refractive index changes inscribed in one of the microstructured optical fibers was 32% lower and 5.7x10-5, for nominal pulse intensities of 20 GW/cm2 and modest accumulated energy densities
Determination of 3D-region of interest using digital in-line holography with astigmatic Gaussian beams
Get PDFAn experimental method to visualize a 3D-region of interest (ROI) by means of an astigmatic Gaussian beam is proposed. This method allows to reduce the amount of image planes to be reconstructed thus saving computational time. ROI determination is performed without any computational step: particles that are located in the ROI can be distinguished from the others according to the hyperbolic shape of their diffraction pattern. Theoretical location of the ROI is determined by using the ABCD approach proposed in a previous paper [Appl. Opt. 47, 4147]. Experimental results are presented
A study of optical solitons with Kerr and power law nonlinearities by He's variational principle
Get PDFThis paper studies optical solitons, in presence of perturbation terms, by the aid of He's variational principle. The inter-modal dispersion, self-steepening, nonlinear dispersion and Raman scattering are all treated as perturbation terms. Both Kerr law as well as power law nonlinearities are considered in this paper