Domain studies of CoCr with perpendicular anisotropy

R.F. Magnetron sputtered CoCr films (79/21 at%) with various thicknesses are magnetically characterized. The domain structure is observed by digitally enhanced Kerr microscopy and depends on the Hc/Hk values of the samples. For low and high coercivity films a comparison is made between the measured VSM hysteresis, domain period and a theoretical domain model. The domain shape is a function of the magnetic history of the sample and the bending created by the deposition process

Characterization of optical third-order non-linearities by prism coupling and pulse shape analysis on a ps timescale

Materials with an intensity dependent index of refraction and absorption coefficient¿third-order optical non-linear (ONL) effects¿offer the possibility of all-optical signal processing. Prism coupling is a well-known tool to investigate the intensity dependent refractive index, however, such experiments are often obscured by thermal effects. To avoid these we have studied the influence of the ONL effects on the shape of 70 ps pulses in non-linear prism coupling. The full width at half maximum (FWHM) of the in and out coupled pulses is compared simultaneously with the FWHM of the pulses of a reference beam. By measuring at various angles of incidence around that for optimal coupling it is possible to measure the sign and value of the change in both the refractive index and absorption coefficient. As a function of the coupling angle, the first leads to an asymmetric line shape for the ratio of the two FWHMs mentioned above, whereas the second leads to a symmetric one. From a comparison of simulations with experimental data, the values of the non-linear constants can be derived

Optical response of highly granular YBaCuO films prepared by non-vacuum aerosol deposition

Highly granular YBaCuO films on SrTiO3 substrates with Tc,o~90K and Jc > 104 A/cm2 were prepared by non-vacuum aerosol deposition. The optical response for these films was investigated on a 10 × 10 μm2 microbridge. Besides a bolometric response around the transition temperature, a sharp response peak was observed at low temperature and high bias current using a He-Ne laser (0.63 μm wavelength) illumination. This response was caused by a junction behaviour due to the presence of many boundary-type weak links in our microbridge

Simple technique for two-photon absorption measurements in polymeric waveguide channels

A simple technique for two-photon absorption measurements by pulse shape deformation in channel optical waveguides is described. Measurements on a ps time scale are performed. Results are in good agreement with literature value

Design and realisation of mono-modal SiOxNy-based polymer waveguides for active functions

A method is described for optimising nonlinear mono-modal channel waveguides such that the guided power influences the propagation constant optimally. These waveguides have been used for a nonlinear MZI and measuring TPA. Experimental results are describe

Birefringence compensation in double-core optical waveguides

A new concept for birefringence compensation in planar optical waveguides applying a double-core structure is introduced. It is demonstrated on waveguides fabricated in silicon oxynitride technology for applications in optical telecommunicatio

Time domain beam propagation method for the simulation of temporal solitons in periodic media

A time domain beam propagation method for the simulation of optical pulses propagating through Kerr-nonlinear structures is presented. The method is verified by simulation of the known solitary wave solutions in nonlinear periodic medi

Granular YBaCuO films prepared by metalorganic chemical aerosol deposition technology

Fine-grain thin superconducting films can be prepared by metalorganic Chemical Aerosol Deposition Technology (CADT). In this paper, we present the preparation and properties of YBa2Cu3O7-x films on the different substrates, Si and SrTiO3 (100). It is shown that the zero-resistance temperature (Tc,0) of the films on SrTiO3 substrates is about 90 K, and the critical current density (Jc) at 77 K is above 104 A/cm2. In addition, these films exhibit significant grain-boundary weak link behaviour, which is very promising for applications in electronic devices

Dynamically enhanced supercurrents in granular superconducting Y-Ba-Cu-O thin films

Thin superconducting films of Y-Ba-Cu-O withT c0≊89 K have been prepared by the aerosol deposition method. The voltage current characteristic of microbridges (typically 10×10µm2) made from the finely granular films, which behave like a network of boundary Josephson junctions, is highly nonlinear and shows besides thermal effects evidence for dynamic enhancement of the supercurrent. Our experimental data are in qualitative agreement with a theory developed for conventional superconductors by Aslamazov and Larkin and also by Tinkham. A value for the electron phonon scattering time has been derived: τ E ≊15 ps

Evaluation of polymer based third order nonlinear integrated optics devices

Nonlinear polymers are promising materials for high speed active integrated optics devices. In this paper we evaluate the perspectives polymer based nonlinear optical devices can offer. Special attention is directed to the materials aspects. In our experimental work we applied mainly Akzo Nobel DANS side-chain polymer that exhibits large second and third order coefficients. This material has been characterized by third harmonic generation, z-scan and pump-probe measurements. In addition, various waveguiding structures have been used to measure the nonlinear absorption (two photon absorption) on a ps time-scale. Finally an integrated optics Mach-Zehnder interferometer has been realized and evaluated. It is shown that the DANS side-chain polymer has many of the desired properties: the material is easily processable in high-quality optical waveguiding structures, has low linear absorption and its nonlinearity has a pure electronic origin. More materials research has to be done to arrive at materials with higher nonlinear coefficients to allow switching at moderate light intensity (< 1 W peak power) and also with lower nonlinear absorption coefficients