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We present a device that can achieve controlled transport of colloidal microparticles using an array of micro-electrodes. By exciting the micro-electrodes in regular sequence with an AC voltage, a time-varying moving dielectrophoretic force-field is created. This force propels colloidal microparticles along the electrode array. Using this method, we demonstrate bidirectional transport of polystyrene micro-spheres. Electromagnetic simulation of the device is performed, and the dielectrophoretic force profile around the electrode array is mapped. We develop a Brownian dynamics model of the trajectory of a particle under the influence of the time-varying force-field. Numerical and experimental results showing controlled particle transport are presented. The numerical model is found to be in good agreement with experimental data. The developed numerical framework can be useful in designing and modeling lab-on-a-chip devices that employ external non-contact forces for micro-/nanoparticle manipulation.

A semi-analytical model is proposed to describe the force generated by a near-field optical trap. The model contains fitting parameters that can be adjusted to resemble a reference force-field. The model parameters for a plasmonic near-field trap consisting of a C-shaped engraving are determined using least squares regression. The reference values required for the regression analysis are calculated using the Maxwell stress tensor method. The speed and accuracy of the proposed model are compared with the conventional method. The model is found to be significantly faster with an acceptable level of accuracy.

Lead barium niobate (Pb1−xBaxNb2O6) is a very promising material for photorefractive applications in that it has a high ferroelectric-to-paraelectric transition temperature (300–500 °C depending on composition) and simultaneously can have large electro-optic coefficients, because of the nearly vertical morphotropic phase boundary (MPB) near 1−x=0.63. Pb1−xBaxNb2O6 crystals have been grown by the vertical Bridgman method for near-MPB compositions (0.5

Lead barium niobate crystals (Pb1−xBaxNb2O6) are attractive photorefractive materials for holographic data storage. The electro-optic coefficients r33 and r13 are determined using a Mach–Zehnder interferometer setup, and are measured to be 160±20 and 32±4 pm/V, respectively. The angular dependence of the photorefractive two-beam coupling gain is also investigated, and the products of the electro-optic coefficients and the electron-hole competition factor rζ are determined and compared with the electro-optic coefficients obtained using the interferometric method. It is found that the electron-hole competition factor is at least 0.7, indicating that the photorefractive process is mostly due to electrons. The effective trap densities at several wavelengths are also determined from the gain dispersion measurements, and are found to be 1.3–2.2×1016 cm−3.

A transient, two-dimensional drift-diffusion model is developed for optically addressed spatial light modulators made with quantum-well materials. The transport of free and well-confined carriers is considered along with nonlinear transport effects such as velocity saturation, field-dependent carrier escape from quantum wells, and resonant absorption. In addition to full numerical solutions to the transport equations, analytical and simplified numerical solutions are developed to describe basic screening behavior and to give estimates of speed and resolution performance. In particular, a self-consistent small signal model is developed to justify the surface-charge picture often used to describe device operation. This model is also used to simulate grating formation and decay. It is found that the maximum screening rate and peak grating amplitude are achieved using vertical drift lengths much longer than the device length. A detailed analysis of resolution performance is also given in which the effects of ...

A computationally efficient method for identifying the parameters of the Jiles-Atherton hysteresis model is presented. Adjoint analysis is used in conjecture with an accelerated gradient descent optimization algorithm. The proposed method is used to estimate the Jiles-Atherton model parameters of two different materials. The obtained results are found to be in good agreement with the reported values. By comparing with existing methods of model parameter estimation, the proposed method is found to be computationally efficient and fast converging.

We have conducted measurements of the linear electro‐optic coefficient (r41) and electrogyratory coefficient (η41) in Bi12TiO20 at 633 nm. A precise knowledge of these coefficients is important for evaluating the holographic recording properties of this photorefractive material. We have employed both transverse and longitudinal electric field geometries. For each geometry, we present the results of dc as well as ac techniques. Based on these results we find r41=5.75±0.10 pm/V and ‖η41‖≤0.30±0.05 pm/V. We critically examine our measurements and discuss their relative accuracy. Our findings are compared to those previously reported by other investigators.

Rear surface spallation of single-crystal silicon under 5‐ns laser pulse ablation at intensities of 0.6–60GW∕cm2 is studied through postablation examination of the ablated samples. The spallation threshold energy and the spallation depth’s dependences on the energy and target thickness are measured. From the linear relation between the spallation threshold energy and the target thickness, an estimation of the material spall strength around 1.4GPa is obtained, in reasonable agreement with the spall strength estimation of 0.8–1.2GPa at a strain rate of 107s−1 using Grady’s model for brittle materials. The experiment reveals the internal fracturing process over an extended zone in silicon, which is controlled by the competition between the shock pressure load and the laser ablation rate. The qualities of the laser microstructuring and micromachining results are greatly improved by using an acoustic impedance matching approach.