International Journal of

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By introducing a thin ZnO layer as an optical spacer, we have demonstrated that inserting this layer between an active layer and a reflective electrode results in a re-distribution of the optical electric field inside bulk heterojunction solar cells. A theoretical analysis by optical modeling showed that the thin ZnO layer could shift the position of the maximum of the electric field into the absorbing layer. Theoretical calculations were compared with experimental results for devices with and without an optical spacer. By using a ZnO optical spacer layer, a significant increase was observed in the short circuit current density of J-V curves. This increase might be due to harvesting more lights and also hole-blocking by the ZnO layer. Both electrical and optical characteristics of the device provided improved results in the power conversion efficiency of the bulk heterojunction solar cell up to 3.49%.

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Based on transformation optics‎, ‎we propose an illusion device that can make‎ ‎objects look much smaller and different than they actually are‎. ‎In particular‎, ‎the device has a capability to hide a large object (like an elephant) into a‎ ‎small one (like a matchbox)‎. ‎Compared to previous proposals for illusion‎ ‎devices‎, ‎there is no requirement for negative refractive index or for speed of‎ ‎light going to infinity as in Euclidean invisible cloaks‎. ‎We demonstrate the‎ ‎functionality of the device by full wave simulations‎.

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Simultaneous laser induced- breakdown spectroscopy (LIBS) and acoustic response techniques as well as Laser induced fluorescence (LIF) are applied to investigate the abnormal lymph tissues due to Hodgkin disease. The spectral shift in the emissive fluorescence of the cancerous tissues has been observed respect to the normal ones. Regarding LIBS, the concentrations of Ca and Na trace elements have been identified to be higher in the cancerous samples. In addition, the acoustic response of cancerous tissues has been elevated against healthy ones. The distinct differences in the spectra are taken into account for early and the rapid identification and diagnosis.

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Considering a temperature dependent two-level quantum system, we have numerically solved the Landau-Zener transition problem. The method includes the incorporation of temperature effect as a thermal noise added Schrödinger equation for the construction of the Hamiltonian. Here, the obtained results which describe the changes in the system including the quantum states and the transition probabilities are investigated and discussed. The results successfully describe the behavior of the transition probabilities by sweeping the temperature.

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The nonlinear effects of the second harmonic generation have been investigated for the propagation of light along the axis of fibers of wagon wheel cross sectional shape. Nodal finite element formulation is utilized to obtain discretized Helmholtz equations under appropriate boundary conditions. The hierarchical p-version nodal elements are used for meshing the cross section of wagon wheel fiber. The fiber material has been chosen to be LiTaO₃ to provide proper second harmonic generation. Propagation of generated second harmonics for two incident field amplitudes are studied in this work.

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In this paper, we have proposed and demonstrated a new method of atomic population transfer. The transition dynamic of a two-level system is studied in a full quantum description of the Jaynes-Cummings model. Solving the time-dependent Schrödinger equation, we have investigated the transition probabilities numerically and analytically by using a sudden boost of the laser frequency. The results show that complete population transfer can be achieved by adjusting the time of the frequency boost.

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ta charset="UTF-8" >Optogenetics is an advanced optical tool in neuroscience research. However, light stimulation in optogenetic experiments may also affect neural function by generating heat. In this paper, the effect of increasing the temperature of the brain tissue was studied during light stimulation. The Hodgkin-Huxley model and the hippocampal pyramidal cell model have been used to investigate the effect of temperature on spike neurons. The modeling results show that irradiation of brain tissue by pulsed laser with a frequency of 40 Hz, the duty cycle of 90% and wavelength of 593 nm at a distance of 10 μm from the tip of the fiber, for 60 seconds with a power of 1 and 40 mW leads to the temperature change from 37 °C to 39 °C. The obtained results show that the laser intensity decreases to zero at a distance of 1 mm from the tip of a fiber, which is absorbed by the tissue and causes a temperature rise of 2 °C that can increase the spike rate of neurons by 16.6%.