Showing 3 results for Stability.
H. Pakarzadeh, A. Zakery,
Volume 4, Issue 1 (1-2010)
Abstract
In this paper, by including Raman scattering in the coupled-mode equations, the scalar modulation instability in photonic crystal fibers is investigated. The evolution of the pump, Stokes and anti-Stokes waves along the fiber as well as the conversion efficiency for two cases, with and without Raman effect, are studied. The effect of anti-Stokes seed and the pump depletion on the evolution of Stokes wave is also considered. Moreover, the parametric gain when it is affected by Raman gain is dealt with. The results show that it is important to take into account Raman scattering, especially for wide-bandwidth parametric amplifiers which results in an asymmetric spectrum and more amplification of the Stokes wave.
Dr. Mohsen Hatami, Ms. Elham Yousefi,
Volume 7, Issue 2 (8-2013)
Abstract
In this study, a new numerical method is introduced to obtain the exact shape of output pulse in the chalcogenide fiber Bragg grating (FBG). A Gaussian pulse shape with 173 ps width is used as an input pulse for lunching to a 6.6 mm nonlinear FBG. Because of bistable and hysteresis nature of nonlinear FBG the time sequence of each portion of pulse is affected the shape of output pulse. So we divide the pulse to leading and trailing portion in time. By using bistability curve and Fourier transformation, the exact shape of output pulse is simulated. In comparison of non-unique solution for output pulse in the previous papers, the results of this study have an optional merit.
Asieh Nazari Mofrad, S.m. Bagher Ghorashi, Farhad Jahantigh,
Volume 15, Issue 1 (1-2021)
Abstract
One of the main challenges for perovskite solar cell (PSCs) structures is their high sensitivity to humidity and ambient temperature, which significantly lowers the lifespan of these devices. Low stability of this devices is considered one of the principal limitations to make them commercialized. To increase the stability of the solar cell is to encapsulate the solar cell. The encapsulation is to cover the device with a non-reactive material, which prevents the penetration of ambient moisture and increases the thermal stability of the cell. If the uncoated device is exposed to continuous incident light for several hours, its structure is damaged while encapsulated device has a longer duration time. Several methods have been proposed for encapsulating a perovskite solar cell. The principal strategy of these methods involves deposition of a thin layer of polycarbonate polymer on the perovskite solar cell structure, resulting in layers of the desired structure. After fabrication and encapsulation process, the order of the various layers are FTO / bl-TiO2 / mp-TiO2 / Perovskite (CH3NH3PbI3) / Spiro-OMETAD / Au / Polycarbonate Polymer. To increase the effective stability, the glass coating is placed on the polycarbonate polymer. After acquiring sufficient adhesion between the glass coating and the polymer layer on the structure of PSCs, UV epoxy is used to seal the whole structure. Having performed the encapsulation, the samples were exposed every day to 85% constant humidity and 85°C temperature for 10 hours and it was observed that the cell efficiency, under the mentioned conditions and after successive measurements, maintained to a high extent.
