Analysis of optical re-modulation by multistage modeling of RSOA

The time-resolved multistage reservoir model well-known for semiconductor optical amplifier (SOA) is extended to analyze the behavior of a bulk homogeneous InP-InGaAsP buried heterostructure reflective semiconductor optical amplifier (RSOA). Parameters for simulation have been extracted from the experimental RSOA characteristics. We have employed the model to explain the steady-state and re-modulation dynamics in the RSOA. Electrical modulation bandwidth and intermodulation distortion in the RSOA have been derived from the model and close agreement is obtained with the reported data. It is found out that the ripples in the upstream output from the RSOA for incomplete modulation erase of downstream modulated data follow Gaussian distribution, which simplifies the calculation of upstream SNR and bit error rate. It is explained in detail that amplitude ripples in the upstream data can be reduced by judicious choice of optical and electrical parameters of the RSOA. In particular, for an average low downstream power level (<−20 dBm) a good downstream modulation erase factor about 89% and 23 dB extinction ratio in the upstream modulated signal can be achieved.     

Effect of annealing on structural and optical properties of diamond-like nanocomposite thin films

The annealing effect on structural and optical properties of the Diamond-like Nanocomposite (DLN) thin film deposited on glass substrate by Plasma Assisted Chemical Vapor Deposition (PACVD) method has been investigated. The films were annealed at temperature ranging from 300 to 600 °C, with 100 °C interval for 9 minutes by rapid thermal process (RTP) under vacuum. The structural changes of the annealed films have been studied using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscope (SEM), and optical parameters have been determined using transmittance and reflectance spectra in UV-UIS-NIR range. The result shows that the refractive index increases gradually from 1.79 to 2.84 with annealing temperature due to out-diffusion of H by breaking Si–H and C–H bond leads to Si–C bond, i.e. more cross linking structure. In higher temperature range, graphitization also enhanced the refractive index. However, the optical band gap at up to 400 °C initially increases from 3.05 to 3.20 eV and then decreases due to graphitization. The film has a great potential to be used as anti-reflection coating (ARC) on silicon-based solar cell.     

Diluted magnetic ferroelectric effect in BaTi0.9Hf0.05Co0.05O3 ceramic

We report that magnetism, especially ferromagnetism, can be induced in a nonmagnetic ferroelectric oxide such as barium titanate (BaTiO₃) with choosing of suitable dopants. High-density polycrystalline sample of BaTi_0.9Hf_0.05Co_0.05O₃ was prepared using solid-state sintering route, and the effect of Co and Hf substitution on structural, magnetic and ferroelectric properties of BaTiO₃ was studied. The magnetic order obtained in the above sample is of intrinsic in nature. Ferromagnetic behavior shown in the BaTi_0.9Hf_0.05Co_0.05O₃ ceramic may be attributed to the effective exchange interactions between oxygen vacancies and Co ions. BaTi_0.9Hf_0.05Co_0.05O₃ ceramic has also shown ferroelectric (lossy type) behavior.     

Photovoltaic structures using AgSb(S x Se1−x )2 thin films as absorber

Photovoltaic structures were prepared using AgSb(S _x Se_1?x )₂ as absorber and CdS as window layer at various conditions via a hybrid technique of chemical bath deposition and thermal evaporation followed by heat treatments. Silver antimony sulfo selenide thin films [AgSb(S _x Se_1?x )₂] were prepared by heating multilayers of sequentially deposited Sb₂S₃/Ag dipped in Na₂SeSO₃ solution, glass/Sb₂S₃/Ag/Se. For this, Sb₂S₃ thin films were deposited from a chemical bath containing SbCl₃ and Na₂S₂O₃. Then, Ag thin films were thermally evaporated on glass/Sb₂S₃, followed by selenization by dipping in an acidic solution of Na₂SeSO₃. The duration of dipping was varied as 3, 4 and 5 h. Two different heat treatments, one at 350 °C for 20 min in vacuum followed by a post-heat treatment at 325 °C for 2 h in Ar, and the other at 350 °C for 1 h in Ar, were applied to the multilayers of different configurations. X-ray diffraction results showed the formation of AgSb(S _x Se_1?x )₂ thin films as the primary phase and AgSb(S,Se)₂ and Sb₂S₃ as secondary phases. Morphology and elemental detection were done by scanning electron microscopy and energy dispersive X-ray analysis. X-ray photoelectron spectroscopic studies showed the depthwise composition of the films. Optical properties were determined by UV–vis–IR transmittance and reflection spectral analysis. AgSb(S _x Se_1?x )₂ formed at different conditions was incorporated in PV structures glass/FTO/CdS/AgSb(S _x Se_1?x )₂/C/Ag. Chemically deposited post-annealed CdS thin films of various thicknesses were used as window layer. J–V characteristics of the cells were measured under dark and AM1.5 illumination. Analysis of the J–V characteristics resulted in the best solar cell parameters of V _oc = 520 mV, J _sc = 9.70 mA cm^?2, FF = 0.50 and η = 2.7 %.     

Biocompatible Carbon Dot Decorated α-FeOOH Nanohybrid for an Effective Fluorometric Sensing of Cr (VI) in Wastewater and Living Cells

Journal of Fluorescence - This article reports the fluorometric detection of toxic hexavalent chromium Cr (VI)) in wastewater and Cr (VI) contaminated living cells using in-situ grown carbon...     

Antitumour effect of Diospyros cordifolia bark on Ehrlich ascites carcinoma-bearing Swiss albino mice

Diospyros cordifolia Roxb. (Ebenaceae), commonly known as Indian ebony, is used traditionally for several medicinal purposes. In this study, the methanol extract of D. cordifolia bark (MEDC) was evaluated for its antitumour effect against Ehrlich ascites carcinoma (EAC)-bearing Swiss albino mice. Twenty-four hours after intraperitoneal inoculation of tumour (EAC) cells in mice, MEDC was administered intraperitoneally at 25 and 50?mg kg?1 bodyweight for 9 consecutive days. On the 10th day, half of the mice were sacrificed to determine the tumour volume, viable and non-viable tumour cell counts, and rest were kept alive for the assessment of median survival time and increase in life span. Haematological profiles were also determined. MEDC exhibited a marked decrease in tumour growth parameters and increased the survival rate of EAC-bearing animals. MEDC normalised the haematological parameters as compared with the EAC control mice. Therefore, this study demonstrated that D. cordifolia bark possessed remarkable antitumour efficacy.     

Clove (Syzygium aromaticum Linn) extract rich in eugenol and eugenol derivatives shows bone-preserving efficacy

This study examined the efficacy of hydroalcoholic extract of dried clove buds, which is rich in phenolic compounds namely eugenol and eugenol derivatives (precursors of flavones, isoflavones and flavonoids), on different primary and secondary osteoporotic marker changes in an ovariectomised (OVX) rat model of osteoporosis. Female Wistar rats were randomly divided into three groups: sham-operated control (A), OVX (B) and OVX plus 50% hydroalcoholic extract of dried clove buds for 4 weeks (C). Results indicated that, compared to control, serum alkaline phosphatase (AP; 48.25%, p?相似文献   

Synthesis and properties of amphiphilic photoresponsive gelators for aromatic solvents

A sugar-based photoresponsive supergelator, N-glycosylazobenzene that shows selective gelation of aromatic solvents is described. The partial trans-cis isomerization of the azobenzene moiety allows photoinduced chopping of the entangled gel fibers to short fibers, resulting in controlled fiber length and gel-sol transition. The gelator is useful for the selective removal of toxic aromatic solvents from water.     

Restricted conformational flexibility of a triphenylamine derivative on the formation of host-guest complexes with various macrocyclic hosts

Herein, we report the host-guest-type complex formation between the host molecules cucurbit[7]uril (CB[7]), β-cyclodextrin (β-CD), and dibenzo[24]crown-8 ether (DB24C8) and a newly synthesized triphenylamine (TPA) derivative 1X(3) as the guest component. The host-guest complex formation was studied in detail by using (1)H?NMR, 2D NOESY, UV/Vis fluorescence, and time-resolved emission spectroscopy. The chloride salt of the TPA derivative was used for recognition studies with CB[7] and β-CD in an aqueous medium. The restricted internal rotation of the guest molecule on complex formation with either of these two host molecules was reflected in the enhancement of the emission quantum yield and the average excited-state lifetime for the triphenylamine-based excited states. Studies with DB24C8 as the host molecule were performed in dichloromethane, a medium that maximizes the noncovalent interaction between the host and guest fragments. The F?rster resonance energy transfer (FRET) process involving DB24C8 and 1(PF(6))(3), as the donor and acceptor fragments, respectively, was established by electrochemical, steady-state emission, and time-correlated single-photon counting studies.