PACS 42.50.Gy -Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption PACS 42.50.Ct -Quantum description of interaction of light and matter; related experiments Abstract -An experimental investigation of a Microwave Optical Double Resonance (MODR) phenomenon is carried out in a four level N system of 85 Rb atoms, at room temperature. This N system consists of a closed three level Λ subsystem irradiated with two optical fields and one microwave field. The MODR response is investigated in a separate probe field which drives a resonant transition from one of the ground states of the Λ system to a fourth level. We find that, under two-photon resonance condition for the optical fields, the MODR becomes a function of the relative phase between the beat frequency envelop of the optical fields and the microwave field. The variation in MODR is shown to be correlated with the phase-sensitive variation of the EIT phenomenon seen in such microwave-connected closed Λ systems. We envisage that this phasesensitive variation in the MODR, can be utilized for a phase-sensitive manipulation of non-linear optical phenomena in N systems.
Multi-level gaseous atomic systems showing electromagnetically induced transparency (EIT) phenomenon also exhibit low light intensity nonlinear optical phenomena. This is primarily due to the supression of linear susceptibility for the probe light during EIT. Therefore under EIT, nonlinear interactions become appreciable even at very low light intensities. In particular, Kerr nonlinearity in N systems irradiated by three fields has been both experimentally and theoretically investigated. In this paper, we report an all optical observation of an absorptive three-photon resonance feature, of subnatural width, in a N level scheme of gaseous rubidium, at room temperature, in a novel geometry of three independent beams. The non-Doppler free configuration of the beam in which the absorption is seen is the first such feature reported in a beam that is not directly taking part in the transparency effect. We have demonstrated the velocity selective nature of this absorption and studied the contrast dependence on detuning from the fourth level. Density matrix calculations have been carried out for this geometry, the results of which are in qualitative agreement with the experiment.
For the past few decades, substantial progress has been made in material properties and construction methodology, which demands in need of development of stronger and lighter members in structural steel applications. The demands of increase in strength and reduction in weight of sections leads to development of structures which are slender and also stability plays a major role in design. The main goal of this study is to develop and investigate the performance of build-up steel I beam sections with corrugated webs. This study focuses on analysis of flexural behaviour and failure modes of plain web, rectangular, trapezoidal web and triangular web in beams by experimental investigations using three-point load test and analytical investigations using ANSYS software. From experimental and analytical analysis, triangular corrugated web beam performs better compared to all section. The experimental results obtained are more similar to analytical results obtained by ANSYS software with only slight deviations. The failure modes in both experimental investigation and analytical analysis are similar.
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