Biography:

Linganna K received M.Sc  and Ph.D degrees from the Department of Physics, Sri Venkateswara University, Tirupati, Andhra Pradesh, India in 2006 and 2012, respectively. His research activities involve preparation and characterization of rare earth doped glasses and glass fibers fabricated by melt quenching technique and fiber drawing processes, respectively, for the development of photonic devices such as lasers, optical amplifiers, sensors and so on. He also gained experience on waveguide inscription in rare earth doped glasses indigenously developed at Sri Venkateswara University, Tirupati, India for integrated optics. So far, he visited UK, Mexico for his Doctoral and Post-Doctoral research work. For the past five years, he has been working as a Post-Doctoral researcher in South Korea. He published his research work in international reputed journals besides presented his work in various international and national conferences/workshops/symposia.

Abstract:

Statement of the Problem: For the past decades, erbium doped fiber amplifier (EDFA) has become a key element of modern telecommunication system due to Er³⁺ ion emission at 1.53 mm attributed to the ⁴I_13/2 → ⁴I_15/2 transition [1, 2]. The commercial EDFAs used in communication networks are made up of silica glass that has a relatively narrow bandwidth emission (~35 nm) resulting in a narrow gain curve, which limits its applications to meet broadband transmission. Among different host matrices, fluorophosphate (FP) glasses have received great interest for laser and optical amplifier applications because of their characteristic properties [3, 4]. Therefore, Er³⁺-doped FP glasses can enlarge the emission cross-section and improve luminous efficiency because of the characteristic features of Er³⁺ ions and advantageous properties of mixed fluoride and phosphate glasses [5]. Hence, the present study carried out spectroscopic studies on Er³⁺-doped FP glasses for different concentrations of Er³⁺. Methodology: Er³⁺-doped fluorophosphate glasses were prepared by a conventional melt quenching technique and were characterized through spectroscopic techniques. Findings: From absorption, emission and decay measurements, the important spectroscopic properties such as bandwidths, emission cross-sections and lifetime were evaluated for significant 1.53 mm emission band. The emission cross-section and lifetime were found to be of the order of 2.0´10^-20 cm² and 10 ms, respectively. These desirable parameters are used to see the potentiality of the material for laser gain media. Conclusion & Significance: It was concluded that higher dopant Er concentration improved the 1.53 mm emission band characteristic properties. The results indicate that this glass composition can enable construction of short, highly efficient fiber or planar waveguide amplifiers.

Biography:

Hong Gao’s research interests are in quantum optics and quantum information. Specifically he focuses on the coherent and nonlinear interaction of light with atomic ensembles, such as slow light, light storage, laser cooling and four-wave mixing. He is interested in studying the fundamental physical basis during these interactions and would like to expand them for quantum information processing and quantum computation.

Abstract:

Quantum coherence has been explored in many interesting phenomena in the past two decades. Quantum coherence occurring in the interaction between light and atoms, can be produced by two orthogonal polarized laser beams coupling with a three-level system. Atoms simultaneously exposed by two overlapping laser beams generate a coherent state, which can make one of these laser beams transmit without any absorption. Coherent population transfer among quantum states of atoms and molecules has also been studied, which is named stimulated Raman adiabatic passage (STIRAP). The procedure of STIRAP relies on the initial creation of a coherence with subsequent adiabatic evolution. Xiao et al. observed this phenomena of atomic coherence production at one position and recovered the coherence at another location. So far, no experiment has shown that the atomic coherence can be generated with two spatially separated laser beams. Here, we experimentally investigate pattern formation with a hybrid vector beam (VB) passing though rubidium vapor. Specifically, we generated a hybrid VB using a Q-plate and a quarter wave plate. We observe that the hybrid VB can form a four-petal pattern upon passing through the atomic medium and the pattern can be controlled from four-petal to two-petal by varying the bias magnetic field. The maximum transmitted total intensity occurs in zero magnetic field. The mechanism for the pattern formation can be interpreted by the generation of atomic coherence. We perform a second experiment with two orthogonal circularly polarized laser beams to show that the atomic coherence can be generated with two spatially separated beams. A basic model including absorption and quantum coherence provides good agreement with the experimental results. Our results may have applications in optical manipulation, measurement of magnetic fields, and studying quantum coherence in atomic ensembles.

Biography:

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Biography:

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