Day 1 :
- Laser Systems | Optics and Lasers in Medicine | Optoelectronics
Korea Photonics Technology Institute
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.
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 4I13/2 → 4I15/2 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 . 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.
Xi’an Jiaotong University, Xi’an 710049, China
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.
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.
Soochow University, Suzhou 215006, Jiangsu, China
Xiao Yuan is a professor of School of Optoelectronic Science and Technology, Soochow University, China. He received the BA degree in physics and the PhD degree in optics from Sichuan University. From 1982 to 2002, he worked in Northwest Institute of Nuclear Technology, and was a professor at Huazhong University of Science and Technology from 2002 to 2009, China. He joined Soochow University in 2009, and his current research includes advanced lasers, micro- and nano-meter fabrication and laser interferometry, etc.
Laser amplifier has been widely used in the field of scientific research, laboratory astrophysics and inertial confinement fusion (ICF), etc. The multi-pass amplifier (MA) is widely used in high-power laser systems such as ICF drivers, which requires expensive preamplifier systems to compensate for the limited gain of the main amplifiers. Besides, the laser system in MA should operate at high fluence to achieve high extraction efficiency, which results in a technical challenge in the damage of optical components under high-power lasers irradiation.
To efficiently extract the stored energy with low injection energy at low laser fluence operation and make the system compact, a bidirectional ring amplifier (BRA) with twin pulses is proposed. The characteristics of the bidirectional ring amplifier on energy flow, extraction efficiency and output energy capability are studied. The simulation results show that an extraction efficiency of 62.3% at the B integral limit can be obtained at low average fluence of 10.3 J/cm2 and the low injection energy of 3.9 mJ in the bidirectional ring amplifier. The output performance of the bidirectional ring amplifier with twin pulses is demonstrated. The injection energy of the twin pulses is 0.29 mJ and 0.32 mJ at the pulse width of 3 ns (FWHM), and the maximum output energy of the two pulses from BRA is 347 mJ and 351 mJ, respectively. Compared to the effective efficiency extraction of 32% in ring amplifier with single pulse, the maximum extraction efficiency of stored energy in BRA with twin pulses is 60% under the same operation condition. The bidirectional ring amplifier is more compact and the extraction efficiency is much higher at low laser fluence operation, which is beneficial to reduce the effects of nonlinear phase shift. Moreover, the preamplifier for BRA is simple, only a fiber oscillator and a regenerative amplifier can work.