Rare-earth ion doped TeO2 and GeO2 glasses as laser materials

Animesh Jha, Billy Richards, Gin Jose, Toney Teddy-Fernandez, Purushottam Joshi, Xin Jiang, Joris Lousteau

Germanium oxide (GeO2) and tellurium oxide (TeO2) based glasses are classed as the heavy metal oxide glasses, with phonon energies ranging between 740 cm(-1) and 880 cm(-1). These two types of glasses exhibit unique combinations of optical and spectroscopic properties, together with their attractive environmental resistance and mechanical properties. Engineering such a combination of structural, optical and spectroscopic properties is only feasible as a result of structural variability in these two types of glasses, since more than one structural units (TeO4 bi-pyramid, TeO3 trigonal pyramid, and TeO3+delta polyhedra) in tellurite and (GeO4 tetrahedron, GeO3 octahedron) in GeO2 based glasses may exist, depending on composition. The presence of multiple structural moities creates a range of dipole environments which is ideal for engineering broad spectral bandwidth rare-earth ion doped photonic device materials, suitable for laser and amplifier devices. Tellurite glasses were discovered in 1952, but remained virtually unknown to materials and device engineers until 1994 when unusual spectroscopic, nonlinear and dispersion properties of alkali and alkaline earth modified tellurite glasses and fibres were reported. Detailed spectroscopic analysis of Pr3+, Nd3+, Er3+ and Tm3+ doped tellurite glasses revealed its potential for laser and amplifier devices for optical communication wavelengths. This review summarises the thermal and viscosity properties of tellurite and germanate glasses for fibre fabrication and compares the linear loss for near and mid-IR device engineering. The aspects of glass preform fabrication for fibre engineering is discussed by emphasising the raw materials processing with casting of preforms and fibre fabrication. The spectroscopic properties of tellurite and germanate glasses have been analysed with special emphasis on oscillator strength and radiative rate characteristics for visible, near IR and mid-IR emission. The review also compares the latest results in the engineering of lasers and amplifiers, based on fibres for optical communication and mid-IR. The achievements in the areas of near-IR waveguide and mid-IR bulk glass, fibre, and waveguide lasers are discussed. The latest landmark results in mode-locked 2 mu m bulk glass lasers sets the precedence for engineering nonlinear and other laser devices for accessing the inaccessible parts of the mid-IR spectrum and discovering new applications for the future. (c) 2012 Elsevier Ltd. All rights reserved.

Kagome hollow-core photonic crystal fiber probe for Raman spectroscopy

Petru Ghenuche, Silke Rammler, Nicolas Y. Joly, Michael Scharrer, Michael Frosz, Jerome Wenger, Philip St J. Russell, Herve Rigneault

We demonstrate the use of a large-pitch Kagome-lattice hollow-core photonic crystal fiber probe for Raman spectroscopy. The large transmission bandwidth of the fiber enables both the excitation and Raman beams to be transmitted through the same fiber. As the excitation beam is mainly transmitted through air inside the hollow core, the silica luminescence background is reduced by over 2 orders of magnitude as compared to standard silica fiber probes, removing the need for fiber background subtraction. (C) 2012 Optical Society of America

The role of self-trapped excitons and defects in the formation of nanogratings in fused silica

Soeren Richter, Fei Jia, Matthias Heinrich, Sven Doering, Ulf Peschel, Andreas Tuennermann, Stefan Nolte

We investigate the role of self-trapped excitons (STEs) and defects in the formation of femtosecond laser pulse induced nanogratings (NGs) in fused silica. Our experiments reveal strongly enhanced NG formation for pulse separations up to the STE lifetime. In addition, the absorption spectra show that the weaker cumulative action of laser pulses for longer temporal separations is predominantly mediated by dangling-bond-type lattice defects that emerge from decaying STEs. (C) 2012 Optical Society of America

Resonant modulational instability and self-induced transmission effects in semiconductors: Maxwell-Bloch formalism

Oleksii A. Smyrnov, Fabio Biancalana

The nonlinear optical properties of semiconductors near an excitonic resonance are investigated theoretically by using the macroscopic J model [Ostreich and Knorr, Phys. Rev. B 48, 17811 (1993); 50, 5717 (1994)] based on the microscopic semiconductor Bloch equations. These nonlinear properties cause modulational instability of long light pulses with large gain and give rise to a self-induced transmission of short light pulses in a semiconductor. By an example of the latter well-studied effect, the validity of the used macroscopic model is demonstrated, and good agreement is found with both existing theoretical and experimental results.

A 2D Quantum Walk Simulation of Two-Particle Dynamics

Andreas Schreiber, Aurel Gabris, Peter P. Rohde, Kaisa Laiho, Martin Stefanak, Vaclav Potocek, Craig Hamilton, Igor Jex, Christine Silberhorn

Multidimensional quantum walks can exhibit highly nontrivial topological structure, providing a powerful tool for simulating quantum information and transport systems. We present a flexible implementation of a two-dimensional (2D) optical quantum walk on a lattice, demonstrating a scalable quantum walk on a nontrivial graph structure. We realized a coherent quantum walk over 12 steps and 169 positions by using an optical fiber network. With our broad spectrum of quantum coins, we were able to simulate the creation of entanglement in bipartite systems with conditioned interactions. Introducing dynamic control allowed for the investigation of effects such as strong nonlinearities or two-particle scattering. Our results illustrate the potential of quantum walks as a route for simulating and understanding complex quantum systems.

Laser propulsion of microparticles in hollow-core photonic crystal fiber: a review of recent developments

T. G. Euser, O. A. Schmidt, M. K. Garbos, S. Unterkofler, P. St. J. Russell

We review our recent work on laser propulsion of microparticles in hollow-core photonic crystal fibers (HC-PCF).

Molecular Gating of Silicon Nanowire Field-Effect Transistors with Nonpolar Analytes

Yair Paska, Thomas Stelzner, Ossama Assad, Ulrike Tisch, Silke Christiansen, Hossam Haick

Silicon nanowire field-effect transistors (Si NW FETs) have been used as powerful sensors for chemical and biological species. The detection of polar species has been attributed to variations in the electric field at the conduction channel due to molecular gating with polar molecules. However, the detection of nonpolar analytes with Si NW FETs has not been well understood to date. In this paper, we experimentally study the detection of nonpolar species and model the detection process based on changes in the carrier mobility, voltage threshold, off-current, off-voltage, and subthreshold swing of the Si NW FET. We attribute the detection of the nonpolar species to molecular gating, due to two Indirect effects: (i) a change in the dielectric medium close to the Si NW surface and (ii) a change in the charged surface states at the functionality of the SI NW surface. The contribution of these two effects to the overall measured sensing signal is determined and discussed. The results provide a launching pad for real-world sensing applications, such as environmental monitoring, homeland security, food quality control, and medicine.

Sub-kHz Linewidth of Crystalline Whispering Gallery Mode Resonator Stabilized Ring-Laser

M. Collodo, B. Sprenger, F. Sedlmeir, S. Svitlov, H. G. L. Schwefel, L. J. Wang

Sub-kHz lasing linewidth of a CaF2 whispering gallery mode (WGM) resonator passively stabilized ring laser has been observed. A detailed frequency analysis including a three-cornered-hat measurement yields a linewidth of 643Hz. (C) 2011 Optical Society of America

Continuously adjustable narrow-band heralded single photon source

Michael Foerstch, Josef Fuerst, Christoffer Wittmann, Dmitry Strekalov, Andrea Aiello, Christine Silberhorn, Christoph Marquardt, Gerd Leuchs

We present the high efficient generation of narrow-band heralded single photons, widely tunable in wavelength and bandwidth using resonator enhanced spontaneous down conversion in a crystalline whispering gallery mode resonator. (C) 2011 Optical Society of America

Recent Progress in Nonlinear Optomechanics in Micro structured Optical Fibers

Myeong Soo Kang, Anna Butsch, Philip St. J. Russell

We will present our recent progress in nonlinear optomechanics in a platform of microstructured optical fibers. By tightly confining transverse mechanical motion and guided laser light simultaneously in a micron-sized glass fiber core, we have successfully demonstrated novel types of nonlinear optomechanical effects at modest optical powers, thanks to the strongly enhanced optomechanical interactions. We will describe the principles, characteristics and potential applications of the effects.