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

Preface.Introduction.Chapter 1. Selected Topics in Electromagnetic Wave Propagation.1.1. Maxwell's Equations and the Fundamental Fields.1.2. Electromagnetic Wave Propagation in Sourceless Media.1.3. Power Transmission.1.4. Group Velocity.1.5. Reflection and Transmission of Waves at Plane Interfaces.1.6. Material Resonances and Their Effects on Wave Propagation.Problems.References.Chapter 2. Symmetric Dielectric Slab Waveguides.2.1. Ray Analysis of the Slab Waveguides.2.2. Field Analysis of the Slab Waveguides.2.3. Solutions of the Eigenvalue Equations.2.4. Power Transmission and Confinement.2.5. Leaky Waves.2.6. Radiation Modes.2.7. Wave Propagation in Curved Slab Waveguides.Problems.References.Chapter 3. Weakly-Guiding Fibers with Step Index Profiles.3.1. Rays and Fields in the Step Index Fiber.3.2. Field Analysis of the Weakly-Guiding Fiber.3.3. Eigenvalue Equation for LP Modes.3.4. LP Mode Characteristics.3.5. Single Mode Fiber Parameters.3.6. Derivation of the General Step Index Fiber Modes.Problems.References.Chapter 4. Loss Mechanisms in Silica Fiber.4.1. Basic Loss Effects in Transmission.4.2. Fabrication of Silica Fibers.4.3. Intrinsic Loss.4.4. Extrinsic Loss.4.5. Bending Loss.4.6. Source-to-Fiber Coupling.Problems.References.Chapter 5. Dispersion.5.1. Pulse Propagation in Media Possessing Quadratic Dispersion.5.2. Material Dispersion.5.3. Dispersion in Optical Fiber.5.4. Chromatic Dispersion Compensation.5.5. Polarization Dispersion.5.6. System Considerations and Dispersion Measurement.Problems.References.Chapter 6. Special Purpose Index Profiles.6.1. Multimode Graded Index Fiber.6.2. Special Index Profile Optimization.Problems.References.Chapter 7. Nonlinear Effects in Fibers I: Non-Resonant Processes.7.1. Nonlinear Optics Fundamentals.7.2. Nonlinear Phase Modulation on Pulses.7.3. The Nonlinear Schrodinger Equation.7.4. Additional Non-Resonant Processes.Problems.References.Chapter 8. Nonlinear Effects in Fibers II: Resonant Processes and Amplification.8.1. Raman Scattering.8.2. Stimulated Brillouin Scattering.8.3. Rare-Earth-Doped Fiber Amplifiers.Problems.References.Appendix A: Properties of Bessel Functions.Appendix B: Notation.Index.

Fundamentals of optical fibers

Conservation agriculture is an approach to management of agro-ecosystems for improved and sustainable productivity, thereby conserving natural resources and the environment. It uses minimal soil disturbance (no tillage) and permanent soil cover (mulch) as sustainable cultivation practices for the future. In Algeria, conservation agriculture was introduced only about 10 years ago. In this study, plough tillage (PT), reduced tillage (RT) and no-till (NT) were evaluated regarding their effects on physical, chemical and microbiological soil parameters in an on-farm research approach in two agricultural regions of Algeria (Annaba and Sétif) with differing site and agricultural soil management conditions. Soil samples were taken from fields on commercial farms, at Annaba on soils containing mainly recent clayey alluvium in a Mediterranean climate and at Sétif on soils with limestone rock parent material and a semi-arid continental Mediterranean climate. The interactions between soil structural properties and microbial biomass and activities were examined using disturbed and undisturbed soil samples collected on two occasions from the top 20 cm of soil in all three tillage systems. The results showed a generally intensive loosening effect of PT compared with RT and NT, which led to lower bulk density and higher porosity. The parameters macroporosity and air permeability demonstrated that the air-filled pore space in the topsoil differed in its transport efficiency between the tillage systems, with rather random organisation in PT and RT and a more continuous arrangement in NT. Structural stability of the topsoil layer and its resistance to compaction was inversely correlated with tillage loosening intensity. The content of tot-C and tot-N showed significant correlations between in the two regions and all tillage systems. Comparable differences between tillage systems and regions for tot-C and the C/N ratio in the entire set of samples suggest that more input of new, litter-derived organic matter with large C/N ratios promotes larger tot-C concentrations in the study two site. These results of C/N ratio indicate that we have a good mineralization of the SOM in RT, NT and PT successively for the two regions, but in Annaba, it was good and fast on the surface and takes a slow regime at depth, but the Sétif mineralization was slow and only returns a small amount of mineral nitrogen to the soil. Two microbiological parameters, biomass and basal respiration, were positively affected by RT and showed a distinct effect of sampling date, with the highest values observed shortly after tillage. Site-specific effects were also observed. Based on the results, it was not possible to identify an ideal tillage system associated with only positive effects on soil quality parameters, but it seems to be the TCS have been identified as an optimal tillage system for the regions studied. These preliminary results from on-farm research are of a tentative nature and must be confirmed in further studies in order to deliver reliable recommendations for farmers in Algeria.

I. Introduction générale

The spectroscopic properties and thermal stability of Er2O3 doped Bi2O3–B2O3–Na2O glasses are investigated experimentally. A close correlation is observed between the B2O3 content and the spectroscopic properties such as Judd–Ofelt intensity parameters Ωt (t=2,4,6), emission spectra, and lifetime of 4I13/2 level of Er3+. The value of Ω6 increases with an increase of B2O3 content, which is attributed to the decrease of the covalency of Er–O bond in terms of the glass microstructure and electronegativity theory. The emission spectra of 4I13/2→4I15/2 transition broadens as a consequence of the enhancement of the inhomogeneous distribution of Er3+ sites when increasing B2O3 content. The lifetime of 4I13/2 level of Er3+ in bismuth-based glass, compared with those in other glasses, is relative low due to the high-phonon energy of the B–O bond, the large refractive index of the host, and the existence of OH− in the glass. In addition, the glass stability is improved in which the substitution of B2O3 for Bi2O3 st...

Spectroscopic properties and thermal stability of erbium-doped bismuth-based glass for optical amplifier

Dielectric constant e ′ , loss tan δ and ac conductivity σ ac of 40CaO– x WO 3 –(60− x )P 2 O 5 (with 0⩽ x ⩽15) glasses are studied over a range of frequencies and temperature. The dielectric breakdown strength of these glasses is also determined at room temperature. The values of dielectric parameters, viz., e ′ , tan δ and σ ac of CaO–P 2 O 5 glasses are found to decrease with the introduction of WO 3 up to 3 mol% and increase with further increase in the concentration of WO 3 ; the probable reasons for such an increase are identified and explained with the aid of IR spectra and differential thermal analysis of these glasses. The variation of tan δ with temperature at different frequencies of CaO–P 2 O 5 glasses has exhibited dielectric relaxation effects with decreasing relaxation intensity with increase in the concentration of WO 3 from 0 to 3 mol%; such relaxation effects seem to have been absent in glasses containing WO 3 beyond 3 mol%. The relaxation phenomenon has been analysed by a pseudo-Cole–Cole plot method and the possible mechanism responsible for such relaxation effects has been suggested.

Study of CaO–WO3–P2O5 glass system by dielectric properties, IR spectra and differential thermal analysis

The effect of the types of alkaline earth metal ions (Mg2+, Ca2+ and Ba2+) and concentration of Al2O3 and BaO on the refractive index and the effective emission linewidths of the 4I13/2−4I15/2 transition of Er3+ ions in phosphate glasses, 64P2O5 · 12Al2O3 ·  3.5( Er 2 O 3 + La 2 O 3 )·20.5 MO ( M = Mg , Ca , Ba ) and 64P2O5 · 3.5(Er2O3+La2O3) · (21.5 − x)Al2O3 ·  (11+x) BaO (x=0,3.5,6.5 and 9.5) , were investigated. A single mode Er3+ doped phosphate glass fiber with a core diameter of 4 μm was fabricated by the rod-in-tube technique. A new Er3+ doped fiber amplifier is demonstrated pumping with a 980 nm fiber pigtailed-laser diode. A gain per unit length greater than 2 dB/cm is demonstrated, which is the largest gain per unit length for fiber amplifiers to our knowledge.

Fred Smekatala

Papers

Er3+-doped phosphate glasses for fiber amplifiers with high gain per unit length