Wavelength stabilized 980 nm uncooled pump laser modules for erbium-doped fiber amplifiers

We review the development of wavelength stabilized 980 nm pump laser modules without active temperature stabilization for applications in erbium-doped fiber amplifiers. Operation over a wide temperature range with an output power exceeding 400 mW at an ambient temperature of 70°C is demonstrated. The overall reliability of uncooled modules is estimated to be well below 500 FIT at all operating conditions. Such devices are made possible by continuous development and steady improvement of the pump laser chip, the optimization of the fiber Bragg grating stabilization scheme, careful design of the module package, and extended reliability analysis on the basis of stress tests as well as field data.     

Small Deformation Measurements of Diffuse Objects: Phase Stepping by Frequency Drift of a He-Ne Laser

We describe a simple phase-stepping speckle interferometer with large path difference, in which phase modulation is achieved by thermal frequency drift of the He-Ne light source. This system is easy to set up, requires no specialised components, is immune from the effects of piezo actuator hysteresis, and is capable of producing phase maps in which the noise is less than 1/20λ.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27-29, Saitama, Japan.     

Phase transition and phonon-drag conductivity in quasi-unidimensional systems

We investigate the properties of a quasi-unidimensional system which exhibits Peierls instability at T_c(μ), where μ is the Fermi energy as measured from the middle of the conduction band. T_c(μ) decreases as 6μ6 increases. The phonon-drag diagrams contribute to fluctuation conductivity, which is proportional to $\text{(T ? T}{}_{\mathrm{c}}\text{)}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$, if |μ| > 1.056 T_c(0). The Kohn Anomalies do not occur at 2k_F unless μ = 0 or |μ| ? T.     

The rameses algorithm for multiple equilibria-II Some further developments

The algorithm RAMESES has been made more efficient by incorporation of additional procedures: to extrapolate to the next point by an exact polynomial of any desired order, to control the gain on the adjustment of each independent species, and to optimize the initial guess. The need to consider electroneutrality is emphasized, and some problems with convergence criteria and synthetic test systems are discussed. Some conditions for objective algorithm testing are proposed.     

Ring-opening and a novel ring expansion in the reactions of 1-Alkyl-2-carbomethoxyazetidine with hydrazine

The mechanism of the reactions of 1-t-butyl-2-carbomethoxyazelidine and 1-benzyl-2-carbomethoxyazetidine with hydrazine hydrate was investigated. Treatment of 1-alkyl-2-earbomethoxyazetidine with hydrazine hydrate in cold ethanol yielded 1-alkylazetidine-2-carhohydrazide. Depending on the sterie bulkiness of the alkyl group of the amino functionality, reactions of 1-alkylazetidine-2-carbohydrazides in methanol gave the appropriate aminoester or the appropriate pyrrolidone, or a mixture of both. The intermediacy of the diimide in these transformations was confirmed by the concurrent reduction of azobenzene to hydrazobenzene.     

Group-valued modular functions

Modular functions on a lattice (m(x)+m(y)=m(x∪y)+m(x∩y)) live on modular lattices in that they are induced by modular functions on a quotient modular lattice. Those which identify pairs of the distributive inequality live on distributive lattices in the same sense. The structure of all modular functions on a lattice of finite height is determined. The “distance function” derived by Kranz from a modular function is shown to satisfy the triangle inequality. Presented by E. Nelson.     

Covariance measurements in the initial region of an annular jet

This paper describes the results of correlation measurements in the initial region of a basic annular jet, which is under the effect of the jet vortices and of the wake induced vortices. Evidence has been found that the wake induced vortices are excited by the disturbances associated with the wake vortices. For these wake induced vortices the azimuthal constituent (m = 1) is dominant. The similarity observed between the behaviour of the jet vortices and that of the wake induced vortices suggests that the jet vortices are also excited by these disturbances of the wake vortices, having the same Strouhal number. Thus the jet vortices are also dominated by the azimuthal constituent (m = 1). However, evidence has been found that within the first two outer diameters an axisymmetrical constituent (m = 0) is also present within the jet vortices. Comparison of the wake induced vortices with the jet vortices shows that these two helical waves are out of phase and are axially separated.     

Determination of the appearance potentials of [C3H7]+ ions by a computerized electron distribution difference procedure

A simple computerized electron distribution difference method has been developed using a conventional mass spectrometer and an on-line computer. Using the system, ionization potentials for various propyl halides were measured and found to agree well with photoionization data. The appearance potentials for [C₃H₇]⁺ agreed well with literature values, except for 1-propyl bromide and 1- propyliodide which gave values approximately 0.7 eV lower than previous reports. The results are interpreted to indicate threshold formation of the sec-propyl ion from all propul halides.