Ultrashort Pulse Amplification at 1080 nm With a Long-Wavelength InGaAs–GaAs Flared Amplifier

Pulses of 5 ps in duration have been amplified using a long-wavelength InGaAs-GaAs semiconductor optical amplifier containing a flared waveguide. The amplifier is seeded using short pulses emitted by a passively mode-locked semiconductor laser. Average output powers of 50 mW have been obtained at a center wavelength of 1080 nm for a drive current of 290 mA. Pulse compression yields durations as short as 520 fs and peak powers as high as 40 W. Perspectives for combining the semiconductor master oscillator power amplifier with Yb fiber amplifiers in a hybrid configuration are also briefly discussed.     

Effect of selected impurities on the continuous precipitation of calcium sulphate (gypsum)

The effects of selected cationic and anionic impurities on the precipitation of gypsum in aqueous brine have been studied in a continuous MSMPR crystalliser. Crystal size distributions, determined by in situ Malvern laser light-scattering measurements, were found to be bimodal. The suspected presence of agglomerates was confirmed by microscopy. Aluminium and maleate ions both enhanced the degree of agglomeration, but reduced the overall growth and nucleation rates. Contrary to expectation, fumarate ions also exerted an observable effect on both agglomeration and crystal growth.     

Ultrashort optical pulse generation with a mode-locked long-wavelength (1075-1085 nm) InGaAs-GaAs semiconductor laser

Optical pulses are generated by passive and hybrid mode-locking of a long wavelength (1075-1085 nm) InGaAs-GaAs ridge waveguide laser grown by gas source molecular beam epitaxy. The devices are fabricated with two sections, one of which contains a bend in the waveguide for coupling to an external linear cavity. Pulses 2-5 ps in duration have been generated with average powers ranging from 750 /spl mu/W to 1.8 mW. Pulse compression yields durations as short as 570 fs. Post amplification with a narrow stripe InGaAs-GaAs semiconductor optical amplifier increases the average output power up to 13 mW.     

Structural State of Steel Plates under the Action of Moving Heat Sources

We develop a procedure for the analysis of the phase composition of thin steel plates subjected to the action of distributed moving heat sources with several centers of localization. It is shown that the proper choice of the intensity and location of the centers of heating makes it possible to halve the maximum content of martensite and substantially decrease the nonuniformity of its space distribution in the zone of thermal influence.     

Residual Structural Stresses in a Steel Body

We develop a mathematical model for the evaluation of residual structural stresses in steel products. The proposed computational model is based on the relations of the statistical theory of phase composition of low-alloy steels in the process of rapid cooling. The distributions of residual stresses are determined for bars of 15KhM steel with square and rectangular cross sections.