High-speed picosecond optical pulse compression from gain-switched 1.3-µm distributed feedback-laser diode (DFB-LD) through highly dispersive single-mode fiber

Picosecond optical pulse compression characteristics of chirped pulses from gain-switched distributed feedback-laser diodes (DFB-LD) transmitting through highly dispersive media are studied theoretically and experimentally. It is clarified theoretically that gain-switched chirped pulses can be compressed to about a 0.7-time bandwidth product by normal dispersion of the dispersive media and that the optimum dispersion value to obtain a minimum compressed pulse is proportional to the square of original pulsewidth. Through a dispersion, shifted single-mode fiber with -48-ps/nm normal dispersion at a 1.3-μm wavelength, gain-switched 30-ps (FWHM) pulses from a directly modulated 1.3-μm DFB-LD at a 4.4-GHz repetition rate have been successfully compressed to 6.4-ps optical pulses with a 0.86-time bandwidth product. Experimental results agree with the theoretical analysis.     

The central limit theorem under the absence of extremal absolute order statistics

One finds conditions for the relation are the absolute order statistics for a repeated sample from a symmetric distribution.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 142, pp. 59–67, 1985.     

Spectrophotometric study of holmium complexation in KOH solutions at 25°C

The complexation of Ho³⁺ in HoCl₃ and KOH solutions at 25°C and saturated vapor pressure was studied by an indicator spectrophotometric technique, and the pH values of the investigated solutions were determined. The stability constants of the hydroxo complexes of Ho³⁺ were measured over a range of pH 9.25–10.10 and at μ≤ 4 × 10^?4 and extrapolated to zero ionic strength.     

8-Gbit/s transmission experiment over 68 km of optical fiber using a Ti:LiNbO3external modulator

We describe the performance of an experimental 1.5-μm lightwave transmission system operating at 8 Gbit/s over 68.3 km of single-mode fiber. The dispersion penalty is limited to 1 dB through the use of external modulation and is attributable to the intrinsic information bandwidth.     

The limit distribution of the maximal deviation of a spline estimate of a probability density

One finds the limit distribution of the maximum absolute value of the normalized deviation of a spline estimate from an unknown probability density.Translated from Veroyatnostnye Raspredeleniya i Matematicheskaya Statistika, pp. 447–467, 1986.     

Kondo lattice and heavy fermions in Heusler phases: CeInAg2−xCux

Magnetic properties, electrical resistivity, specific heat and magnetic excitations have been investigated in Heusler phases CeInAg_2–xCu_x. The hybridization continuously increases from CeInAg₂ (antiferromagnetic Kondo lattice) to CeInCu₂ (heavy fermion compound). The specific heat coefficient for this last compound is found to reach 1.2 J/mole. K² at 1.4 K, the Kondo temperature is 6 K and the Wilson ratio is close to 2.     

Spectral characterization of a tunable alexandrite laser by rubidium absorption at 780 nm

Rubidium vapor was used to characterize the output of a tunable, pulsed alexandrite laser operating at 780 nm. Rubidium spectra were obtained at temperatures of 23, 50, 110, and 140°C. Excellent agreement was obtained with computer-synthesized spectra which yielded values for the effective laser bandwidth at different operating conditions. The model assumed a Voigt profile for the rubidium5^{2}P_{3/2} leftarrow 5^{2}S_{1/2}transition and a Gaussian profile for the laser pulse. The model also showed that the laser output was spectrally compact with no evidence of energy outside the narrow 780 nm central feature.     

Immersive electronic books for surgical training

Immersive electronic books (IEBooks) for surgical training will let surgeons explore previous surgical procedures in 3D. The authors describe the techniques and tools for creating a preliminary IEBook, embodying some of the basic concepts.