H. van Tongeren

Phase-change optical data storage in GaSb.

The amorphous to crystalline transition in the semiconductor GaSb has been studied as a recording mechanism for write-once optical storage. Amorphous as-deposited films, 100 nm thick, are transformed locally to the crystalline state by a focused laser beam. This recording process can be accomplished within 10 ns. The dimensions of the crystalline marks can be accurately controlled. Optical storage media based on GaSb are suitable for the archival storage of information modulated according to the compact disk format.

Positive column of the Cs–Ar low‐pressure discharge

A model for the positive columns of dc low‐pressure discharges in Cs–Ar mixtures, which includes radial depletion of Cs ground‐state atoms and radiation trapping, is presented. The available experimental data for this discharge system were extended in such a way that comparison could be made between model calculations and experiments for a wide range of discharge currents and Cs vapor densities (0.2 × 1019−3.0 × 1019 m−3) and a reasonable agreement is obtained.

Positive column of Na–Ar and Na–Ne–Ar dc low‐pressure discharges

Measurements are reported of the electron temperature, electric field, and electron density in the positive column of low‐pressure Na–Ar and Na–Ne–Ar dc discharges. The production of light at the sodium D resonance lines was also measured. The experimental data were obtained for a tube radius of 1.4 cm, and a noble gas filling of 10 Torr. The sodium density varied from 1×1019 to 6×1019 m−3, and the discharge current from 0.1 to 3.0 A. Depletion of sodium ground‐state atoms was found to have a decisive effect on the discharge properties at the higher discharge currents. Calculations on a model of the discharge were performed in addition to the measurements. In this model deviations from the Maxwell electron energy distribution were included. The results of the calculations for the electron temperature as a function of current were found to be in good agreement with the experimental data. However, the calculated electric field as a function of current showed qualitative agreement only.

A small coaxial laser module for the Gb/s transmission-speed range

A coaxial laser module based on a small CD laser header is described. The module has a diameter of 5.6 mm and a length of 14 mm. By modifying the standard CD laser header the electrical performance could be up-graded to a 5 GHz bandwidth. The coupling optics is designed for low feedback and includes an optical isolator. Coupling efficiencies up to 80% have been achieved. >

Thermal aspects of pump-laser packaging

A modified DIL-14 (dual in line-14) package for a pump-laser diode emitting at a wavelength of 1480 nm is described. By improving the thermal resistance of the housing, a thermal power of 1 W can be dissipated in the laser crystal. The mounting surface of the crystal assembly can be kept at 25 degrees C by a Peltier cooler operating at a current of 1 A for 65 degrees C ambient temperature. Under these conditions more than 60 mW is launched into the fiber pigtail.<<ETX>>

Measured and calculated Cs excited‐state densities in Cs–Ar low‐pressure discharges

Radial distributions of the 62P excited‐state density of Cs in low‐pressure Cs–Ar discharges have been measured by means of absorption from a continuum in the 876.1‐ and 917.2‐nm lines of Cs. The variation of the excited‐state densities with the discharge current has also been studied. The experimental data are compared with results of calculations based on a model of the positive column of the Cs–Ar discharge in which radiation trapping is taken into account.

Electron temperature and radial density distribution of Cs ground-state atoms in the positive column of a CsAr D. C. low pressure discharge

Abstract The properties of the CsAr positive column are calculated numerically under conditions where depletion of the Cs ground state atoms cannot be neglected. The results are compared with experimental data and a reasonable agreement is obtained.

Packaging of fibre-optic communication lasers for the Gb/s range

A package for a DFB (distributed feedback) laser with integrated optical isolator is described. The design is based on a modular set-up: a laser module provided with a short ferruled pigtail is combined with an optical isolator module with the device fiber pigtail. Laser feedback due to reflections in the isolator module is avoided by slanting the collimated beam through the isolator. An advantage of the design is that both modules can be tested separately. Tests in a 2.5-Gb/s system show that proper data transmission is maintained over a 100-km fiber link despite a deliberately imposed back-reflection at a level of 10%. A bit error rate of 10/sup -10/ at 10% laser feedback is obtained for -31 dBm detector power.<<ETX>>