Hybrid glass substrates for waveguide device manufacture.

Hybrid glass substrates were prepared by a novel, low-temperature process joining active (Er-Yb codoped) and passive phosphate glass. The resulting hybrid substrates are chemically and physically robust; they can be cut, ground, and polished by conventional, water-based techniques. The entire substrate can be immersed in a molten-salt bath to produce waveguides simultaneously in the active and passive regions. A low reflectance of -34+/-2 dB was measured at the joint interface with 1531.2-nm light by optical low-coherence reflectometry. Further, a hybrid laser waveguide device exhibited a slope efficiency of 33% at 1540 nm when pumped at 975 nm.

Design and optimization of a diode-pumped fiber-coupled yb:er glass waveguide laser.

An adaptive simulated annealing optimization algorithm is used to derive laser rate equation and waveguiding models with which the best design for a diode-pumped fiber-coupled, Yb:Er glass waveguide laser can be determined. Material parameters that correspond to commercially available laser-glass and diode-pump sources are used in this study. Given a continuous-wave 300-mW pump at 977 nm, approximately 48 mW of power at 1540 nm can be coupled into the LP(01) mode of an optical fiber. Fabrication and alignment tolerance analyses are presented.

Measurements of oxygen concentration of air within totally encapsulating chemical-protective suits.

This study measured oxygen concentrations of air within totally encapsulating chemical-protective (TECP) suits during simulated hazardous materials emergency response operations. This was done to allow assessment of the suitability of use of air within TECP suits as an emergency air supply during escapes from contaminated areas following loss of primary air supply. Samples of air were extracted through a probe installed in TECP suits while the suits were worn during simulated hazardous materials control operations. Data on oxygen concentration were obtained using direct reading equipment and through Orsat analysis of samples. Results indicate that the air within a TECP suit becomes significantly oxygen-deficient soon after the suit is closed, but generally maintains oxygen concentrations somewhat above those known to produce significant physiological effects. However, due to the further reduction of oxygen content inherent in breathing the air within TECP suits, it is anticipated that symptoms of oxygen deficiency sufficient to impair escape could be experienced in some instances. Recommendations are made for modifying current training practices to better prepare personnel working in Level A chemical-protective ensembles to cope with loss of air supply.

Ion-exchanged waveguide lasers in Er3+/Yb3+ codoped silicate glass.

We investigated an Er(3+)/Yb(3+) codoped silicate glass as a host material for waveguide lasers operating near 1.5 microm. Spectroscopic properties of the glass are reported. Waveguide lasers were fabricated by K(+)-ion exchange from a nitrate melt. The waveguides support a single transverse mode at 1.5 microm. An investigation of the laser performance as a function of the Yb:Er ratio was performed, indicating an optimal ratio of approximately 5:1. Slope efficiencies of as great as 6.5% and output powers as high as 19.6 mW at 1.54 microm were realized. The experimental results are compared with a waveguide laser model that is used to extract the Er(3+) upconversion coefficients and the Yb(3+)-Er(3+) cross-relaxation coefficients. The results indicate the possibility of obtaining high-performance waveguide lasers from a durable silicate host glass.

Waveguide polarizers processed by localized plasma etching.

We develop a downstream localized plasma-etching process that permits in situ monitoring of light throughput in a semiconductor-clad channel waveguide as the semiconductor thickness is trimmed. Hydrogenated amorphous silicon films are deposited on ion-exchanged channel waveguides by plasmaenhanced chemical vapor deposition. We then employ the localized plasma-etching process to maximize accurately the extinction ratio between TE and TM polarizations propagating in the clad waveguide. We achieve polarization extinction ratios of greater than 30 dB for both TE-pass and TM-pass polarizers.

Waveguide polarizers with hydrogenated amorphous silicon claddings.

We have fabricated TE- and TM-pass waveguide polarizers with polarization isolations of 42 and 35 dB, respectively. The devices were fabricated by the growth of hydrogenated amorphous silicon claddings on K(+)-Na(+) ionexchanged channel waveguides in glass. Cladding thicknesses were accurately tuned to permit optimum coupling of either a TE or a TM mode to the cladding. We have also demonstrated that a waveguide polarizer attenuation as high as 760 dB/cm can be measured by using a photothermal deflection technique.

Hepatitis B in a hospital for the mentally subnormal in South Wales.

The resident population in a long-stay hospital for the mentally handicapped was surveyed in order to assess evidence for past and present infection with the Hepatitis B virus. The authors found a 0.5% prevalence of carriage of Hepatitis Be Antigen and do not recommend mass vaccination of staff and residents in this hospital.