Spectroscopy of Dy(3+) in Ge-Ga-S glass and its suitability for 1.3-microm fiber-optical amplifier applications.

Absorption and emission spectra, along with lifetime measurements, of Dy(3+) in Ge-Ga-S glasses are reported. Fluorescence is observed at 1.3, 1.8, and 2.9 microm. A Judd-Ofelt analysis is performed to determine branching ratios and quantum efficiencies. The hypersensitive transition (6)F(11/2) ? (6)H(15/2) at 1.3 microm has a quantum efficiency of 17%. Its suitability for an optical amplifier at 1.3 microm depends on the excited-state absorption from the (6)H(11/2) and (6)H(13/2) states, which has not yet been measured.

Optical properties of AlF(3)-based glasses doped with Pr(3+), Yb(3+) and Lu(3+).

Rare-earth ions can easily be incorporated into fluoride glasses in moderate to large concentrations. Because these glasses possess low fundamental frequencies, they appear to have many advantages over oxide glasses as hosts for rare-earth ions used in optical amplifiers and lasers. We have investigated the optical properties (fluorescence, absorption, and excited-state lifetimes) of AlF(3)-based glass doped with Pr(3+), Yb(3+) and Lu(3+). The effects of different dopant levels on the optical properties of this glass system have also been investigated. These results are compared to those obtained for the same ions in other glass hosts.

Excimer-laser-induced spatially variant luminescence in pure-silica core fibers with fluorine-doped silica cladding.

Optical fibers with pure silica cores of both low and high water content and fluorine-doped silica claddings were irradiated with 248 nm (KrF) excimer-laser radiation. In addition to the differences in the spectra of luminescent emissions of the respective cores, spatial variance was observed in the luminescence behavior across cross sections of the cores. Photographic evidence of this phenomenon is presented along with the corresponding luminescence spectra. Spectral correlations of the spatial variances are made, and the defects that are responsible for the luminescence are discussed.

Development of a porous polymer pH optrode.

A novel fiber-optic pH sensor has been developed with long-term stability and high sensitivity. The sensor is based on a porous cellulose triacetate fiber immobilized with Congo Red (pH indicator). This intrinsic fiberoptic pH sensor has shown excellent sensitivity, reversibility, and stability. It has also been demonstrated that the pH optrode is immune to metal-ion interferences.

Attenuation of incoherent infrared radiation in hollow sapphire and silica waveguides.

The attenuation of incoherent infrared radiation for wavelengths from 6 to 20 microm was investigated for hollow sapphire and silica waveguides suitable for applications in spectroscopy and thermometry. A low-attenuation region was exhibited between 9.6 and 17.2 microm for hollow sapphire fibers and between 7.25 and 9.5 microm for hollow silica fibers as a result of the cladding index of refraction dipping below that of the air core (n approximately 1). Losses have been characterized as a function of fiber diameter, launch conditions, and waveguide bend radius for cladding regions of both n > 1 and n < 1. In addition, the remote infrared sensing capability of the hollow waveguides was demonstrated by the detection of CO(2) in N(2) by utilizing hollow sapphire fibers capped with ZnSe windows.

Remote infrared chemical sensing using highly durable AlF(3)-based glass fibers.

Unclad, low-loss AlF(3)-based glass fibers with enhanced chemical durability have been successfully used for the first time to our knowledge as intrinsic evanescent infrared sensors for monitoring liquid chemicals. Different liquids with absorption bands between 1 and 4.5 microm, such as alcohol, acetonitrile, and mixtures of alcohol/acetonitrile and water/acetonitrile, have been tested. These fibers have also been used successfully as distributed sensors for simultaneous monitoring of different chemical species.

Pr(3+)-doped fluoride fiber amplifier operating at 1.31 microm.

We propose what is to our knowledge the first use of a Pr(3+)-doped fluoride fiber amplifier as a practical amplifier operating at the 1.3-microm band, based on a demonstration of signal amplification and a spectroscopic investigation. The feasibility of the fluoride fiber amplifier is confirmed.

Remote fiber-optic chemical sensing using evanescent-wave interactions in chalcogenide glass fibers.

An infrared-transmitting chalcogenide fiber was used as an optical probe to analyze qualitatively and quantitatively various chemical substances in aqueous solutions. An unclad fiber with 380-microm diameter was combined with a Fourier transform infrared spectrometer to monitor the concentration of the analytes in solutions by measuring the changes in the absorbance of their fundamental vibration peaks. A linear relationship was observed between the absorption by the vanescent field and concentrations of various analytes. For this study low concentrations of acetone, ethyl alcohol, and sulfuric acid were detected in aqueous solutions. The minimum detection limit for these three chemical substances was 5, 3, and 2 vol. %, respectively, with a sensor length of 15 cm. It was also demonstrated that the same sensor design is capable of monitoring gaseous species such as dichlorodifluoromethane.

Porous plastic optical fiber sensor for ammonia measurement.

A porous plastic optical fiber has been developed for use in chemical gas sensing. This porous plastic waveguide, which was made with copolymer materials, has an interconnective porous structure as well as uniformity of pore size. These sensors are based on in-line optical absorption within the porous plastic fiber core and have much greater sensitivities than sensors based on evanescent coupling to a surrounding medium. Furthermore, this fiber simultaneously exhibits very high gas permeability and liquid impermeability. This combination makes the fiber particularly suitable for gas concentration measurements in aqueous samples. An ammonia gas sensor has been tested to demonstrate the effectiveness of this porous plastic waveguide.

Porous optical fibers for high-sensitivity ammonia-vapor sensors.

A new porous glass optical fiber has been developed for use as a sensor for the detection of ammonia vapors at low concentrations. The porous structure that remains after selective heat treatment, phase separation, and chemical leaching of a borosilicate glass imparts a high surface area to the fiber core. Ammonia vapors permeating into the porous zone, which is pretreated with a reversible pH dye indicator, produce a spectral change in transmission. The resulting pH change is measured by in-line optical absorbance and is proportional to the ambient-ammonia concentration. Ammonia-vapor concentrations as low as 0.7 part in 10(6) have been detected.

Detection scheme in a fiber-optic magnetic-field sensor free from ambiguity due to material magnetic hysteresis.

A new technique has been demonstrated in the detection of low-frequency or dc magnetic fields in an optical-fiber interferometric sensor using the magnetostrictive approach. This technique permits magnetic-field measurements free of ambiguity associated with hysteresis effects of the material.

Characteristics of fiber-optic magnetic-field sensors employing metallic glasses.

A variety of extremely high-sensitivity, room-temperature magnetic-field sensors have been fabricated and tested using single-mode fibers in conjunction with highly magnetostrictive metallic glasses. Minimum detectable fields of 5 x 10(-9) Oe/m fiber are reported. The typical characteristics of the fiber magnetometers are summarized.