George H. Sigel

Pr 3+ -doped fluoride fiber amplifier operating at 1.31 μm

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.

Pr3+-doped GeGaS glasses for 1.3 μm optical fiber amplifiers☆

The synthesis and optical properties of Pr-doped GeGaS glasses are reported. The radiative properties associated with the important 1G4 → 3H5 transition of Pr3+ at 1.3 μm have been determined by absorption and fluorescence measurements coupled with Judd-Ofelt analysis. As compared with ZBLAN glass, Pr-doped GeGaS glasses have a longer fluorescence lifetime and a larger stimulated emission cross-section, which are favorable for an efficient fiber amplifier. The concentration quenching of Pr3+ in these glasses has also been studied by fluorescence lifetime measurements.

Spectroscopy of Dy 3+ in Ge–Ga–S glass and its suitability for 1.3-μm 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.

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.

Pr3+-DOPED FLUORIDE FIBER AMPLIFIER OPERATING AT 1.31 µm

The authors propose a new Pr3+-doped fluoride fiber amplifier operating around 1.3 μm and demonstrate an effective amplification of 5.2 dB at 1.31 μm for the first time.

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.

Optical characterization of Pr3+ and Dy3+ doped chalcogenide glasses

Abstract The optical properties of several sulfur-based glasses doped with Pr3+ and Dy3+ have been measured, with emphasis on the 1.3 μm emission quantum efficiency. Glass hosts prepared using conventional methods include As2S3, As2S3 with 1.7 mol% I2, Ge30As10S60, Ge25Ga5S70, and Ge35S56.5I8.5 for Pr3+, and all but the As2S3 based compositions for Dy3+. Data obtained from optical absorption and fluorescence spectra and fluorescence lifetime measurements were used for theoretical predictions of quantum efficiency. These theoretical efficiencies were compared to absolute efficiency measurements using either an integrating sphere based system or a self-calibration technique (Pr3+ only, no As2S3-based glasses). The latter method produced erroneous values for glasses having electronic absorption edges beyond 500 nm, possibly due to a host sensitization phenomenon. A 100 ppm Pr2S3 doped GeGaS glass was the most efficient at 1.3 μm, measuring 93% via the integrating sphere technique. The measured efficiencies for Dy3+ doped glasses at 1.3 μm, the first reported to our knowledge, were less than those theoretically predicted. The most efficient Dy3+ doped sample, a 0.1 wt% Dy2S3 doped GeSI glass, was measured to be 6%.

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.

Spectroscopic evaluation of Yb/sup 3+/-doped glasses for optical refrigeration

The absorption and emission properties of Yb/sup 3+/-doped ZBLANP, BIGaZYT and QX/Yb phosphate glasses are studied to evaluate their potential for laser-induced fluorescent cooling or optical refrigeration. The efficiency of optical refrigeration increases with pump wavelength in the anti-Stokes region. The cooling efficiencies of the three glasses as a function of temperature are evaluated at the wavelength /spl lambda/p corresponding to the absorption coefficient of 10/sup -3/ cm/sup -1/. For temperatures <110 K, the cooling efficiency of the BIGaZYT glass may be more than twice that of the ZBLANP.

1.47, 1.88 and 2.8 μm emissions of Tm3+ and Tm3+-Ho3+-codoped tellurite glasses

Abstract Tellurite glass is a good host for Tm 3+ because of high quantum efficiency and good glass stability. For 1.47 μm the upper limit for Tm 2 O 3 concentration without quenching is 0.4 wt%. For 1.88 μm, it should be 0.4 wt% in order to take advantage of the two-for-one transition.