Single mode fibers for the Faraday effect current sensor have been developed with extremely small stress-optic coefficient glass for core. The properties of the fiber and the characteristics of the sensor system constructed with the fiber exhibited the usefulness of the fiber for current sensor.
The basic system of the optical fiber-type Faraday effect current sensor for electric power apparatus has been developed. According to the experiments, it became clear that the developed system showed excellent polarization characteristics and small tempereture dependence. Though the vibration dependent fluctuation of the output is observed, a remedy is suggested.
Diode..pumped cw laser oscillations in 2.7gi region were obtained using lOmol% ErF3 doped fluorozircoaluminate glass fibers. Lasing threshold proportionately decreased with decreasing fiber core diameter. Minimum threshold observed for 1 lOji core fiber was approximately 10mW in absorbed pump power. Maximum slope efficiency of 8% was obtained for 1% output coupling. Output performance was significantly affected by the pump wavelength. Mechanism ofcw lasing in this "selftenninating" system was discussed.
. INTRODUCTIONThe recent developments of 2.7p lasers are quite attractive for the medical and sensor applications. The transition of4!1112 -4Iy ofEr3 ion is favorably employed for the laser emission in the region of 2.7-2.9j.t. This transition is "self-terminating", that is, the upper level life time is shorter than the lower level one. It has been reported for ECYAG and ErYLF crystals that higher Er3 doping was preferable for the laser oscillation. Recently several works on diode-pumped cw laser using ECYLF crystal 1 and Er:fluorozirconate glass bers2 have been reported. However, fluorozirconate glass fibers are neither chemically stable nor mechanically strong. We have developed fluorozircoaluminate glasses which are superior than fluorozirconate glasses in terms of chemical and mechanical properties and have reported a diode-pumped cw laser oscillation 4. In this paper, optimization ofglass composition, laser performances ofEr3 doped fluorozircoaluminate (AZF) glass fibers as well as excitation mechanism of cw lasing are discussed.
.EXPERIMENTSVarious infra-red transmitting glasses doped with Er3 ion were prepared. However, only fluoride, fluorophosphate and tellurite glasses were selected for the evaluation since the others had some difficulties such as high melting temperature, strong crystallization tendency and so on in order to obtain good quality glasses. Glass compositions evaluated in terms of2.7i emission efficiency were listed in Table 1 . Fluoride glasses were prepared by melting the batch materials in glassy carbon crucibles in a reactive gas atmosphere inside a glove box. Highly pure fluorides were employed for the batch materials to eliminate the contamination by impurities. The melt in the crucible was rapidly cooled to the glass transition temperature and annealed. Fluorophosphate and tellurite glasses were melted in platinum or gold crucibles in dry nitrogen or dry oxygen atmosphere and poured into graphite moulds followed by annealing. Samples for the optical property measurements were fabricated to the size of 25x10x4mm3 of which four surfaces were optically polished. 386 / SPIE Vol. 1513 Glasses for Optoelectronics 11(1991) O-8194-0622-8/91/$4.OO Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/15/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
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