Concentration and Distribution of E R , A L and P in Silica-Based Optical Fiber Preforms by Sims

  • PDF / 301,552 Bytes
  • 6 Pages / 414.72 x 648 pts Page_size
  • 18 Downloads / 199 Views

DOWNLOAD

REPORT


CONCENTRATION AND DISTRIBUTION OF ER, AL AND P IN SILICA-BASED OPTICAL FIBER PREFORMS BY SIMS D.W. OBLAS, T.WEI, W.J. MINISCALCO AND B.T. HALL GTE Laboratories Inc., 40 Sylvan Road, Waltham, MA 02254 ABSTRACT Secondary ion mass spectrometry (SIMS) was used to measure the Er, Al and P distributions across (perpendicular to) and along (parallel to) the axis of Er3+-doped silica based preforms and fibers prepared by a solution doping technique. Specially prepared low-melting silicate glass standards containing known concentrations of Er were used to calibrate the spectrometer to obtain a semi-quantitative measurement of the Er concentration. It was found that the Er concentration can vary along a 4-cm section of the preform by as much as a factor of two. The Al concentration also changed along the length of the preform, but to a smaller degree. Finally, instrumental limitations for measuring the Er, Al and P distributions in the optical fiber samples were determined. INTRODUCTION Rare earth doped optical fibers are now being widely investigated for their use as lasers and amplifiers [1,2]. In particular, silica-based Er3+-doped fibers have been demonstrated as a potentially high-gain, low-cost optical amplifier for telecommunication applications. In order to refine the fabrication process and to optimize device performance, it is informative to determine the concentrations and the distribution of dopants (perpendicular to) and along (parallel to) the axis of the preform as functions of process parameters and the optical properties of the fiber. In addition, it is interesting to note the relative spatial distribution of the respective constituents comprising the core since optical performance of the fiber will depend on the relative distribution of the dopants. Several analytical methods have been used in determining the profiles and the concentrations of rare earth species in optical fiber matrices [3,4]. For example, the electron microprobe analyzer offers a straightforward method for determining rare earth dopants in the high concentration range with a spatial resolution of the order of 1 g~m [5]. However, for concentrations in the several hundred ppm range, there are only a limited number of techniques readily available. Secondary ion mass spectrometry is probably the most useful and has been used in recent studies [6). Since the relative (elemental) sensitivities vary over a wide range, quantitation is extremely difficult [7]. There are also matrix and instrumental effects as well. Therefore, unless some form of appropriate standard is employed, quantitation is impossible. In addition, there is further complication in collecting quantitative data by SIMS since the samples being investigated here are insulators [8]. EXPERIMENTAL Samples

The rare-earth ions were incorporated by the solution doping technique [9]. The preforms were prepared by first depositing a silica barrier layer on the inside surface of a silica tube using the modified chemical vapor deposition (MCVD) method. A porous silica layer was subsequentl

Data Loading...