OFC ’98 Technical Digest Wednesday Afternoon 0 141

6Hl l/2

6H,3/2

PDFF at the input signal power of -3 dBm. The output power of PDFF changes from 14.1 dBm to 9.8 dBm over the 1290-1330-nm wavelength region in a bi-directional pumping configuration, where the input signal power and the pump power were -3 dBm and 190 mW, respectively. On the other hand, the hybrid PDFF/PDCF exhibits less variation of 2 dB in the output power, exceeding 11 dBm over the same wavelength region. Higher output power with flattened output spectrum is expected by using a PDCF with lower background loss.

We have proposed a novel configuration of PDFA, which realizes a flat output spectrum and higher output power in the 1290-1330-nm wavelength region. 1. E. Ishikawa etal., in OpticalAmplifiers and theirApplications, Vol. V,

OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 1996), pp. 36-38. H. Tawarayama et al., in Optical Amplifiers and their Applications, Vol. XVI, OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 1997), paper PD1.

2.

1.3 pm

WG8 3:15pm

Dy-doped selenide glass for 1.3-pm optical fiber amplifiers

L.B. Shaw, B.J. Cole, J.S. Sanghera, I.D. Aggarwal, D.T. Schaafsma,* Code 5606, U.S. Naval Research Laboratory, Washington, D.C. 20375

Dy3+-doped materials have been proposed for optical amplifiers at 1.3 pm. Dy3+ has several advantages over Pr3+-based amplifiers for 1.3-ym telecommunication applications. First, as seen in Fig. 1, numerous pump bands exist in the near-IR for populating the (6H,,,, 6Fl level. Second, these pump bands have absorption coefficients > l o times that of the Pr3+ ‘G, level in the same host. Third, the emission cross section of the (6H,/,, 6F,,,,) level is in general greater than the Pr3+ ‘G, level in the same host.’ These factors promise much shorter device lengths and better performance than is possible for Pr3+-doped materials. This, in turn, relaxes the tolerances on fiber

%/2

%/2

6H7,2 tF9/2 4 1.1 pm

WG8 Fig. 1. Energy level diagram of Df+.

o.8 GeAsSe based glaiss h

k O.’ 0.6

0 0.5

$ 0.4

9 0.3

E

0.2 $ I \ I / \

0.1 e

1000 1100 1200 1300 1400 1500

‘Wavelength (nm)

WG8 Fig. 2. GeAsSe-based glass.

Room-temperature absorption and emission spectra of Dy in a

background loss, which is a key roadblock in the development of Pr3+-doped fiber amplifiers.

Host materials suggested have included sulfide-based chalco- genide glass’-3 and LaC1, crystalline material.4 Sulfide glass materials show promise as hosts for the Dy3+ ion. The quantum efficiency of Dy3+ in GLS glass, for example, is 29% with a UT product of 220 X lopz6 cmz 5.’ However, this material is expected to suffer bottleneck- ing and subsequent ESA, which would degrade amplifier perfor- mance. LaCl,, while possessing good spectroscopic properties, is a hygroscopic crystalline material. Fabrication of this material into waveguides and protection of the waveguides from moisture would be technologically challenging.

A material that overcomes many of the limitations imposed by sulfide glass and chloride crystalline materials is a glass based on a modified GeAsSe composition. Dy3+ was doped into the GeAsSe- based composition at up to 1500 ppm. Absorption and emission spectra are shown in Fig. 2. The absorption spectra shows strong features at 1.1 p m and 1.3 p m suitable for populating the (6H,/2, 6Fll,z) level. Peak of the (6H912, 6F,,,z) emission occurs at 1.33 pm. The measured excited-state lifetime in these glasses is 300 ps. Judd- Ofelt calculations show a radiative rate of 320 ps for the coupled (6H,,z, 6F,,/2) level and a branching ratio of 90% for the 1.3-pm transition. Using the measured lifetime and Judd-Ofelt radiative rate, a radiative quantum efficiency of 90% was calculated for the (6H,/2, 6Fl,,2) level. Such a large radiative quantum efficiency and branching ratio should reduce the amount of bottlenecking and ESA, which would occur in 1.3-km amplifier operation. The emission cross sec- tion, u, of the 1.3-pm transition was found to be 2.7 X lo-” cm, resulting in a UT value of 810 X

Core-only doped fibers of 200-ym diameter have been drawn from this composition with losses of 2 dB/m near 1.3 pm. Work is currently being performed on fabrication of core-clad fiber. Details of this work will be delivered at the meeting. *University Research Foundation, Greenbelt, Maryland 20770 1.

2.

3.

4.

cm2 s.

S. Tanabe, T. Hanada, M. Watanabe, T. Hayashi, N. Soga, J. Am. Ceram. SOC. 78,2917-2922 (1995). D.W. Hewak, B.N. Samson, J.A. Medeiros Neto, R.I. Laming, D.N. Payne, Electron. Lett. 30,968-969 (1994). D.P. Machewirth, K. Wei, V. Krasteva, R. Datta, E. Snitzer, G.H. Sigel Jr., J. Non-Cryst. Solids 213,214,295-303 (1997). R. Page, K. Schaffers, S. Payne, W. Krupke, IEEE J. Lightwave Technol. 15,786-793 (1997).