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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 20 — Sep. 27, 2010
  • pp: 20661–20666
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Evidence of two erbium sites in standard aluminosilicate glass for EDFA

R. Peretti, A.M. Jurdyc, B. Jacquier, E. Burov, and A. Pastouret  »View Author Affiliations


Optics Express, Vol. 18, Issue 20, pp. 20661-20666 (2010)
http://dx.doi.org/10.1364/OE.18.020661


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Abstract

Site distributions of Er3+-doped aluminosilicate preforms of standard EDFA were studied by the low temperature Resonant Fluorescence Line Narrowing (RFLN) spectroscopy. Two erbium concentration samples with the same glass base were investigated. At very low erbium concentration, two classes of sites were identified, related to the number of AlO6 octahedral linked by two oxygen edge-sharing to Er3+ in the coordination sphere. As erbium concentration is increased, the high AlO6 coordinated class of sites is smeared out by the optical response of the one AlO6 coordinated class of sites.

© 2010 OSA

Introduction

During the two decades since the demonstration of the first Erbium Doped Fiber Amplifier (EDFA) [1

1. R. Mears, L. Reekie, J. Jauncey, and D. N. Payne, “High-gain rare-earth rare-earth-doped fiber amplifier at 1.54µm,” in Proceedings OFC, Reno, Nevada (1987)

], this technology has experienced exponential growth in the commercial market. Moreover, the usage of WDM has increased the need for continued improvement of the optical properties of the glass based amplifiers. Moreover the introduction of Wavelength Division Multiplexing (WDM) into the system increased this need because of wide gain band demand. The strong correlation between the spectral gain bandwidth and the erbium spectroscopic data, such as emission and absorption cross sections and excited state lifetime, makes these parameters the key elements to explore in looking for improved materials. As seen so far, these parameters are predetermined by the Er3+ local environment in the glass, i.e. over few nanometers distance scales.

To improve the spectral gain bandwidth of the EDFA, many studies have investigated new glass chemical compositions; The goal being to modify the local crystal field environment around the erbium ions to affect the Stark energy level and the homogeneous and inhomogeneous linewidths . The linewidth change in different local crystal field is only 1 or 2 nanometers with respect to the standard value of 31nm in aluminosilicate host. This is one of the reasons that we focus our attention to a deeper investigation of the inhomogeneous broadening of the standard aluminosilica glass composition with the idea to better describe the local environment of erbium ions. Small differences in the gain performance of different aluminosilica glass fibres have been detected that may arise from the small change of local crystal field seen by the dopant in the disordered glass. On the other hand, the understanding of the erbium localization as well as the knowledge of the glass structure itself may allow finding alternate chemical or physical route to achieve the desired optical properties. In that sense, nanoscale engineering of the material may be a promising route for future active materials [6

6. W. Blanc, B. Dussardier, G. Monnom, R. Peretti, A.-M. Jurdyc, B. Jacquier, M. Foret, and A. Roberts, “Erbium emission properties in nanostructured fibers,” Appl. Opt. 48(31), G119–G124 (2009), http://ao.osa.org/abstract.cfm?URI=ao-48-31-G119. [CrossRef] [PubMed]

].

In this letter, we report the Resonant Fluorescence Line Narrowing (RFLN) study of two low erbium-doped optical preforms of standard EDFA where we have been able to detect two sites erbium distributions depending upon erbium concentration. Before describing the new experimental results, we recall that codoping germanosilica glass with alumina enhances erbium solubility in the glass network while it shifts the main erbium fluorescence peak towards high energy and broadens the spectrum at room temperature [7

7. B. Ainslie, “A review of the fabrication and properties of erbium-doped fibers for optical amplifiers,” J. Lightwave Technol. 9(2), 220–227 (1991). [CrossRef]

]. Moreover this shift has been studied in great details in aluminosilicate glass perform indicating a strong sensitivity on alumina contents below 2 w% as shown in Fig. 1
Fig. 1 Fluorescence peak position as a function of Aluminum concentration for different samples [8]
[8

8. L. Bigot, B. Pierre, B. Manardo, A.-M. Jurdyc, and B. Jacquier, “Etude de l'influence des codopants sur le profil de fluorescence de l'erbium à 1.5µm,” internal report LPCML (2000).

].

Experiments

Two cylindrical preform samples have been fabricated by DRAKA company, using the Modified Chemical Vapor Deposition (MCVD) technique [9

9. M. J. F. Digonnet, M. K. Davis, and R. H. Pantell, “Rate Equations for Clusters in Rare Earth-Doped Fibers,” Opt. Fiber Technol. 1(1), 48–58 (1994), http://www.sciencedirect.com/science/article/B6WP0-45SJ8JV-5/2/b4c0d012faba1bda3c0529cdd3e655a5. [CrossRef]

]. The host material is the same SiO2 matrix with the usual doping weight concentrations of few percent of Al oxide (less than 2 w%) and less than a percent of other dopant like Geoxide. The difference between these two samples is the Er3+ content. Sample A experiences a 4dB/m fibre losses at 1,53µm, approximately 250 ppm weight doped Er3,+ contrary to 12dB/m for sample B (~1000 ppm weight) at the same wavelength. Notice that the usual erbium concentration in standard EDFA is around 400 ppm weight. Both samples have the same geometry: the core size is around 2 mm diameter and 5 mm length embedded in a 1 cm diameter cladding. Samples were carefully polished with good optical quality before experiments. Room temperature fluorescence measurements show an identical spectral profile and no further evidence of inhomogeneity.

Results

The electronic transition under investigation by RFLN is between the lowest energy level of the fundamental 4I15/2 level and the lowest energy level of the exited state 4I13/2; notice that at 1.5K, the experimental conditions, the population of the energy sublevel of the manifolds other the ground level is negligible. Figure 2
Fig. 2 IDS spectrum of Er3+ in sample A at 1,5K by RFLN. Experiments: solid black lines depict RFLN response (spectral resolution limited) and black squares, the energy of each RFLN spectrum. Fitting: grey solid line reproduces a bi-Gaussian fit and dashed and dotted black lines, the composition of the bi-Gaussian fit.
shows the IDS from RFLN at 1.5K for sample A. Black lines represent RFLN line profile limited by the spectral response function of our monochromator. Black squares are the energy of these lines; they represent IDS of Er3+ emission in the sample. This IDS was fit by a bi-Gaussian profile in gray line, with the two Gaussian components, respectively in dotted and dashed lines.

Figure 3
Fig. 3 IDS spectrum of Er3+ in sample B at 1,5K by RFLN. Solid black lines depict RFLN spectra (spectral resolution limited) and black squares, the energy of each RFLN peak. The grey solid line represents the Gaussian fit.
reports the result of sample B with the identical experimental conditions. Black lines represent RFLN lines. Black squares are the peak energy of these lines; they represent IDS of Er3+ emission in the sample. To the contrary of sample A only one Gaussian profile is needed to reproduce the experimental linewidth, in gray line.

As stated previously the RFLN profiles are limited by the resolution of our monochromator and the strength of the signal which is seen by RFLN narrower lines for sample B than for sample A because of higher Er3+ doping and then better resolution. We check that all the profiles were independent of pump power and all the spectra reported are for the lowest power with a reasonable signal/noise ratio.

Table 1

Table 1. Parameters with experimental error bars of the Gaussian curves used to fit IDS data of samples A and B. Furthermore proportion of the two Gaussian bands to the full profile is indicated as weight parameter based on area measurements.

table-icon
View This Table
gives all the parameters used to fit the IDS of the both samples (when IDS curves are normalized to the maximum) and for A sample, we calculate the proportion of the two Gaussian components with respect to the surface area.

We see in Fig. 3 that the IDS is quite symmetrical and looks consistent with a Gaussian shape. Actually, only one Gaussian fits really well these data. On the other hand, the data of IDS reported on Fig. 2 are not symmetrical, and more than one Gaussian was needed to reproduce it. A bi-Gaussian profile was clearly adequate. Gaussian profiles were chosen because Gaussian distribution of Er3+ transition depicts the statistical distribution of one local environment for Er3+ in the matrix. If there is more than one Gaussian in these fits, there is more than classe of sites (as described in the following) . In the followings, we discuss what means this change of local environment.

Discussion

In a glass, the disorder makes the interatomic distances and angles between ions of silica network different from one specific Er3+ environment to another. There is generally a statistical distribution of environment for which the optical transition energies have a mean value and a broadening that justifies a fit of the RFLN spectra with Gaussian profiles. In that respect such distribution is called “a class of sites”. In the results reported above, it is clearly shown that there are two classes of sites which differ by their mean transition energy and by the width of their distribution in sample A. On the contrary, in sample B there is only one class of sites. Comparing the two Gaussian’s area in sample A, we can say that the occurrence of the high energy class of sites is very low. That is why we call as “minority class of sites” (mCS) the high energy distribution and “majority class of sites” (MCS) the low energy distribution. We have observed that the mCS is no more visible with increasing erbium concentration (sample B). So, we assume that the number of sites in the mCS is limited but that the filling probability of the sites is higher. We believe that these features are the signature of the existence of two different erbium environments with a more ionic character for the high energy distribution in agreement with nephelauxetic effect and optical basicity [10

10. A. Tesar, J. Campbell, M. Weber, C. Weinzapfel, Y. Lin, H. Meissner, and H. Toratani, “Optical properties and laser parameters of Nd3+-doped fluoride glasses,” Opt. Mater. 1(3), 217–234 (1992), http://www.sciencedirect.com/science/article/B6TXP-46JYH7T-12/2/ebb604aa56cedf44ce25f8ad7c54286b. [CrossRef]

12

12. P. Linus, The Nature of Chemical Bond (Cornell University Press, 1989).

]. In literature, the observation of 2 sites for other rare earth in similar glass was already reported in Eu3+-doped aluminosilicate glass [13

13. M. Nogami, T. Nagakura, and T. Hayakawa, “Site-dependent fluorescence and hole-burning spectra of Eu3+-doped Al2O3-SiO2 glasses,” J. Lumin. 86(2), 117–123 (2000), http://www.sciencedirect.com/science/article/B6TJH-3YJYG4V-5/2/2c0b7e6bdc228c1b81f4d829a6cecc38. [CrossRef]

] and, in Er3+-doped fluoride glasses [14

14. A. M. Jurdyc ans S. Guy, “Deux sites à faibles concentrations pour différents verres de fluorures,” internal report LPCML (2004).

,15

15. S. Guy, L. Bigot, I. Vasilief, B. Jacquier, B. Boulard, and Y. Gao, “Two crystallographic sites in erbium-doped fluoride glass by frequency-resolved and site-selective spectroscopies,” J. Non-Cryst. Solids 336(3), 165–172 (2004), http://www.sciencedirect.com/science/article/B6TXM-4C0TKXW-2/2/ccff61d3d6adc78710cad5db05b2653a. [CrossRef]

] but always at low rare earth concentration

Conclusion

In this report, we pointed out the existence of two classes of sites in the standard telecom erbium-doped glass for EDFA. These two classes of sites are observed only at low erbium concentration and high alumina content. The number of AlO6 polyhedrons linked to Er3+ ions in the coordination sphere is suggesting the possible explanation of our observations in close agreement to what reported earlier for Eu3+ aluminosilicate glass [13

13. M. Nogami, T. Nagakura, and T. Hayakawa, “Site-dependent fluorescence and hole-burning spectra of Eu3+-doped Al2O3-SiO2 glasses,” J. Lumin. 86(2), 117–123 (2000), http://www.sciencedirect.com/science/article/B6TJH-3YJYG4V-5/2/2c0b7e6bdc228c1b81f4d829a6cecc38. [CrossRef]

]. However, in our case the high energy “sites” is attributed to the erbium environment for which more than one AlO6 is involved and it smeared out with increasing the erbium concentration. At room temperature, it is generally not clear if this behaviour plays a role in the performances of EDFA but controlling and engineering the erbium environment at the nanometric scale would be very useful to understand and improve the performances of EDFA.

Acknowledgement

The authors are grateful to the reviewers for the help to improve the manuscript.

References and links

1.

R. Mears, L. Reekie, J. Jauncey, and D. N. Payne, “High-gain rare-earth rare-earth-doped fiber amplifier at 1.54µm,” in Proceedings OFC, Reno, Nevada (1987)

2.

L. Bigot, A.-M. Jurdyc, B. Jacquier, L. Gasca, and D. Bayart, “Resonant fluorescence line narrowing measurements in erbium-doped glasses for optical amplifiers,” Phys. Rev. B 66(21), 214204 (2002), http://link.aps.org/abstract/PRB/v66/e214204. [CrossRef]

3.

M. Yadlowsky, and L. Button, “Pump-mediated inhomogeneous effects in EDFAs and their impact ongain spectral modeling,” Optical Fiber Communication Conference and Exhibit, 1998. OFC '98, Technical Digest -, 35–36 (1998). http://www.opticsinfobase.org/abstract.cfm?URI=OFC-1998-TuG5

4.

E. Desurvire, J. Sulhoff, J. Zyskind, and J. Simpson, “Study of spectral dependence of gain saturation and effect of inhomogeneous broadening in Erbium-doped aluminosilicate fiber amplifiers,” IEEE Photon. Technol. Lett. 2(9), 653–655 (1990). [CrossRef]

5.

R. Peretti, A. Jurdyc, B. Jacquier, E. Burov, and L. Gasca, “Resonant fluorescence line narrowing and gain spectral hole burning in erbium-doped fiber amplifier,” J. Lumin. 128(5–6), 1010–1012 (2008), http://www.sciencedirect.com/science/article/B6TJH-4R9GH1F-1/2/07dbf3f916f8a8d628aba9d36d9252f2.

6.

W. Blanc, B. Dussardier, G. Monnom, R. Peretti, A.-M. Jurdyc, B. Jacquier, M. Foret, and A. Roberts, “Erbium emission properties in nanostructured fibers,” Appl. Opt. 48(31), G119–G124 (2009), http://ao.osa.org/abstract.cfm?URI=ao-48-31-G119. [CrossRef] [PubMed]

7.

B. Ainslie, “A review of the fabrication and properties of erbium-doped fibers for optical amplifiers,” J. Lightwave Technol. 9(2), 220–227 (1991). [CrossRef]

8.

L. Bigot, B. Pierre, B. Manardo, A.-M. Jurdyc, and B. Jacquier, “Etude de l'influence des codopants sur le profil de fluorescence de l'erbium à 1.5µm,” internal report LPCML (2000).

9.

M. J. F. Digonnet, M. K. Davis, and R. H. Pantell, “Rate Equations for Clusters in Rare Earth-Doped Fibers,” Opt. Fiber Technol. 1(1), 48–58 (1994), http://www.sciencedirect.com/science/article/B6WP0-45SJ8JV-5/2/b4c0d012faba1bda3c0529cdd3e655a5. [CrossRef]

10.

A. Tesar, J. Campbell, M. Weber, C. Weinzapfel, Y. Lin, H. Meissner, and H. Toratani, “Optical properties and laser parameters of Nd3+-doped fluoride glasses,” Opt. Mater. 1(3), 217–234 (1992), http://www.sciencedirect.com/science/article/B6TXP-46JYH7T-12/2/ebb604aa56cedf44ce25f8ad7c54286b. [CrossRef]

11.

B. R. Reisfeld, and C. Jorgensen, Lasers and Excited States of Rare Earths (Springer-Verlag, 1977).

12.

P. Linus, The Nature of Chemical Bond (Cornell University Press, 1989).

13.

M. Nogami, T. Nagakura, and T. Hayakawa, “Site-dependent fluorescence and hole-burning spectra of Eu3+-doped Al2O3-SiO2 glasses,” J. Lumin. 86(2), 117–123 (2000), http://www.sciencedirect.com/science/article/B6TJH-3YJYG4V-5/2/2c0b7e6bdc228c1b81f4d829a6cecc38. [CrossRef]

14.

A. M. Jurdyc ans S. Guy, “Deux sites à faibles concentrations pour différents verres de fluorures,” internal report LPCML (2004).

15.

S. Guy, L. Bigot, I. Vasilief, B. Jacquier, B. Boulard, and Y. Gao, “Two crystallographic sites in erbium-doped fluoride glass by frequency-resolved and site-selective spectroscopies,” J. Non-Cryst. Solids 336(3), 165–172 (2004), http://www.sciencedirect.com/science/article/B6TXM-4C0TKXW-2/2/ccff61d3d6adc78710cad5db05b2653a. [CrossRef]

16.

A. Saitoh, S. Matsuishi, C. Se-Weon, J. Nishii, M. Oto, M. Hirano, and H. Hosono, “Elucidation of codoping effects on the solubility enhancement of Er3+ in SiO2 glass: striking difference between Al and P codoping,” J. Phys. Chem. B 110(15), 7617–7620 (2006), http://pubs.acs.org/doi/abs/10.1021/jp060702w. [CrossRef] [PubMed]

17.

A. Monteil, S. Chaussedent, G. Alombert-Goget, N. Gaumer, J. Obriot, S. Ribeiro, Y. Messaddeq, A. Chiasera, and M. Ferrari, “Clustering of rare earth in glasses, aluminum effect: experiments and modeling,” J. Non-Crystalline Solids 348, 44 – 50 (2004). Proceedings of the 6th Brazilian Symposium of Glases and Related Materials and 2nd International Symposium on Non-Crystalline Solids in Brazil, http://www.sciencedirect.com/science/article/B6TXM-4DNRW2C-1/2/a5cbba96ef8f1c59015780c5b635984f.

OCIS Codes
(060.2290) Fiber optics and optical communications : Fiber materials
(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
(300.2530) Spectroscopy : Fluorescence, laser-induced

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: June 21, 2010
Revised Manuscript: September 6, 2010
Manuscript Accepted: September 7, 2010
Published: September 15, 2010

Citation
R. Peretti, A.M. Jurdyc, B. Jacquier, E. Burov, and A. Pastouret, "Evidence of two erbium sites in standard aluminosilicate glass for EDFA," Opt. Express 18, 20661-20666 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-20-20661


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References

  1. R. Mears, L. Reekie, J. Jauncey, and D. N. Payne, “High-gain rare-earth rare-earth-doped fiber amplifier at 1.54µm,” in Proceedings OFC, Reno, Nevada (1987)
  2. L. Bigot, A.-M. Jurdyc, B. Jacquier, L. Gasca, and D. Bayart, “Resonant fluorescence line narrowing measurements in erbium-doped glasses for optical amplifiers,” Phys. Rev. B 66(21), 214204 (2002), http://link.aps.org/abstract/PRB/v66/e214204 . [CrossRef]
  3. M. Yadlowsky, and L. Button, “Pump-mediated inhomogeneous effects in EDFAs and their impact ongain spectral modeling,” Optical Fiber Communication Conference and Exhibit, 1998. OFC '98, Technical Digest -, 35–36 (1998). http://www.opticsinfobase.org/abstract.cfm?URI=OFC-1998-TuG5
  4. E. Desurvire, J. Sulhoff, J. Zyskind, and J. Simpson, “Study of spectral dependence of gain saturation and effect of inhomogeneous broadening in Erbium-doped aluminosilicate fiber amplifiers,” IEEE Photon. Technol. Lett. 2(9), 653–655 (1990). [CrossRef]
  5. R. Peretti, A. Jurdyc, B. Jacquier, E. Burov, and L. Gasca, “Resonant fluorescence line narrowing and gain spectral hole burning in erbium-doped fiber amplifier,” J. Lumin. 128(5–6), 1010–1012 (2008), http://www.sciencedirect.com/science/article/B6TJH-4R9GH1F-1/2/07dbf3f916f8a8d628aba9d36d9252f2 .
  6. W. Blanc, B. Dussardier, G. Monnom, R. Peretti, A.-M. Jurdyc, B. Jacquier, M. Foret, and A. Roberts, “Erbium emission properties in nanostructured fibers,” Appl. Opt. 48(31), G119–G124 (2009), http://ao.osa.org/abstract.cfm?URI=ao-48-31-G119 . [CrossRef] [PubMed]
  7. B. Ainslie, “A review of the fabrication and properties of erbium-doped fibers for optical amplifiers,” J. Lightwave Technol. 9(2), 220–227 (1991). [CrossRef]
  8. L. Bigot, B. Pierre, B. Manardo, A.-M. Jurdyc, and B. Jacquier, “Etude de l'influence des codopants sur le profil de fluorescence de l'erbium à 1.5µm,” internal report LPCML (2000).
  9. M. J. F. Digonnet, M. K. Davis, and R. H. Pantell, “Rate Equations for Clusters in Rare Earth-Doped Fibers,” Opt. Fiber Technol. 1(1), 48–58 (1994), http://www.sciencedirect.com/science/article/B6WP0-45SJ8JV-5/2/b4c0d012faba1bda3c0529cdd3e655a5 . [CrossRef]
  10. A. Tesar, J. Campbell, M. Weber, C. Weinzapfel, Y. Lin, H. Meissner, and H. Toratani, “Optical properties and laser parameters of Nd3+-doped fluoride glasses,” Opt. Mater. 1(3), 217–234 (1992), http://www.sciencedirect.com/science/article/B6TXP-46JYH7T-12/2/ebb604aa56cedf44ce25f8ad7c54286b . [CrossRef]
  11. B. R. Reisfeld, and C. Jorgensen, Lasers and Excited States of Rare Earths (Springer-Verlag, 1977).
  12. P. Linus, The Nature of Chemical Bond (Cornell University Press, 1989).
  13. M. Nogami, T. Nagakura, and T. Hayakawa, “Site-dependent fluorescence and hole-burning spectra of Eu3+-doped Al2O3-SiO2 glasses,” J. Lumin. 86(2), 117–123 (2000), http://www.sciencedirect.com/science/article/B6TJH-3YJYG4V-5/2/2c0b7e6bdc228c1b81f4d829a6cecc38 . [CrossRef]
  14. A. M. Jurdyc ans S. Guy, “Deux sites à faibles concentrations pour différents verres de fluorures,” internal report LPCML (2004).
  15. S. Guy, L. Bigot, I. Vasilief, B. Jacquier, B. Boulard, and Y. Gao, “Two crystallographic sites in erbium-doped fluoride glass by frequency-resolved and site-selective spectroscopies,” J. Non-Cryst. Solids 336(3), 165–172 (2004), http://www.sciencedirect.com/science/article/B6TXM-4C0TKXW-2/2/ccff61d3d6adc78710cad5db05b2653a . [CrossRef]
  16. A. Saitoh, S. Matsuishi, C. Se-Weon, J. Nishii, M. Oto, M. Hirano, and H. Hosono, “Elucidation of codoping effects on the solubility enhancement of Er3+ in SiO2 glass: striking difference between Al and P codoping,” J. Phys. Chem. B 110(15), 7617–7620 (2006), http://pubs.acs.org/doi/abs/10.1021/jp060702w . [CrossRef] [PubMed]
  17. A. Monteil, S. Chaussedent, G. Alombert-Goget, N. Gaumer, J. Obriot, S. Ribeiro, Y. Messaddeq, A. Chiasera, and M. Ferrari, “Clustering of rare earth in glasses, aluminum effect: experiments and modeling,” J. Non-Crystalline Solids 348, 44 – 50 (2004). Proceedings of the 6th Brazilian Symposium of Glases and Related Materials and 2nd International Symposium on Non-Crystalline Solids in Brazil, http://www.sciencedirect.com/science/article/B6TXM-4DNRW2C-1/2/a5cbba96ef8f1c59015780c5b635984f .

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