Er3+-doped phosphate glasses for fiber amplifiers with high gain per unit length

doi:10.1016/S0022-3093(99)00646-8

Journal of Non-Crystalline Solids

Volumes 263–264, 1 March 2000, Pages 364-368

https://doi.org/10.1016/S0022-3093(99)00646-8 Get rights and content

Abstract

The effect of the types of alkaline earth metal ions (Mg²⁺, Ca²⁺ and Ba²⁺) and concentration of Al₂O₃ and BaO on the refractive index and the effective emission linewidths of the ⁴I_13/2−⁴I_15/2 transition of Er³⁺ ions in phosphate glasses, 64P₂O₅ · 12Al₂O₃ · $3.5(Er_{2} O_{3} + La_{2} O_{3})·20.5 MO (M = Mg, Ca, Ba)$ and 64P₂O₅ · 3.5(Er₂O₃+La₂O₃) · (21.5 − x)Al₂O₃ · $(11+x) BaO (x=0,3.5,6.5 and 9.5)$ , were investigated. A single mode Er³⁺ doped phosphate glass fiber with a core diameter of 4 μm was fabricated by the rod-in-tube technique. A new Er³⁺ doped fiber amplifier is demonstrated pumping with a 980 nm fiber pigtailed-laser diode. A gain per unit length greater than 2 dB/cm is demonstrated, which is the largest gain per unit length for fiber amplifiers to our knowledge.

Introduction

Current typical Er³⁺-doped fiber amplifiers utilize approximately 20 m of silica fiber doped with approximately a few hundreds ppm (by weight) Er³⁺ ions [1]. A larger Er³⁺ doping concentration in silica glass results in concentration quenching caused by ion clusters [2]. An Er³⁺ doping concentration of greater than 2 wt% is required to decrease the length of the active fiber to a few centimeters for integrated devices. Phosphate and silicate glasses are superior to silica glass for larger erbium concentration doped optical amplifiers [3], [4], [5]. Many techniques including sol–gel [6], ion-exchanging [7] and RF sputtering [3] have been investigated for fabricating such large erbium concentration-doped planar waveguide amplifiers. Large erbium concentration-doped fibers were also investigated [8], [9]. Due to the phonon energy and solubility of rare-earth ions in phosphate glasses they are regarded as better hosts for Er³⁺ ions compared to silicate glasses [10]. Cooperative upconversion coefficient of ⁴I_13/2 level of Er³⁺ ions in phosphate glasses is smaller than that in silicate glasses [11].

This paper describes the effect of glass compositions on refractive indices and effective emission linewidths, the fabrication of single mode fiber and characterization of Er³⁺-doped phosphate glass fiber amplifiers.

Section snippets

Experiment

Compounds with less than 10 ppm of iron or of copper were used as the starting chemicals for glass preparation. The mixed chemicals were melted in an electric furnace using a quartz crucible at 1250°C. The liquid was then held at temperature for 30 min. After fusing, the glass liquid was transferred to a platinum crucible and the temperature was increased to 1350°C. Nitrogen gas was purged through the liquid to remove hydroxyl ions (OH⁻¹). The liquid was cast into an aluminum mold. Two series

Effect of glass composition on refractive index and effective linewidth

Fig. 1(a) shows that the refractive index of phosphate glass increased when the ionic radius of alkaline earth metal increased from Mg, to Ca, to Ba. Fig. 1(b) illustrates the effect of the concentration of BaO and Al₂O₃ on the refractive index of the samples. The refractive index increased when the concentration of BaO increased and the concentration of Al₂O₃ decreased.

We investigated the effect of glass compositions on the linewidth of the ⁴I_15/2−⁴I_13/2 transition of emission spectrum of

Effect of glass composition on refractive index and effective linewidth

The effect of composition on refractive index in phosphate glasses was reported in many papers [19], [20]. However, glass compositions of our fibers differed. Al₂O₃ contents reported in Refs. [19], [20] were less than in our fiber samples. We fabricated two series of samples to investigate the effect of glass compositions on refractive index since the refractive index is critical in the control of mode profile, which affect the performance of the optical fiber amplifier.

According to

Conclusions

The effective emission linewidth of the ⁴I_13/2−⁴I_15/2 transition of Er³⁺ ions can be modified by adjusting glass compositions. A gain per unit length, 2.1 dB/cm, was demonstrated from a single mode phosphate glass fiber doped with $3.8×10^{20} ions/cm^{3} Er^{3+}$ ions. A larger gain per unit length could be achieved by increasing pump power based upon our theoretical modeling. Results indicate that Er³⁺ doped phosphate glasses are promising materials for miniature fiber amplifiers.

Acknowledgements

The authors acknowledge the support from BMDO through the SBIR and the Center for Optoelectronic Devices, Interconnects and Packaging (COEDIP). K.S. is grateful to the Conseil Regional de Bretagne for financial support.

References (25)

S Jiang et al.
J. Non-Cryst. Solids
(1998)
M Shimizu et al.
IEEE Photonics Tech. Lett.
(1990)
R Quimby et al.
J. Appl. Phys.
(1994)
Y.C Yan et al.
App. Phys. Lett.
(1997)
J Shmulovich
SPIE
(1997)
K.A Winick
SPIE
(1998)
G.C Righini et al.
SPIE
(1998)
P Camy et al.
Electron. Lett.
(1996)
M.R.X de Barros et al.
IEEE Photonics Technol. Lett.
(1996)
T Nishi et al.
Jpn. J. Appl. Phys.
(1992)

T Ohtsuki et al.

J. Opt. Soc. Am. B

(1996)

W.J Miniscalco et al.

Opt. Lett.

(1991)

Cited by (262)

Insights on the structure and properties of sodium iron phosphate glasses from molecular dynamics simulations
2024, Journal of Nuclear Materials
Iron phosphate glasses are promising nuclear waste forms while more detailed understanding of their structures and structure-property relations are still needed to better design waste glass compositions. In this work we report studies of three series of sodium iron phosphate (NFP) glasses: 60P₂O₅-(40-x)Fe₂O₃-xNa₂O (x = 0→40), (100–2x)P₂O₅-xFe₂O₃-xNa₂O (x = 5→17.5) and one with different iron redox ratio, to understand the composition as well as the iron redox effects on the structure and properties of these glasses using molecular dynamics simulations with effective two-body and three-body potentials. Structural analyses, including pair distribution function, bond angle distribution, Q_n distribution, and polyhedral connectivity, were performed to obtain in-depth information on short-range and medium-range structural features. The P-O pair distributions showed a first peak splitting with phosphorus-bridging and non-bridging oxygen contributions. This and the average P-O and other cation-oxygen bond distances are in excellent agreement with experiments. The coordination number of P⁵⁺ remained four while that of Fe³⁺ increased from 4.30 to 4.72 with decreasing Fe/Na ratio. Polyhedral linkage analysis showed [PO₄] units linked with [PO₄] and [FeO_x] through corner-sharing while the [PO₄]-[FeO_x] linkages become dominant for compositions with Fe₂O₃ larger than 15 mol%. The effect of iron redox ratio on the structure of NFP glasses was also studied and it was found that bond lengths and coordination numbers were not strongly affected, while the reduction of iron introduced higher network distortions, as evident by O-P-O bond angle and Q_n distribution. The glass transition temperature (T_g) showed a monotonic increase with Fe₂O₃ in the first series, in good agreement with experiments, while those of the second series showed a maximum at P₂O₅ = 82 mol%. Calculated elastic moduli were found to increase with Fe₂O₃ in the first glass series, which was be explained by the increase of network connectivity, while those of the second series decrease with Fe₂O₃ due to decrease of P₂O₅.
Erbium doped gadolinium borate glasses for optical communication window applications
2023, Optik
The intent of the current work is to synthesize (79-x) B₂O₃ + 10ZnO+ 10BaO+ xGd₂O₃ + 1Er₂O₃ where (x = 0.0, 5.0, 10.0, 15.0, 20.0) glasses with various concentration of gadolinium (III) oxide using conventional melt-quenching technique. The prepared glasses were subjected to spectroscopic analysis for understanding their behaviour in optical and photoluminescence properties. The absorption bands of the prepared samples were investigated using absorption spectroscopy between 300 nm and 1700 nm. The stimulation from ground level ⁴I_15/2 caused significant (Er³⁺ ions) absorption peaks to develop. The branching ratio, fluorescence full width at half maximum of NIR emission, and lifetime, of I_13/2 level have all been assessed together with the Judd-Oflet parameters Ω_λ (λ = 2, 4, 6). The absorption and emission cross-sections were assessed using the Judd-Ofelt and McCumber hypothesis. The reported values are sufficiently consistent to be taken into consideration for prospective application in the optical communication windows in C and L bands.
Impact of samarium ion concentration on the physical, structural and optical properties of multi-component borate glasses
2022, Journal of Non-Crystalline Solids
The new glass system Borate-Sodium-Zirconium glasses activated with various concentration of samarium ion were successfully synthesized via melt quench method and their physical, structural and optical properties have been examined. The amorphous nature as well as various functional group that occur in the matrix are confirmed through XRD and FTIR measurements. All the physical parameters were calculated and contemplated to understand the impact of Sm₂O₃ concentration on host glass. The obtained optical bandgap from Tauc's plot has been utilized to calculate the refractive index and those were compared with standard formulae. Other optical parameters including numerical aperture, molar refractivity, electronic polarizability, oxide ion polarizability and optical basicity were determined. The metallization standard got less than one and the interaction parameter decreased with respect to increasing the Sm₂O₃ concentration. From the luminescence studies, 0.5 mol% of Sm³⁺ doped sample showed maximum intensity in the reddish-orange region. The colorimetric factors like orange/ red (O/R) intensity ratio, CIE coordinates and correlated color temperature (CCT) were also assessed. The results indicate that prepared BNSm glasses are suitable for visible lasers and orange-red luminescence devices.
Fluoroaluminate glasses with low phosphate content doped with Er3+/Yb3+ ions for up-conversion luminescence temperature sensors
2022, Materials Chemistry and Physics
Fluoroaluminate glasses with low phosphate content doped with Er³⁺-Yb³⁺ ions were synthesized and their upconversion luminescence was investigated as a function of temperature. The Judd-Ofelt theory was used to predict the transition probabilities, branching and to calculate fluorescence intensity ratio and thermal sensitivity of the glasses for the excited states of Er³⁺ions in the glasses. The effect of Er³⁺and Yb³⁺ ions concentrations and phosphate content on the upconversion luminescence was studied in the range 300–700 K. The fluorescence intensity ratio of the thermally coupled ²H_11/2 and ⁴S_3/2 levels of Er³⁺ions was studied to determine the thermal sensitivity of the glasses. It was found that the maximum absolute sensitivity S_max of the glasses under study varies in the range of 27–43 × 10⁻⁴ K⁻¹. The high values of S_max, high upconversion intensity and the ability of recording up-conversion spectra at low excitation powers make fluoroaluminate glasses with low phosphate content promising materials for optical temperature sensors.
Assessment of optical and fluorescence aspects of Er3+-doped multicomponent B<inf>2</inf>O<inf>3</inf>glasses as active media for 1.532 μm near-infrared optical amplifiers
2022, Journal of Materials Research and Technology
Current work principally provides an idea on controlling the Er³⁺: NIR (near-infrared) emission characteristics by changing a glass constituent and finding a suitable glass host favorable to design a novel C-optical band (1.53–1.565 μm) amplifier. By melting and rapid quench route, six transparent Er³⁺ (1 mol%)-doped B₂O₃-rich glasses having different single and mixed alkali ions were fabricated, and optical and fluorescence (visible and NIR) traits including Er³⁺ ion upper-levels ⁴S_3/2 and ⁴I_13/2 decay dynamics were inspected for such samples. At 1.4–1.65 μm wavelength range, an intense and wide NIR luminescence band centered at 1.532 μm (Er³⁺: ⁴I_13/2 → ⁴I_15/2 transition) has been obtained by a 980 nm laser diode pumping (⁴I_15/2 → ⁴I_11/2). NIR fluorescence Δλ_eff (effective bandwidth) varied depending on added single or mixed alkali ions, and a maximum Δλ_eff ∼74.66 nm was acquired for Er³⁺: Li ions constituting glass. For the ⁴I_13/2 → ⁴I_15/2 transition, σ_emi (stimulated emission cross-section) was evaluated using both Füchtbauer–Ladenburg and McCumber's theories. In all glasses, comparably, higher gain bandwidth (= 5.384 × 10⁻²⁶ cm³) and peak $σ_{e m i}^{M}$ (= 1.692 × 10⁻²⁰ cm²) values have been attained for ⁴I_13/2 → ⁴I_15/2 transition in Li ions containing sample, and also this glass possesses the largest σ_abs (absorption cross-section) (= 1.459 × 10⁻²⁰ cm²) for ⁴I_15/2 → ⁴I_13/2 transition. Further, at distinctive P (population inversion) values, gain spectra were computed, and all samples show C-optical band amplification beginning from P = 50%. All analyzed NIR fluorescence results indicate that Li ions having glass could be a potential gain medium for fiber amplifiers.
Investigation of spectroscopic and photoluminescence properties of Erbium doped phosphate (P<inf>2</inf>O<inf>5</inf>-K<inf>2</inf>O<inf>3</inf>-Al<inf>2</inf>O<inf>3</inf>) glasses
2022, Journal of Alloys and Compounds
Erbium (Er) doped P₂O₅-K₂O₃-Al₂O₃:Er₂O₃ glasses (KPEr) with different contents of Er³⁺ ions were fabricated by famous melt-quenching technique. The fabricated samples were characterized by using physical, X-ray photoelectron spectroscopy (XPS), photoluminescence, absorption, and J-O analysis techniques. The XRF analyses were performed in order to know the change in elemental composition of fabricated glasses, while using the various concentrations of Er³⁺ ions. Three emission peaks were observed, two peaks in visible regions of 526 nm (²H_11/2→⁴I_15/2) and 550 nm (⁴S_3/2→⁴I_15/2) and one peak in near infrared (NIR) region of 1545 nm (⁴I_13/2→⁴I_15/2). Nine peaks were observed in absorption spectra in the range of 390–1800 nm. The trend of JO parameters for the present KPEr6 glass sample is Ω₂> Ω₄> Ω₆. Higher values of stimulated emission cross-section σ_emi(λ), full wave half maxima FWHM and (FWHM x σ_emi (λ)), for KPEr6 indicate that the present glass has potential candidate to be used for broadband amplification in telecommunication. The McCumber theory is used to study absorption and emission cross-section for ⁴I_13/2→⁴I_15/2 transition. The luminescence colors of these samples were almost entirely fall in the yellow-green (Y-G) region (x = 0.33, y = 0.64) in the CIE 1931 diagram. The calculated CCT values for our prepared glasses were found to be 5554 K. The present study suggest that KPEr glass samples have potential candidate for broadband amplification in telecommunication, green LED and display devices.

View all citing articles on Scopus

View full text

Article preview

Journal of Non-Crystalline Solids

Abstract

Introduction

Section snippets

Experiment

Effect of glass composition on refractive index and effective linewidth

Effect of glass composition on refractive index and effective linewidth

Conclusions

Acknowledgements

References (25)

J. Non-Cryst. Solids

IEEE Photonics Tech. Lett.

J. Appl. Phys.

App. Phys. Lett.

SPIE

SPIE

SPIE

Electron. Lett.

IEEE Photonics Technol. Lett.

Jpn. J. Appl. Phys.

J. Opt. Soc. Am. B

Opt. Lett.

Cited by (262)

Insights on the structure and properties of sodium iron phosphate glasses from molecular dynamics simulations

Erbium doped gadolinium borate glasses for optical communication window applications

Impact of samarium ion concentration on the physical, structural and optical properties of multi-component borate glasses

Fluoroaluminate glasses with low phosphate content doped with Er<sup>3+</sup>/Yb<sup>3+</sup> ions for up-conversion luminescence temperature sensors

Assessment of optical and fluorescence aspects of Er<sup>3+</sup>-doped multicomponent B<inf>2</inf>O<inf>3</inf>glasses as active media for 1.532 μm near-infrared optical amplifiers

Investigation of spectroscopic and photoluminescence properties of Erbium doped phosphate (P<inf>2</inf>O<inf>5</inf>-K<inf>2</inf>O<inf>3</inf>-Al<inf>2</inf>O<inf>3</inf>) glasses