Fabrication and application of zirconia-erbium doped fibers

H. Ahmad; K. Thambiratnam; M. C. Paul; A. Z. Zulkifli; Z. A. Ghani; S. W. Harun

doi:10.1364/OME.2.001690

1. Introduction

The advent of the in-line optical amplifier in the later part of the 20th century acted as a catalyst for the exponential growth of optical communications around the world. In-line optical amplifiers or Fiber Optical Amplifiers (FOAs) were instrumental in overcoming the constraints inherent in electronic regenerators and allowed for the amplification of multiple signals simultaneously, thereby making possible the commercial communications networks that span the globe today [1–3]. Furthermore, recent technological advances have also opened up a variety of new prospects for FOAs, such as the generation of single and multi-wavelength fiber lasers [4,5], wavelength converters [6] and wide-band spectral sources [7], thus making the FOA a focal point of research and development.

The Erbium Doped Fiber Amplifier (EDFA) has long been the dominant technology for the development of FOAs due to its relatively low-cost per wavelength, low complexity and high stability [1,8]. However, the EDFA does have its limitations; most notably is that the concentration of erbium ions, the active medium of the FOA, cannot be increased significantly without encountering detrimental effects such as concentration quenching [9] and cluster formation [10]. In order to overcome this problem, and to address the rising need for compact and lower cost FOAs, research has now turned towards the exploration of new materials to act as hosts or co-dopants for the purpose of creating highly-doped EDFAs. In this regard, the element zirconium is a highly promising candidate towards achieving this goal. Zirconium ions co-doped in a silica host matrix demonstrate a high refractive index of over 1.45 in the visible and near infrared spectrum [11,12], thereby displaying wider emission and absorption bandwidths and allowing more channels to be amplified as compared to materials with a lower refractive index. This behavior is in accordance with the Fuchtbauer–Ladenberg relationship [13,14] and Judd–Ofelt theory [15,16]. Additionally, silica fibers co-doped with zirconium ions possess significant mechanical strength, are not hygroscopic and are able to resist to chemical corrosion. They also demonstrate excellent compatibility with conventional silica based optical fibers, thus making them useful for real-world applications.

Furthermore, zirconium co-doped fibers have demonstrated substantial non-linear characteristics. While detrimental towards high data-rate optical communications [17–19], non-linear phenomenon such as Four-Wave Mixing (FWM) and Self-Phase Modulation (SPM) have tremendous potential for the development of new, cost-effective applications such as multi-wavelength sources, wavelength converters and supercontinuum sources [20,21]. The FWM effect is of significant interest, due to its tremendous prospective in the development of stable and low cost multi-wavelength sources with channel spacings that are suitable for Dense Wavelength Division Multiplexing (DWDM) applications. However, generating the FWM effect is challenging due to the need to maintain phase matching between the propagating wavelengths, and the long lengths of fiber needed to generate the FWM effect make maintaining phase matching difficult. In this regard, the zirconium co-doped fiber is a promising candidate for generating the FWM effect, exhibiting non-linear behavior in only short fiber lengths [22] and therefore able to overcome the complexities of phase matching.

In this work, the fabrication and characterization of a Zirconium-Erbium co-Doped Fiber (Zr-EDF) is described, as well as its application as a non-linear gain medium and compact, linear gain medium for pulsed fiber lasers. The next section will examine the fabrication process, while the following section will detail the characterization of the physical and optical characteristics of the Zr-EDF. The successive sections will outline the application of the Zr-EDF, first as a non-linear gain medium for the generation of the FWM effect, and secondly as a short-length gain medium in a compact, passively Q-switched fiber laser using a graphene based Saturable Absorber (SA).

2. Fabrication

The fabrication of the Zr-EDF is a three-stage process. The process begins with the fabrication of a conventional silica preform using the Modified Chemical Vapor Deposition (MCVD) technique. Figure 1(a) shows the setup of the MCVD system, while Fig. 1(b) shows the actual system. The fiber preform is fabricated by passing SiCl₄ and POCl₃ vapors through a slowly rotating silica tube. An external flame source moves along the length of the tube as it rotates, heating the tube and its contents to a temperature of between 1350°C and 1400°C. This high temperature causes the chloride vapors to oxidize, and results in the deposition of a porous phospho-silica layer along the inner diameter of the silica tube.Once an even phospho-silica layer is obtained along the inner wall of the silica tube, the second stage of the fabrication process begins. In this stage, the silica tube with the porous phospho-silica layer on its inner wall undergoes a solution doping process where the glass modifiers ZrO₂, Y₂O₃, Al₂O₃ and Er₂O₃ are added. These modifiers are first mixed with an alcohol and water solution at a 1:5 ratio to form the complex ions ZrOCl₂.8H₂O, YCl₃.6H₂O, AlCl₃.6H₂O and ErCl₃.6H₂O that is then incorporated into the glass matrix of the silica tube by solution doping. At this stage also, small quantities of Y₂O₃ and P₂O₅ are added to the glass matrix to function as nucleating agents as well as to increase the phase separation of the Er₂O₃ doped micro-crystallites that form in the core matrix of the optical fiber preform. The concentration of the dopant constituents is optimized so as to give a fiber with a Numerical Aperture (NA) of 0.17 to 0.20. The addition of Y₂O₃ also serves a secondary purpose, which is to slow down or eliminate changes in the ZrO₂ crystal structure. This is because in a bulk glass matrix, pure zirconium can exist in three distinct crystalline phases, depending on the temperature range. At temperatures of above 2350°C, the ZrO₂ crystallites take on a cubic structure, while at lower temperatures of between 1170 and 2350°C they form a tetragonal structure instead and at temperatures of below 1170°C form a mono-clinic structure. The detrimental effect of these changes arises during the shift from the tetragonal to monoclinic phases, which is very fast and accompanied by an increase in volume of between 3 to 5%. This rapid increase causes significant cracking in the developed fiber during the cooling process (observed primarily in the core region, as this is where the concentration of ZrO₂ crystallites is the highest) and destroys the mechanical properties of the fiber. Adding a small amount of Y₂O₃, or oxides such as MgO, CaO can slow or stop down the changes in the crystalline structure, thereby preserving the mechanical strength and integrity of the fiber.

Fig. 1 (a) Setup of the MCVD system and (b) the formation of the silica preform.

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The final phase of the fabrication process involves the annealing of the fabricated preform after the solution deposition process. The preform is annealed at a temperature of 1100°C over a duration of 3 hours in a closed furnace, with a heating and cooling rate of 20°C/min so as to create Er₂O₃ and ZrO₂ rich micro-crystallites. Once the preform has been annealed, it is collapsed into a solid rod at a temperature of more than 2000°C and then drawn into a fiber strand with a 125.0 ± 0.5μm diameter through a conventional fiber-drawing tower. The temperature of 2000°C is below the melting temperature of the ZrO₂ crystallites but above the melting temperature of glass, thus allowing the ZrO₂ crystallites to retain their crystalline structure inside the silica glass matrix. Once the fiber has been drawn, the primary and secondary coatings, Desolite DP-1004 and Desolite DS-2015 is added to the fiber and the coating uniformity is assured by controlling the flow pressure of the inlet gases into the primary and secondary coating resin vessels during the drawing process, as well as the proper alignment of the primary and secondary coating cup units. The fiber diameter is also closely controlled during the drawing process to ensure that a high quality fiber is produced.

3. Optical characteristics of the Zr-EDF

Characterization of the Zr-EDF is carried out at both the preform stage and also using the completed fiber. Using selected preform samples, morphology of the core region was analyzed using a Field-Emission Gun Scanning Electron Microscopy (FEGSEM), while dopant concentration of each sample was determined using Electron Probe Microanalyses (EPMA). Two different preforms were prepared with different Er₂O₃ and ZrO₂ dopant levels by changing the composition of ErCl₃.6H₂O and ZrOCl₂.8H₂O during solution doping process, while the Al₂O₃ content is kept constant for both fiber samples. These preforms, and the resultant fibers drawn from them are designated as ZEr-A and ZEr-B. As the ZrO₂ crystallites are able to sustain their crystalline structures at high temperatures, above the temperature required to collapsed the silica rod and draw the fiber from the preform, therefore the existence of some ZrO₂ crystallites are expected within the host matrix of the preform. The microstructure of the doping region of ZEr-A and ZEr-B, which are developed without any thermal treatment or annealing, are given in Fig. 2 .

Fig. 2 The microstructure of the core region of the (a) ZEr-A preform and (b) the ZEr-B preform.

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The boundaries of the ZrO₂ crystallites in the glass matrix of the optical preform can be seen clearly in the figure, and it is observed that the boundaries of the ZrO₂ crystallites are larger and better defined in ZEr-B than similar crystallites in ZEr-A. This is attributed to the higher concentration of ZrO₂ used in the fabrication of ZrO₂. The results of the EPMA analysis of the dopant concentrations for the fabricated fibers are given in Table 1 , which shows the Al₂O₃, ZrO₂ and Er₂O₃ dopant concentrations in ZEr-A and ZEr-B. Both fiber preforms have approximately the same Al₂O₃ dopant levels of about 24 to 25 mol%. However, the ZEr-B fiber has a much higher ZrO₂ dopant concentration, almost quadruple that of ZEr-A, as well as close an Er₂O₃ dopant concentration almost twice as high as that of ZEr-A.The physical characteristics of ZEr-A and ZEr-B are given in Table 2 . Both fibers have almost similar characteristics, except for a slightly different NA and effective area (A_eff), with ZEr-A having an NA and A_eff of 0.17 μm and 87 μm² respectively while ZEr-B has values of 0.20 and 75 respectively. Both fibers are also observed to have significantly higher background losses than standard erbium doped fibers, with ZEr-A and ZEr-B having background losses of 145 dB/km and 175 dB/km respectively at 1300 nm. These losses are much higher than that of standard erbium doped fibers, which have typical values of around 10 to 15 dB/km, and arises due to scattering from the nano-crystalline phases in the fibers.

Table 1. Dopant Concentration within Preform Core Region (ZEr-A and ZEr-B)

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Table 2. Physical Characteristics of the Completed Fibers (ZEr-A and ZEr-B)^a

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In the characterization of the completed optical fibers, the absorption and fluorescence lifetimes of the fabricated fibers are analyzed. The peak absorption of the fibers at 978 nm are determined to be 14.5 and 18.3 dB/m respectively for ZEr-A and ZEr-B, translating to an of erbium ion concentration of 2800 and 3888 ppm/wt for the respective fibers. The fluorescence curves of both the ZEr-A and ZEr-B annealed preforms and drawn fibers are shown in Fig. 3(a) , while the fluorescence decay curves of both fibers are given in Fig. 3(b). The fluorescence curves are obtained by laterally pumping the fibers at a 980 nm pump power of 100 mW, and it can be seen that the both the ZEr-A and ZEr-B fibers have fluorescence peaks at 1530 nm, as is expected from as the active medium for both fibers is erbium. The ZEr-B has a slightly higher emission power density as compared to the ZEr-A, which is expected due to the higher Er₂O₃ dopant concentration of ZEr-B. It is also observed that the spectral broadening of the drawn fibers are larger than that of the preforms; this is attributed to the phase change of the Er₂O₃ from micro-crystallites in the annealed preform into nano-crystallites as the fiber is drawn. The decay curves of both fibers are approximately the same as expected due to the active medium of both fibers being the same. However, the decay curve of ZEr-B shows that it has a slight shorter fluorescence lifetime. Taking this fact into account, together with the higher doping levels of Er₂O₃ and ZrO₂ in ZEr-B, indicates that the concentration-quenching phenomenon that is typical of erbium ions is strongly reduced through an increase in the doping levels of ZrO₂.

Fig. 3 (a) Fluorescence curve of ZEr-A and ZEr-B annealed preforms and drawn fibers, and (b) decay curves of ZEr-A (above) and ZEr-B (below). (Figures used with permission (these figures are reproduced and modified with the permission of the publisher of [22].))

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Based on the characterization of the Zr-EDF, it can be seen that the addition of zirconium ions into the glass matrix of the Erbium Doped Fiber (EDF) allows for the fabrication of highly doped fibers, which have many potential applications in the development of compact devices. The following sections will examine the applications of the Zr-EDF, in particular its non-linear characteristics and also its usage as a compact medium for the generation of short pulses.

4. Four-wave-mixing in the Zr-EDF

In addition to providing high gain in a short fiber length, the Zr-EDF has also garnered increasing interest due to its significant non-linear characteristics that arise from the addition of zirconium ions into the glass matrix of the EDF [1]. The FWM effect is of particular interest when it comes to the non-linear effects of the Zr-EDF, as it has significant potential for new applications such as multi-wavelength generation and wavelength conversion. The FWM effect is an optical Kerr effect, and occurs when two or more wavelengths propagate simultaneously in non-linear medium. The interaction of these wavelengths results in the scattering of the incident photons, which in turn produces a fourth photon, known as an idler, at a wavelength that does not coincide with the incident wavelengths as given by Eq. (1) [22]:

λ_{n e w_s i g n a l} = 2 λ_{p u m p} - λ_{s i g n a l}, λ_{n e w_s i g n a l} = 2 λ_{p u m p} + λ_{s i g n a l}

where

λ_{p u m p}

and

λ_{s i g n a l}

are the pump and signal wavelengths respectively, while

λ_{n e w_s i g n a l}

is the wavelength of the signal generated by the FWM process. The power of the generated signal,

P_{F W M}

can be computed as:

P_{F W M} = η γ^{2} P_{p}^{2} P_{s} e^{- α L} L_{e f f}^{2}

where

P_{p}

is the input pump power and

P_{s}

is the input signal power.

L_{e f f}

is the effective length of the fiber and is given as

L_{e f f} = \frac{1 - e^{- α L}}{α}

, with

L

being the fiber length and _$α$ is the fiber attenuation coefficient. The normalized FWM efficiency

η

, is given as

η = \frac{α^{2}}{α^{2} + Δ β^{2}} [1 + \frac{2 e^{- α L} (1 - \cos (Δ β L)}{{(1 - e^{- α L})}^{2}}]

, where the phase mismatch,

Δ β = \frac{2 π λ^{2}}{c} D Δ f^{2}

. The dispersion parameter can be given as

D = \frac{- 2 π c}{λ^{2}} β^{2}

and

β^{2}

is the group velocity dispersion parameter. The

γ

parameter is determined by bi-directional measurements of the FWM power, while the chromatic dispersion is determined from the wavelength detuning of the FWM Power Conversion Efficiency (PCE). Figure 4 shows the experimental setup used in the generation and measurement of the FWM effect:In the setup, two Tunable Laser Sources (designated TLS1 and TLS2) are used as the pump and signal sources. Each TLS has a tuning range from 1460 nm to 1640 nm and linewidth of 0.015 nm. TLS1 is used to generate the pump beam,

P_{p}

, fixed at 1560 nm with an average output power of 12.8 dBm. The signal beam,

P_{s}

has an average power 10.8 dBm with wavelengths of between 1552 nm to 1557 nm, and is generated by TLS2.

P_{p}

and

P_{s}

are combined by a 3 dB coupler with Polarization Controllers (PCs) used to obtain the maximum FWM efficiency. Two Laser Diodes (LDs) pumps at 1460 nm and 1490 nm are used to pump the Zr-EDF through a Wavelength Division Multiplexer (WDM) in order to suppress the erbium ions and allow interaction between the propagating beams and the host medium which contain the zirconium ions. A 4 m long ZEr-B fiber, with the characteristics as described in Tables 1 and 2, is used as the non-linear medium. An Optical Spectrum Analyzer (OSA) with a 0.02 nm resolution bandwidth completes the optical circuit and is used to measure the generated FWM spectrum.

Fig. 4 Experimental setup for FWM generation and measurement in the Zr-EDF (a similar configuration as in [22]).

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Figure 5(a) shows both the theoretical as well as the actual value of $P_{F W M}$ for different $P_{p}$ wavelengths. It can be seen that the actual values of $P_{F W M}$ agree well with the theoretically predicted values of Eq. (2), with the highest $P_{F W M}$ value of about – 45 dBm obtained at a $P_{p}$ region of between 1558 nm to 1565 nm. Similarly, the wavelengths of the idlers generated auger well with their predicted values, as shown in Fig. 5(b). With the wavelength of $P_{p}$ fixed and the wavelength of $P_{s}$ varied by 1 nm, two sets of idler wavelengths are formed at $C$ and $S$ , with $C$ corresponding to $λ_{n e w_s i g n a l} = 2 λ_{p u m p} - λ_{s i g n a l}$ and $S$ corresponding to $λ_{n e w_s i g n a l} = 2 λ_{p u m p} + λ_{s i g n a l}$ .From the obtained values of $P_{F W M}$ , $C$ and $S$ , the non-linear coefficient as well as the chromatic and dispersion slopes can be determined. In the case of the ZEr-B fiber, the obtained non-linear coefficient, chromatic slope and dispersion slope is determined to be 14 W⁻¹km⁻¹, 28.45 ps/nm.km and 3.63 ps/nm².km respectively. Furthermore, the non-linear coefficient remains constant for all wavelengths propagating in the fiber, thus giving the ZEr-B fiber a very high potential for use in a multitude of applications such wavelength conversion and wavelength generation.

Fig. 5 (a) Theoretical and actual values of P_FWM against different P_p wavelengths, and (b) generation of idler wavelengths C and S at different P_s wavelengths. (These figures are reproduced with the permission of the publisher of [22].)

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5. Generation of short pulses using the Zr-EDF

In addition to its non-linear characteristics, the high concentration of erbium ions in a short length of fiber also provides the Zr-EDF with a significant advantage in the development of compact pulse fiber lasers. These lasers have recently garnered significant attention, and of particular interest are Q-switched fiber lasers, which provide high-energy pulses for applications such as in medicine, range-finding and sensing [23–27]. In this regard, a compact passively Q-switched pulse fiber laser can be realized by combining the Zr-EDF with an SA based on graphene, due to its relatively easy fabrication and low-cost [28–30].

Figure 6 shows the setup of the fiber laser, using a 3 m long ZEr-B fiber as the linear gain medium together with a graphene based SA as the Q-switching mechanism, as well as the setup used to create the graphene layer that will act as the SA for this work.

Fig. 6 (a) Setup of the passively Q-switched ZEr-B fiber ring laser using a graphene based SA, and (b) the setup for the deposition of the graphene layer onto the fiber ferrule.

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As shown in Fig. 6(a), the ZEr-B fiber is pumped by a 980 nm laser diode through a 980 / 1550 nm WDM. The ZEr-B fiber is also connected to an Optical Circulator (OC), which is in turn connected to a Fiber Bragg Grating (FBG) with a center wavelength of 1550 nm and a reflectivity of approximately 98.9% that acts to lock the wavelength propagating in the laser cavity. A 70:30 coupler is used to extract a portion of the signal for analysis, while the graphene based SA is placed within the cavity to generate the desired pulses. The extracted signal passes through a 3 dB coupler, with one half being directed to an OSA and the other half connected to a photodiode and oscilloscope. The graphene based SA is fabricated by depositing an emulsion containing graphene flakes suspended in a N-Methyl Pyrrolidone (NMP) onto the face of Fiber Ferrule 1 as illustrated in Fig. 6(b). A 1550 nm beam, at a high power of about 11 dBm then illuminates the fiber ferrule, causing some of the NMP solution to evaporate and leaving a thick layer of graphene. Fiber Ferrule 1 is then connected to Fiber Ferrule 2 so as to sandwich the graphene layer and the TLS turned on, while the output power is recorded by the Optical Power Meter (OPM). After some time, the TLS is shut off and Fiber Ferrule 2 removed. During this process, a portion of the graphene is transferred between the fiber ferrules, thus making the layer of graphene on Fiber Ferrule 1 thinner. Fiber Ferrule 2 is cleaned and the process repeated until the power of the OPM is 4.1% of the power of the input beam, with the reflection for a single layer of graphene contributing approximately 0.1% [31] and Fresnel reflection contributing the remaining 4.0%. Once this power is achieved, the assembly of Fiber Ferrules 1 and 2 now form the SA.

The compact ZEr-B based Q-switch laser performs adequately, generating pulses with a pulse width of 8.8 µs and repetition rate of 9.15 kHz at a pump power of 121.8 mW. The pulses generated are also stable over time and display minimal noise. Figure 7 provides a snapshot of an individual pulse generated as well as the pulse train obtained at a pump power of 121.8 mW.

Fig. 7 Q-switched pulse width (left) and pulse train (right) obtained at a pump power of 121.8 mW.

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Figures 8(a) and 8(b) show the pulse width and pulse repetition rate as a function of pump power as well as the average output power against pump power for the ZEr-B based Q-switched fiber laser. As can be seen in Fig. 8(a) the pulse width decreases while the repetition rate increases with as the pump power is raised. Although the availability of equipment limits the testing to a maximum pump power of 121.8 mW, the trends demonstrated by the fiber laser indicate that higher pump powers will undoubtedly results in smaller pulse widths and higher repetition rates. Furthermore, the average output power and pulse energy of the fiber laser also increases as the pump power is increased, as shown in Fig. 8(b). This increase is observed to be linear, with a slope value of about 0.45 µW/mW, and a maximum average output power of 161.35 µW (although it is expected that with a higher pump power and optimized cavity length, a higher average output power can be obtained). The pulse energy also increases linearly, with a slope of about 0.83 nJ/mW and a maximum pulse energy value of 17.64 nJ. These characteristics are typical of a highly doped erbium based fiber laser.It can be seen that the Zr-EDF, in particular the ZEr-B variant has a very high potential for a multitude of applications, from the development of multi-wavelength sources from its non-linear behavior to the fabrication of compact pulsed laser sources. The exploration into the capabilities of the Zr-EDF is only at its beginning; there is no doubt that additional research in the future will yield many more useful applications for this type of fiber.

Fig. 8 (a) Repetition rate and pulse width of the ZEr-B Q-switched fiber laser against different pump powers and (b) average output power and pulse energy of the ZEr-B Q-switched fiber laser against different pump powers.

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6. Conclusion

The fabrication and characterization of the Zr-EDF is described, as well as its uses in generating the FWM effect and also as a compact, passively Q-switched fiber laser. The Zr-EDF is made by first fabricating a conventional silica preform using the MCVD technique at between 1350°C and 1400°C, following which glass modifiers and nucleating agents such as ZrO₂, Y₂O₃, Al₂O₃, Er₂O₃ and P₂O₅ are added by solution doping. The resulting preform is then collapsed and annealed at a temperature of more than 2000°C to produce an optical fiber with a diameter of 125.0 ± 0.5 µm. Two Zr-EDFs are fabricated, designated ZEr-A and ZEr-B with erbium ion concentrations of 2800 and 3888 ppm/wt and absorption rates of 14.5 and 18.3 dB/m at 978 nm respectively. In the generation of the FWM effect, a 4 m long ZEr-B is used as the non-linear gain medium, and generates an FWM output with a power of - 45 dBm when pumped between 1558 nm to 1565 nm as predicted theoretically. The wavelengths of the generated sidebands also agree well with theoretical predictions, showing stability and potential applications as a multi-wavelength source. The ZEr-B is has a non-linear coefficient of 14 W⁻¹km⁻¹ and chromatic and slope dispersion values of 28.45 ps/nm.km and 3.63 ps/nm².km. The ZEr-B is also used to create a compact, passively Q-switched fiber laser together with a graphene based saturable absorber, and is capable of generating short pulses with a pulse width of 8.8 µs and repetition rate of 9.15 kHz at a pump power of 121.8 mW. The proposed fiber laser has a maximum average output power of 161.35 µW and maximum pulse energy value of 17.64 nJ, and has significant potential for further development as a compact, pulsed laser source.

Acknowledgments

The authors wish to express their gratitude to MOHE for their funding (UM.C/HIR/MOHE/SC/01) as well as to N. A. Awang of the Faculty of Science, Technology and Human Development, Universiti Tun Hussein Onn Malaysia, 86400 Batu Pahat, Johor Darul Takzim for her assistance and support in this work.

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Preform	Al₂O₃ (mol%)	ZrO₂ (mol%)	Er₂O₃ (mol%)
ZEr-A	0.25	0.65	0.155
ZEr-B	0.24	2.10	0.225

Preform	Core Composition	Core Diameter (μm)	Fiber Type	NA	A_eff (μm²)	Background Loss at 1300 nm (dB/km)
ZEr-A	SiO + Al₂O₃ + P₂O₅-ZrO₂-Y₂O₃ + Er₂O₃	10.5	Circular core with normal resin	0.17	87	145
ZEr-B	SiO + Al₂O₃ + P₂O₅-ZrO₂-Y₂O₃ + Er₂O₃	10.0	Circular core with normal resin	0.20	75	175

Preform	Al₂O₃ (mol%)	ZrO₂ (mol%)	Er₂O₃ (mol%)
ZEr-A	0.25	0.65	0.155
ZEr-B	0.24	2.10	0.225

Preform	Core Composition	Core Diameter (μm)	Fiber Type	NA	A_eff (μm²)	Background Loss at 1300 nm (dB/km)
ZEr-A	SiO + Al₂O₃ + P₂O₅-ZrO₂-Y₂O₃ + Er₂O₃	10.5	Circular core with normal resin	0.17	87	145
ZEr-B	SiO + Al₂O₃ + P₂O₅-ZrO₂-Y₂O₃ + Er₂O₃	10.0	Circular core with normal resin	0.20	75	175

Fabrication and application of zirconia-erbium doped fibers

Abstract

1. Introduction

2. Fabrication

3. Optical characteristics of the Zr-EDF

4. Four-wave-mixing in the Zr-EDF

5. Generation of short pulses using the Zr-EDF

6. Conclusion

Acknowledgments

References and links

Cited By

Figures (8)

Tables (2)

Equations (2)

Optical Materials Express