Al-codoped silica optical fiber based on atomic layer deposition method

Applied Surface Science 349 (2015) 287–291

Contents lists available at ScienceDirect

Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc

Photoluminescence properties of Bi/Al-codoped silica optical fiber based on atomic layer deposition method Jianxiang Wen a,∗ , Jie Wang a , Yanhua Dong a , Na Chen a , Yanhua Luo b , Gang-ding Peng b , Fufei Pang a , Zhenyi Chen a , Tingyun Wang a,∗∗ a

Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072, PR China Photonics & Optical Communications, School of Electrical Engineering & Telecommunications, University of New South Wales, Sydney 2052, NSW, Australia b

a r t i c l e

i n f o

Article history: Received 2 January 2015 Received in revised form 8 April 2015 Accepted 17 April 2015 Available online 27 April 2015 Keywords: Photoluminescence property Bi/Al-codoped silica materials Atomic layer deposition Silica optical fiber

a b s t r a c t The Bi/Al-codoped silica optical fibers are fabricated by atomic layer deposition (ALD) doping technique combing with conventional modified chemical vapor deposition (MCVD) process. Bi2 O3 and Al2 O3 are induced into silica optical fiber core layer by ALD technique, with Bis (2,2,6,6-tetra-methyl-3,5heptanedionato) Bismuth(III) (Bi(thd)3 ) and H2 O as Bi and O precursors, and with Al(CH3 )3 (TMA) as Al precursor, respectively. The structure features and optical properties of Bi/Al-codoped silica optical fibers are investigated. Bi2 O3 stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence state of Bi element is +3. Concentration distribution of Si, Ge and O elements is approximately 24–33, 9 and 66 mol%, respectively, in fiber preform core and cladding layer region. Bi and Al ions have been also slightly doped approximately 150–180 and 350–750 ppm in fiber preform core, respectively. Refractive index difference of the Bi/Al-codoped fiber is approximately 0.58% using optical fiber refractive index profiler analyzer. There are obvious Bi-type ions absorption peaks at 520, 700 and 800 nm. The fluorescence peaks are at 1130 and 1145 nm with 489 and 705 nm excitations, respectively. Their fluorescence lifetimes are 701 and 721 ␮s, respectively. And then there are obvious fluorescence bands in 600–850 and 900–1650 nm with 532 nm pump exciting. There is a maximum fluorescence intensity peak at 1120 nm, and its full wave at half maximum (FWHM) is approximately 180 nm. These may mainly result from the interaction between Bi and Al ions. The Bi/Al-codoped silica optical fibers would be used in high power or broadly tunable laser sources, and optical fiber amplifier in the optical communication fields. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Bismuth oxide is an interesting material with many promising applications. In 2001, Fujimoto etc. discovered a new infrared luminescence in bismuth-doped silica glass [1]. In recent years, the luminescent materials were demonstrated that they were a promising candidate for optical amplifier in the second telecommunication window [2,3]. Since then the bismuth-doped materials have been studied widely. The broadband luminescence of Bidoped glasses [4,5] and optical fibers [6,7] in the near-IR region covers from 1.1 ␮m to 1.8 ␮m, while these spectral region’s fiber

∗ Corresponding author. Tel.: +86 2156333172. ∗∗ Corresponding author. E-mail addresses: [email protected] (J. Wen), [email protected] (T. Wang). http://dx.doi.org/10.1016/j.apsusc.2015.04.138 0169-4332/© 2015 Elsevier B.V. All rights reserved.

lasers and broadband sources are very promising for a number of important applications. In 2005, the first bismuth-doped fiber was fabricated by the modified chemical vapor deposition (MCVD) method [8]. In the following years, some bismuth-doped fiber lasers and amplifiers in the wavelength 1100–1550 nm were also reported [9–12]. Now, the fabrication technologies of Bi-doped fibers like rareearth doped fibers, are mainly using MCVD, and combining with solution doping technique [13,14]. However, the combining technology lacks of uniformity, and doping materials are easily volatilize in high temperature, which have limited the excellent performance for the doped fibers’ fabrication. Atomic layer deposition (ALD) is a chemical vapor deposition technique based on the sequential use of self-terminating gas–solid reactions, and that is a self-limiting surface reaction [15], whose advantages [16] include good uniformity, favorable dispersibility, and high doping concentration as a novel method. At present, there are only few reports

288

J. Wen et al. / Applied Surface Science 349 (2015) 287–291

Fig. 1. XPS spectrum of the Bi/Al-codoped silica optical fiber material, (inset) atomic ratio of Bi, Si and O elements.

about the preparation of rare earth optical fiber by ALD [17–19]. However, the Bismuth oxide induced into silica optical fiber core by ALD technique and its optical properties was seldom reported. In this paper, we present a new doping method for Bi/Alcodoped silica optical fibers combining ALD with MCVD technique, investigate their structure features and optical properties, and confirm its stoichiometry using XPS. For the Bi/Al-codoped silica optical fibers, there are typical absorption peaks at 520, 700 and 800 nm. Their fluorescence peaks are near 1130 and 1145 nm with 489 and 705 nm excitation, respectively. Fluorescence lifetimes are also 701 and 721 ␮s, respectively. These are good optical properties for its potential applications in the specialty optical fiber lasers and the growing demands of both existing and forthcoming optical communication systems. 2. Experiments 2.1. Formation process of Bi2 O3 During the deposition process of Bi2 O3 using ALD, a silica plate is placed in the silica substrate tube, which is used for XPS analysis with a monochromatic Al K␣ (1486.6 eV) as X-ray source (Kratos AXIS Ultra DLD, England). It can confirm the stoichiometry of the bismuth oxide as shown in Fig. 1. The figure shows the presence elements including Bi, O and Si elements. The center of binding energy of Bi 4f7/2 is about 158.0 eV, The main peaks of Bi(4f) emission at 156.5 and 160.8 eV can be assigned to Bi 4f7/2 and Bi 4f5/2 , these values correspond to Bi3+ , which is basically agreement with the bind energy of Bi2 O3 (158.8 eV). These indicate that the valence state of Bi ion is +3. Therefore, there is main Bi2 O3 existing on silica substrate using ALD doping technique. And then the doping concentrations of ions are [Bi] = 21.19 mol %, [Si] = 11.99 mol %, and [O] = 66.82 mol%, respectively, as shown in the down right corner of Fig. 1. 2.2. Fabrication of Bi/Al-codoped optical fiber Bi/Al-codoped silica optical fiber is fabricated by ALD technique combining with MCVD technology [20]. The fabrication process can be divided into four steps: Firstly, a porous soot layer is deposited inside silica substrate tube using MCVD process; During the process, chemical reactions in the gas form a fine soot of silica, which coats the inner surface of the substrate tube and is sintered into a semi-clear soot layer; Secondly, Bi and Al ions are induced on the surface of the porous soot layer using ALD technique (TFS-200, Beneq, Finland), which is a self-limited chemical vapor deposition,

and here is applied in the doping materials deposition for optical fiber; Thirdly, germanium ion is doped by MCVD, as optical fiber core layers, and then a Bi/Al-codoped optical fiber preform with a Ge-doped higher index core is formed by MCVD collapsing process; At last, The preform is finally drawn into fibers with typical dimensions of single mode fiber. Its diameters of cladding and core layers are about 124.0 and 9.0 ␮m, respectively. For Bi2 O3 , the precursor is Bis(2,2,6,6-tetra-methyl-3,5heptanedionato) Bismuth(III) (Bi(thd)3 ) (supplied by Shanghai J&K Scientific Ltd.), and then participates in chemistry reaction with H2 O. Al(CH3 )3 (TMA) is used as the precursor of Al2 O3 . It is noticed that O3 originated from O2 . The temperature of Bi(thd)3 precursor is controlled about 100–250 ◦ C. In the deposition process, the substrate temperature is around 150–350 ◦ C. And the high pure nitrogen is used as a carrier gas with a flow rate of 100 sccm (standard-state cubic centimeter per minute). Al2 O3 is deposited ˚ with deposition rate approximating 0.94 A/cycle [21]. The reaction mechanism [22] of Bi(thd)3 and H2 O can be described with Eqs. (1)–(3): the whole reaction can be described in Eq. (1) 2Bi(thd)3 + 3H2 O → Bi2 O3 + 6H-thd

(1)

A process is that hydroxyl on silicon reacts with Bi source to obtain Si O Bi(thd)2 , as shown in Eq. (2). B process is that Si O Bi(OH)2 is obtained by the reaction with H2 O, and Si O Bi(thd)2 terminated by hydryl groups, as described in Eq. (3). Repeat ABAB operations, the desired Bi-doped thickness is obtained. And Al2 O3 formation mechanism is analogous to these. A : Si OH + Bi(thd)3 → Si O Bi(thd)2 + H-thd

(2)

B : Si O Bi(thd)2 + 2H2 O → Si O Bi(OH)2 + 2H-thd

(3)

2.3. Measurements section The emission spectra, excitation spectra and fluorescence decay curves are measured with a high resolution spectrofluorometer (FLSP 920, Edinburgh Instruments Inc., English) equipped with a red sensitive single photon counting photomultiplier (Hamamatsu R928P) in Peltier air-cooled housing. A microsecond pulsed Xenon flash lamp ␮F900H with an average power of 60 W, which can measure decays from 1 ␮s to 10 s, is used to measure decay curves of Bi/Al-codoped fiber preform. The measurement is performed at room temperature. Absorption spectra are measured by cut-back technique using a broadband optical spectrum analyzer (OSA, Yokogawa AQ-6315A) in the 400–1700 nm wavelength region, and resolution is 10 nm. Fluorescence spectra are measured by 532 nm backward pumping at room temperature. The optical fiber length of measuring absorption spectra is 20 cm, and that of testing luminescence spectra is 3.2 m with 532 nm pump. 3. Experimental results and discussion The refractive index difference is measured by optical fiber analyzer (S14, Photon Kinetics Inc., USA), as shown in Fig. 2. The index difference between the core and the cladding is n = 0.58%. The core and cladding diameter of fiber is approximately 9.09 and 123.67 ␮m, respectively. In addition, number aperture NA = 0.132. The cross-section of the optical fiber is also shown in Fig. 2. The absorption spectrum of the Bi/Al-codoped optical fiber using cut-back technique is shown in Fig. 3. We can see that the fiber exhibits several absorption bands at 450, 520, 700, 800 and 1000 nm. These are the type-absorption peaks of Bi ions [1]. And the intensity of the absorption peaks at 520 and 700 nm are relatively stronger. The background attenuation at 1500 nm is approximately

J. Wen et al. / Applied Surface Science 349 (2015) 287–291

289

Fig. 2. Refraction index difference and cross-section of Bi/Al-codoped silica optical fiber.

1.7 dB/m and hydroxyl (OH ) absorption is about 4.1 dB/m. However the absorption coefficients at 520 and 700 nm bands are 115 and 90 dB/m, respectively, which is a little high due to the higher doping concentration of Bi/Al materials. Furthermore, the contents of the optical fiber perform materials are analyzed. The test samples are prepared by cutting into slices from the same optical fiber preform, with about 1 mm thickness. And then composition of the fiber preform material is tested by Electron Probe Micro-Analyser (EPMA, JEOL JXA-8100, University of Lille 1, France), as shown in Fig. 4. It can be seen that concentration of Si in core and cladding layer region is approximately 24–33 mol%. Ge-doping is to increase refractive-index of the fiber core, whose concentration is approximately 4–9 mol% in core layer region. And concentration of O in fiber core and inner cladding region, distributed uniformly, is approximately 66 mol%. In Fig. 4(b), we could see that the Bi ion has been slightly doped successfully into the fiber core region approximately 150–180 ppm and Al ion has been doped with 350–750 ppm in fiber core and inner cladding region. We also carried out emission spectra and fluorescence decay measurements for Bi/Al-codoped fiber preform samples, and the results are shown in Figs. 5 and 6. Excitations into 489 and 705 nm the emissions spectra are observed, and the emission peaks are at 1145 and 1131 nm, respectively. The FWHMs are about 170 and 145 nm, respectively, as shown in Fig. 5. When the fiber preform sample is excited with 705 nm, the fluorescence lifetime of emission peak at 1131 nm is about 701 ␮s. Then the sample is excited with 489 nm, the fluorescence lifetime of emission peak at 1145 nm is 721 ␮s, as shown in Fig. 6. The

150

fluorescence properties are further analyzed. The emission crosssections  em can be estimated from the Füchtbauer–Ladenburg by assuming a Gaussian-shaped emission band [13,23,24], as shown in Eq. (4).

em (0 ) =

20 4n2 

 ln 2 1/2 1 

v

6.0 Bi ions absorption 5.4 Absorption (dB/m)

120

Absorption (dB/m)

Fig. 4. Concentration distribution of the doping material (various elements) in the Bi/Al-codoped fiber preform.

90

60

4.8 _

OH absorption

4.2 3.6 3.0 2.4 1.8 1200

1280

30

1360 1440 1520 Wavelength (nm)

1600

_

OH absorption

0 400

600

800

1000

1200

1400

1600

Wavelength (nm) Fig. 3. Optical absorption spectrum of the Bi/Al-codoped silica optical fiber.

Fig. 5. Emission spectra of Bi/Al-codoped fiber preform samples.

(4)

290

J. Wen et al. / Applied Surface Science 349 (2015) 287–291

Table 1 Fluorescence properties of literatures’ and experiments’ samples.  em × FWHM (×10−20 cm2 nm)

 em ×  (×10−21 cm2 ms)

Refs. or Expts.

8.0 9.6

136 139

5.6 6.9

Expts Expts

750 1 000

6.0 6.0

86 90

4.5 6.0

[13] [14]

510 500 456 273 222

11.3 10.0 9.6 15.5 15.9

210 304 305 499 639

4.43 5.0 4.4 4.2 3.5

[24] [25] [26] [27] [28]

Preparation technique

Fluorescence peak (nm)

FWHM (nm)

Fluorescence lifetime (␮s)

ALD& MCVD (Silica)

1131 1145

170 145

701 721

MCVD& Solution method (Silica)

1140 1150

143 150

Melting method (Glass samples)

1185 1300 1265 1280 1310

186 304 318 322 401

 em (×10−21 cm2 )

where 0 is the peak wavelength, n is the refractive index of the fiber core layer,  is the fluorescence lifetime, and v is the linewidth of peak wavelength, which is shown in Eq. (5). v =

c 0

2



(5)

where, c is the velocity of light,  is the FWHM of the emission spectrum. We can obtain  em = 8.0 × 10−21 cm2 , with 0 = 1131 nm, n = 1.4618,  = 701 ␮s, and  = 170 nm with 705 nm excitation, and  em = 9.6 × 10−21 cm2 , with 0 = 1145 nm, n = 1.4618,  = 721 ␮s, and  = 145 nm for it with 489 nm excitation. The product of the emission cross-section ( em ) and the fluorescence lifetime () is an important parameter to characterize laser materials, because the laser threshold is proportional to ( em × )−1 , that is, for different excitation wavelengths,  em ×  are 5.6 × 10−21 and 6.9 × 10−21 cm2 ms, respectively, and it is the same to  em × FWHM, as listed in Table 1. At the same time, we make a comparison of our experiments’ and literatures’ values, as shown in Table 1. According to Table 1, it is clear to see that the FWHM of Bi/Alcodoped fiber became a little wider than that of literatures reported (the Bi-doped silica optical fiber samples are fabricated using MCVD combining with solution method) or almost the same value, by combining with both fluorescence characteristics. The emission cross section  em of Bi-doped optical fiber, prepared with ALD and MCVD techniques, shows more 1.6 times than that of the Bi-doped fiber fabricated by solution method and MCVD technique. On the other hand, the  em × FWHM values of our experiments are about 1.5–1.85 times larger than that of the Bi-doped fiber fabricated with solution method, and  em ×  value is almost the same, which was also reported in [13,25]. However, for the Bi-doped glass samples, that is a matrix of the host glass, the fluorescence lifetimes are all shorter, and then the  em ×  value of the Bi-doped glass samples is smaller than that of the Bi-doped silica optical fibers, as listed in Table 1. Thus, it is considered that Bi-doped silica optical

Fig. 6. Fluorescence decay curves of Bi/Al-codoped fiber preform samples.

Fig. 7. The excitation spectrum of Bi/Al-codoped silica optical fiber preform.

fiber prepared with ALD and MCVD techniques may be better than that of solution method and MCVD technique. It indicates that the ALD combing with MCVD is a promising fabrication technique for Bi-doped silica optical fibers. To further investigate the optical spectrum characteristics of Bi/Al-codoped fiber preform, we measured its excitation spectrum at emission peak 1131 nm, as shown in Fig. 7. We can see that there are three excitation bands, 300, 500 and 700 nm, and the 500 nm is main excitation band. According to the excitation spectrum in Fig. 7 and absorption spectrum in Fig. 3, we choose 532 nm band as pump source. The fluorescence spectrum of the optical fiber is measured with backward pump method, as shown in Fig. 8. Fiber length is 3 m. Pump power launched into the Bi/Al-codoped silica optical fiber is 200 mW. There are obvious fluorescence bands in 600–850 and 900–1650 nm region. Then there are some saw-tooth

Fig. 8. Fluorescence spectrum of Bi/Al-codoped silica optical fiber with 532 nm laser pump.

J. Wen et al. / Applied Surface Science 349 (2015) 287–291

shape peaks at 600–850 nm bands, which are mainly due to coupler effect. There is a maximum fluorescence intensity peak at 1120 nm, and its FWHM is about 180 nm. These may mainly result from the interaction between Bi and Al ions. In the fluorescence band region, efficient visible lasers may be generated, in particular yellow-light sources, by frequency doubling. It is known that the 570–580 nm bands are very promising for ophthalmology and dermatology applications [29]. Besides, there is a high brightness 589 nm source for laser guide stars [30]. 4. Conclusions In this work, we report a new method of fabricating Bi/Alcodoped silica optical fiber. We combine ALD and MCVD technology to obtain Bi-doped fibers and induced Bi and Al ions into optical fiber core layer by ALD technique with Bi(thd)3 and H2 O as Bi and O precursors, and with TMA as Al precursor, respectively. During the preparation process, we investigated its structure features and Photoluminescence properties. The valence state of Bi ion is +3. Concentration distribution of Si, Ge and O elements is about 24–33, 4–9 and 66 mol%, respectively, in fiber preform core and cladding region. And the Bi and Al ions have been also doped about 150–180 and 350–750 ppm in fiber preform core, respectively. Refractive index difference of the Bi/Al-codoped fiber is approximately 0.58%. There are obvious Bi-type ions absorption peaks at 520, 700 and 800 nm bands. The fluorescence peaks are 1130 and 1145 nm with 489 and 705 nm exciting, respectively. And its fluorescence lifetimes are 701 and 721 ␮s, respectively. With 532 nm pump exciting, there are obvious fluorescence bands at 600–850 and 900–1650 nm bands. There is a maximum fluorescence intensity peak at 1120 nm, and its FWHM is about 180 nm. These may mainly result from the interaction between Bi and Al ions. We believe that this work can provide a new route and guidance to fabricate Bi/Al-codoped optical fibers with better optical properties. Next step we would fabricate the interesting silica optical fibers with high gain and ultra-broadband, and expect to the potential applications in broadly tunable laser sources and ultra-broadband optical fiber amplifiers in optical communication fields. Acknowledgments This work is supported by National Program on Key Basic Research Project (973 Program, Grant No: 2012CB723405); Natural Science Foundation of China (Grant Nos: 60937003, 61177088, 61275051, 61275090, 61227012, 61475096); Shanghai Natural Science Foundation (12ZR1411200); The authors are also thankful for the support through the International Science Linkages project (CG130013) by the Department of Industry, Innovation, Science and Research, Australia, and for two LIEF grants (LE0883038 and LE100100098) from the Australian Research Council to fund the national fiber facility at the University of New South Wales. References [1] Y. Fujimoto, M. Nakatsuka, Infrared luminescence from bismuth-doped silica glass, Jpn. J. Appl. Phys. 40 (2001) L279–L281. [2] Y. Fujimoto, M. Nakatsuka, Optical amplification in bismuth-doped silica glass, Appl. Phys. Lett. 82 (2003) 3325–3326. [3] T.Y. Wang, X.L. Zeng, J.X. Wen, F.F. Pang, Z.Y. Chen, Characteristics of photoluminescence and Raman spectra of InP doped silica fiber, Appl. Surf. Sci. 255 (2009) 7791–7793.

291

[4] M.Y. Peng, J.R. Qiu, D.P. Chen, X.G. Meng, I. Yang, X.W. Jiang, C.S. Zhu, Bismuthand aluminum-codoped germanium oxide glasses for super-broadband optical amplification, Opt. Lett. 29 (2004) 1998–2000. [5] E.M. Dianov, Amplification in extended transmission bands using bismuthdoped optical fibers, J. Lightwave Technol. 31 (2013) 681–688. [6] V.V. Dvoyrin, V.M. Mashinsky, L.I. Bulatov, I.A. Bufetov, A.V. Shubin, M.A. Melkumov, E.F. Kustov, E.M. Dianov, Bismuth-doped-glass optical fibers-a new active medium for lasers and amplifiers, Opt. Lett. 31 (2006) 2966–2968. [7] J.Z. Zhang, Z.M. Sathi, Y.H. Luo, J. Canning, G.D. Peng, Toward an ultra-broadband emission source based on the bismuth and erbium co-doped optical fiber and a single 830 nm laser diode pump, Opt. Express 21 (2013) 7786–7792. [8] V.V. Dvoyrin, V.M. Mashinsky, E.M. Dianov, A.A. Umnikov, M.V. Yashkov, A.N. Guryanov, Absorption, fluorescence and optical amplification in MCVD bismuth-doped silica glass optical fibres, in: ECOC 2005, 31st European Conference on IET, Opt. Commun. 4 (2005) 949–950. [9] S. Firstov, S. Alyshev, M. Melkumov, K. Riumkin, A. Shubin, E. Dianov, Bismuthdoped optical fibers and fiber lasers for a spectral region of 1600–1800 nm, Opt. Lett. 39 (2014) 692–69309. [10] E.M. Dianov, A.V. Shubin, M.A. Melkumov, O.I. Medvedkov, I.A. Bufetov, Highpower cw bismuth-fiber lasers, J. Opt. Soc. Am. B 24 (2007) 1749–1755. [11] E.M. Dianov, M.A. Melkumov, A.V. Shubin, S.V. Firstov, V.F. Khopin, A.N. Gur’yanov, I.A. Bufetov, Bismuth-doped fibre amplifier for the range 1300–1340 nm, Quantum Electron. 39 (2009) 1099–1101. [12] M.A. Melkumov, I.A. Bufetov, A.V. Shubin, S.V. Firstov, V.F. Khopin, A.N. Guryanov, E.M. Dianov, Laser diode pumped bismuth-doped optical amplifier for 1430 nm band fiber, Opt. Lett. 36 (2011) 2408–2410. [13] I. Razdobreev, L. Bigot, V. Pureur, A. Favre, G. Bouwmans, M. Douay, Efficient all-fiber bismuth-doped laser, Appl. Phys. Lett. 90 (2007), 031103-1-3. [14] E.M. Dianov, V.V. Dvoyrin, V.M. Mashinsky, A.A. Umnikov, M.V. Yashkov, A.N. Gur’yanov, CW bismuth fibre laser, Quantum Electron. 35 (2005) 1083–1084. [15] R.L. Puurunen, Surface chemistry of atomic layer deposition: a case study for the trimethylaluminum/water process, Appl. Phys. Rev. 97 (2005), 121301-1-52. [16] S.M. George, Atomic layer deposition: an overview, Chem. Rev. 110 (2010) 111–131. [17] S. Sneck, P. Soininen, M. Putkonen, L. Norin, A new way to utilize atomic layer deposition-case study: optical fiber manufacturing, in: Proc. AVS 6th International Conference on Atomic Layer Deposition, 2006. [18] J.J. Montiel i Ponsoda, L. Norin, C. Ye, M. Bosund, M.J. Söderlund, A. Tervonen, S. Honkanen, Ytterbium-doped fibers fabricated with atomic layer deposition method, Opt. Express 20 (2012) 25085–25095. [19] Y.H. Dong, J.X. Wen, F.F. Pang, Z.Y. Chen, J. Wang, Y.H. Luo, G.D. Peng, T.Y. Wang, Optical properties of PbS-doped silica optical fiber materials based on atomic layer deposition, Appl. Surf. Sci. 320 (2014) 372–378. [20] P.P. Wang, J.X. Wen, Y.H. Dong, F.F. Pang, T.Y. Wang, Z.Y. Chen, Bismuth-doped silica fiber fabricated by atomic layer deposition doping technique, in: Asia Communications and Photonics Conference, AW4C, vol. 5, Optical Society of America, Beijing, 2013, pp. 1–3. [21] Y. Zhao, F.F. Pang, Y.H. Dong, J.X. Wen, Z.Y. Chen, T.Y. Wang, Refractive index sensitivity enhancement of optical fiber cladding mode by depositing nanofilm via ALD technology, Opt. Express 21 (2013) 26136–26143. [22] Y.D. Shen, Y.W. Li, W.M. Li, J.Z. Zhang, Z.G. Hu, J.H. Chu, Growth of Bi2 O3 ultrathin films by atomic layer deposition, J. Phys. Chem. C 116 (2012) 3449–3456. [23] W.L. Barnes, R.I. Laming, E.J. Tarbox, P.R. Morkel, Absorption and emission cross section of Er3+ doped silica fibers, IEEE J. Quantum Electron. 27 (1991) 1004–1010. [24] J. Ruan, Y.Z. Chi, X.F. Liu, G.P. Dong, G. Lin, D.P. Chen, E. Wu, J.R. Qiu, Enhanced near-infrared emission and broadband optical amplification in Yb–Bi co-doped germanosilicate glasses, J. Phys. D: Appl. Phys. 42 (2009), 155102(1-6). [25] X.G. Meng, J.R. Qiu, M.Y. Peng, D.P. Chen, Q.Z. Zhao, X.W. Jiang, C.S. Zhu, Near infrared broadband emission of bismuth-doped aluminophosphate glass, Opt. Express 13 (2005) 1628–1634. [26] M.Y. Peng, B.T. Wu, N. Da, C. Wang, D.P. Chen, C.S. Zhua, J.R. Qiu, Bismuthactivated luminescent materials for broadband optical amplifier in WDM system, J. Non-Cryst. Solids 354 (2008) 1221–1225. [27] M.Y. Peng, C. Wang, D.P. Chen, J.R. Qiu, X.W. Jiang, C.S. Zhu, Investigations on bismuth and aluminum co-doped germanium oxide glasses for ultra-broadband optical amplification, J. Non-Cryst. Solids 351 (2005) 2388–2393. [28] M.Y. Peng, J.R. Qiu, D.P. Chen, X.G. Meng, C.S. Zhu, Superbroadband 1310 nm emission from bismuth and tantalum codoped germanium oxide Glasses, Opt. Lett. 30 (2005) 2433–2435. [29] N.S. Sadick, R. Weiss, The utilization of a new yellow light laser (578 nm) for the treatment of class I red telangiectasia of the lower extremities, J. Dermatol. Surg. 28 (2002) 21–23. [30] C.E. Max, S.S. Olivier, H.W. Friedman, J. An, K. Avicola, B.V. Beeman, H.D. Bissinger, J.M. Brase, G.V. Erbert, D.T. Gavel, K. Kanz, M.C. Liu, B. Macintosh, K.P. Neeb, J. Patience, K.E. Waltjen, Image improvement from a sodium-layer laser guide star adaptive optics system, Science 277 (1977) 1649–1651.