effect of fluorine ions on 2.7 μm emission in er 3+ /nd ...

Effect of Fluorine Ions on 2.7 μm Emission in Er3+/Nd3+-CodopedFluorotellurite GlassYanyan Guo,†,‡ Ming Li,†,‡ Lili Hu,† and Junjie Zhang†,*†Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences,Shanghai 201800, PR China‡Graduate School of Chinese Academy of Science, Beijing 100039, PR China

ABSTRACT: The 2.7 μm emission properties of Er3+/Nd3+-codopedfluorotellurite glasses were investigated in the present work. The thermalstability, refractive index, absorption and transmission spectra, and emissionspectra were measured and investigated. The 2.7 μm emission in Er3+/Nd3+-codoped fluorotellurite glasses was enhanced with the increase of fluorineions. The Judd−Ofelt analysis based on absorption spectra was performed inorder to determine the Judd−Ofelt intensity parameters Ωt (t = 2, 4, 6),spontaneous emission probability, radiative lifetime and branching ratios ofEr3+:4I11/2 → 4I13/2 transition. It is found that the Er3+/Nd3+-codopedfluorotellurite glass possesses a lower spontaneous transition probability A(58.95 s−1) but a higher branching ratio β (15.72%) corresponding to thestimulated emission of Er3+:4I11/2 → 4I13/2 transition. Additionally, thetransmittance was also tested and reached a maximum when the molarconcentration of ZnF2 is 15%. The presence of fluorine ions greatlydecreases the population of OH groups, which affects the 2.7 μm emission effectively by means of decreasing the rate of energytransfer to impurities (e.g., OH groups).

I. INTRODUCTIONThe investigation of solid state lasers operating in the mid-infrared wavelength region (2−5 μm) has been taken widely inthe past few years. Many potential applications, such as medicallasers, sensing, military counter-measures as well as lightdetection and ranging (LIDAR) were offered by the devicesoperating in the mid-infrared wavelength region.1−3 Lightsources in the 2.7 μm region are of great interest owing to thestrong absorption by water in this spectral region. Despite thelaser characteristics of the 2.7 μm (Er3+: 4I11/2→

4I13/2 self-terminating transition) are not satisfactory, Er3+ is an importantcandidate to provide 2.7 μm emission. Fortunately, codoping ofNd3+ has been demonstrated to enhance the 2.7 μmemission.4,5

In order to achieve strong emission at the 2.7 μm region, themain effort so far has been concentrated on the Er3+-dopedfluoride and chalcogenide glasses because of their low phononenergy which decreases the rate of nonradiative transitions.6,7

However, the applications of fluoride and chalcogenide glassesare limited due to their poor chemical durability and thermalstability. The oxide and oxyfluoride glasses possess bettercharacteristics in mechanical strength, thermal stability, andchemical durability than fluoride and chalcogenide glasses andthe successful observation of 2.7 μm emission from oxide andoxyfluoride glasses host stand only in a few glass systems up tonow.4,8−10 Because of the low phonon energy and goodphysicochemical properties of tellurite glasses, it is consideredto be a new candidate material for 2.7 μm emission. While, the

absorption around 3 μm ascribing to stretching vibration of freeOH groups and stronger hydrogen bond −O−H···O− arestrong in tellurite glasses which is one of the main impactfactors of 2.7 μm emission.11 The OH concentration could bedecreased in tellurite glass by introducing properly F ionsand then the quenching effect on 2.7 μm emission induced byOH groups may be depressed. Moreover, the fluorine ionsintroduced into the tellurite glass could modify thespectroscopic properties due to the formation of a localbonding environment of oxygen and fluorine with thecations.11,12

In present study, F ions were introduced into Nd3+/Er3+-codoped tellurite glass. The thermal stability, refractive index,absorption, mid-infrared transmittance and emission spectrawere investigated. Considering the presence of F ions, thestructure features from the Raman spectra were investigated tointerpret the physical and optical properties of the glasses.

II. EXPERIMENTSA. Preparation of Glass. The glass samples with molar

compositions of 60TeO2−15GeO2−20ZnO−5K2O−1Er2O3

(TE) and 60TeO2−15GeO2−(20−x)ZnO−(5−y)K2O−xZnF2−yKF−1Er2O3−0.5Nd2O3 (TF, x = 0, 5, 10, 15, 20; y= 0, 5) were prepared by conventional melting and quenching

Received: February 17, 2012Revised: May 16, 2012Published: May 23, 2012

Article

pubs.acs.org/JPCA

© 2012 American Chemical Society 5571 dx.doi.org/10.1021/jp301582b | J. Phys. Chem. A 2012, 116, 5571−5576

pubs.acs.org/JPCA

method. Mixed batches of ∼30 g were melted in a aluminacrucible at 1150 °C for about 30 min. Then the melts werepoured into stainless-steel molds and annealed for 10 h nearglass transition temperature. Samples were cut into arectangular (20 × 20 × 2 mm3) shape and optically polished.B. Measurements. Glass density (ρ) was measured by the

Archimede’s method using distilled water as immersion liquidwith maximum error of ±2%. Refractive indices of 633 and1064 nm were measured by a Spectro-Ellipsometer (WoollamW-VASE, error limit ±0.05%). The glass transition temperature(Tg) and crystallization beginning temperature (Tx) were testedby differential scanning calorimetry (DSC) measurement.Raman spectra in the range of 100−1000 cm−1 and 1000−2000 cm−1 were measured with a FT Raman spectropho-tometer (Nicolet MODULE) using the 788 nm excitation linefrom a spectra physics laser. Midinfrared transmittance spectrawere measured with a Perkin-Elmer 1600 series Fouriertransform infrared (FTIR) spectrometer in a wavenumberregion between 4000 and 2500 cm−1. Absorption spectra weretested in the range of 300−1600 nm with a Perkin-ElmerLambda 900UV/VIS/NIR spectrophotometer with 1 nm steps.The lifetime of Er: 4I13/2 level was measured by the FLSP920fluorescence spectrophotometer (Edinburgh Analytical Instru-ments Ltd.) pumped by 808 nm LD. Emission spectra in therange of 1400−1700 nm and 2550−2820 nm were obtained bya computer-controlled TRIAX 320 type spectrometer pumpedby 808 nm laser diode (LD). In order to accurately comparethe intensity of 2.7 μm emission, the position and power of 808nm LD and the width of the slit to collect signal were fixed tothe same condition and the samples were set at the same placein the experimental setup. All measurements were carried out atroom temperature.

III. RESULTS AND DISCUSSIONS

A. Absorption Spectra and Judd−Ofelt Analysis. Theabsorption spectra of Er3+/Nd3+-codoped fluorotellurite glassesare shown in Figure 1 and the spectra of all samples are similar;no shifts of the wavelength was found in the absorption peaks.The absorptions bands belong to the transition of Er3+ andNd3+ ions from the ground state to the labeled levels are shownin Figure 1. The strong absorption at around 808 nm indicatesthat these glasses can be excited quite efficiently by a

conventional 808 nm laser diode (LD) because of the overlapof Er3+: 4I15/2 → 4I11/2 and Nd3+: 4I9/2 → 4F5/2,

2H9/2transitions.The radiative transition within the 4fn configuration of a rare

earth ion can be analyzed by Judd−Ofelt theory.13 The Judd−Ofelt parameters were obtained from the measured absorptionspectra excluding the absorption from the ground state 4I15/2 tothe 4I13/2 level. According to previous studies, the value of Ω2 isrelated with the symmetry of the glass while the value of Ω6 isinversely proportional to the covalency of Er−O bond.Additionally, the values of Ω4 and Ω6 are related to the PHvalue of host materials. The larger the PH value, the lower thevalues of Ω4 and Ω6. The value of Ω4/Ω6 is an importantparameter to predict the excited emission in a laser active host.8

The larger the Ω4/Ω6 favors, the more desired the lasertransition. The Ωt parameters, the spontaneous emissionprobabilities (A), branching ratios (β), and calculated radiativelifetime for 4I13/2 and 4I11/2 are listed in Table 1. With thepresence of F ions, the values of Ωt (t = 2, 4, 6) are increased.It is possible to infer that the covalency of Er−O is decreasedand the PH value of host material is decreased by the presenceof fluorine ions. With the increase of fluorine ions, the values ofΩ4/Ω6 were increased which hints the enhanced 2.7 μmemission. According to the Judd−Ofelt theory, the line strengthof the electric dipole components (Sed) of 2.7 μm emission canbe calculated as

→

= ⟨|| ||⟩ × Ω + ⟨|| ||⟩Ω + ⟨|| ||⟩

× Ω

= Ω + Ω + Ω

S

U U U

(4I I )

0.021 0.11 1.04

ed 11/24

13/2

(2)2

(4)4

(6)

6

2 4 6 (1)

which is a function of glass structure and composition.14 It canbe found that large Ωt will produce a large Sed value. And thelarge Sed indicates increased electric-dipole transition whichbrings to flat emission spectra.In addition, with the increase of fluorine ions, the calculated

values of τ(4I11/2) and τ(4I13/2) increased. However, accordingto the energy transfer processes prescribed in previousresearches, the values of τ(4I13/2) were quenched greatly bythe presence of Nd3+ ions.4,5,8 The experimental values ofτ(4I13/2) of Er3+/Nd3+-codoped fluorotellurite glasses wereabout 400 μs (shown in Figure 2). The energy transferefficiency ηt of Er3+:4I13/2 + Nd3+:4I9/2 → Er3+:4I15/2 +Nd3+:4I15/2 transition can be evaluated from the lifetime valuesby the following equation:9

ητ

τ= −1t

Er/Nd

Er (2)

Here τEr/Nd and τEr are the lifetimes of the Er3+:4I13/2 level with

and without Nd3+ ions, respectively. The value of ηt is up to81.5%. The slight decrease of ηt could be attributed to theimpact of the variation of refractive index and the densitycaused by the increased fluorine ions. The high ηt demonstratesthat Nd3+ ions can efficiently quench the lower level of Er3+

ions for 2.7 μm emissions.B. Physical Properties. The thermal stability was

characterized by the value of ΔT (Tx− Tg), where Tg is theglass transition temperature and Tx is the onset crystallizationtemperature. A high Tg gives glass good thermal stability toresist thermal damage at high pumping intensity. ΔT presents

Figure 1. Absorption spectra of Er3+/Nd3+-codoped fluorotelluriteglasses.

The Journal of Physical Chemistry A Article

dx.doi.org/10.1021/jp301582b | J. Phys. Chem. A 2012, 116, 5571−55765572

the temperature interval during the nucleation and higher valueof ΔT indicates the potential for fiber fabrication withoutcrystallization. Hruby’s parameter KH = (Tc − Tg)/(Tm − Tc)evaluates glass forming ability, where Tc is the crystallizationtemperature and Tm is the melting temperature.13 According tothis Hruby’s equation, the larger KH is, the stronger inhibitionto nucleation and crystallization processes is, and consequently,the better glass forming ability is.The refractive index (n), density (ρ), characteristic temper-

atures and thermal parameters of fluorotellurite glasses werelisted in the Table 2. It is clear from Table 2 that the values of ndecrease while the values of ρ increase with the increase offluorine ions. The n of glasses is related with the polarization inglasses. The lower the polarization, the lower the value of n.

Because the polarization of fluorine ions (F) is much lowerthan that of oxygen ions (O2), the n decreases with theincrease of fluorine ions concentration. In Table 2, except theTF2 sample, the fluorotellurite glasses maintain the goodthermal stability. For the 60TeO2−15GeO2−(20−x)ZnO−xZnF2−(5−y)K2O−yKF glasses, the ΔT and KH are consid-erable with 60TeO2−15GeO2−20ZnO−5K2O glass. The valueof ΔT approaches to 176 in TF3 sample indicating that thethermal stability against crystallization is good. Additionally,large ΔT indicates a wide working-temperature range for highquality fiber drawing.Figure 3 shows the Raman spectra of fluorotellurite glasses.

All the spectra were normalized by the intensities of 820 cm−1

and a least-squares fit was made for the Raman spectra of TF1sample, assuming a Gaussian shape for each Raman band. Ascan be seen from Figure 3a, six individual modes aredistinguished for all the glasses: five medium peaks around129, 172, 293, 443, and 677 cm−1 and one strong peak around767 cm−1. And it is clear in Figure 3b that the peaks do not shiftwith the increase of fluorine ions. It is well-known that Ramanpeaks around 725−780 and 305 cm−1 are attribute to the[TeO3] groups and these around 650−670 and 455 cm−1 areattribute to the [TeO4] groups in tellurite glasses. The fluorineions replace bridging-oxygen (BO) ions in the [TeO3] and[TeO4] groups and these groups convert to [Te(O, F)3] and[Te(O, F)4] groups with bridging-fluorine (BF).

15 The networkstructures are composed of the mixed [Te(O, F)3] and [Te(O,F)4] groups in fluorotellurite glasses. It can be concluded thatthe peaks around 767 and 293 cm−1 are assigned to the [Te(O,F)3] groups and the peaks around 677 and 443 cm−1 areassigned to the [Te(O, F)4] groups in Figure 1a. Because of thestronger heteropolar bond strength of fluorine ions than oxygenions, the BF bond will stabilize the chain structure while two

Table 1. Judd−Ofelt Intensity Parameters of Er3+ Ions, the Branching Ratio, the Spontaneous Emission Probabilities,Calculated Radiative Lifetime for 4I13/2 and

4I11/2 Levels, and Measured Lifetime of 4I13/2 Level in Er3+-Doped and Er3+/Nd3+-Codoped Fluorotellurite Glasses

parameters TE TF1 TF2 TF3 TF4 TF5 TF6

Ω2 (×10−20 cm2) 4.38 8.32 7.65 7.66 7.26 7.74 7.79

Ω4 (×10−20 cm2) 3.05 4.19 3.48 3.44 3.74 3.58 3.94

Ω6 (×10−20 cm2) 1.04 2.43 1.44 1.55 1.38 1.48 1.72

Ω4/Ω6 2.93 1.72 2.41 2.22 2.71 2.42 2.29δ (×10−6) 0.46 0.16 0.81 0.73 0.59 1.03 1.1Sed(

4I11/2 →4I13/2) 1.51 3.16 2.04 2.15 2.00 2.10 2.38

A(4I11/2 →4I13/2) (s

−1) 50.02 88.04 64.31 63.56 64.31 58.95 64.81β(4I11/2 →

4I13/2) (%) 18.36 14.21 15.66 15.44 15.66 15.72 15.35A*β(4I11/2 →

4I13/2) 918 1251 1007 981 1007 927 995τ(4I11/2) (calculated) (ms) 3.67 1.61 2.44 2.43 2.44 2.67 2.37τ(4I13/2) (calculated) (ms) 3.95 2.04 2.96 2.97 2.96 3.23 2.89τ(4I13/2) (experimental) (μs) 1.76 (ms) 325 365 411 419 443 450ηt (%) 81.5 79.3 76.6 76.2 74.8 74.4

Figure 2. Luminescence decay curve of 1535 nm emission in Er3+/Nd3+-codoped fluorotellurite glasses.

Table 2. Refractive Index, Density, Characteristic Temperatures, and Thermal Parameters of Fluorotellurite Glasses

samples n (λ = 633 nm) ρ (g/cm3) N (1020 cm−3) Tg (°C) Tx (°C) Tc (°C) ΔT (°C) KH

TE 1.8875 4.730 4.229 421 561 590 140 0.302TF1 1.9198 4.7302 4.198 372 540 577 168 0.358TF2 1.9206 4.8664 4.377 338 443 462 105 0.180TF3 1.8939 4.8972 4.368 386 562 582 176 0.345TF4 1.8707 4.8273 4.271 388 559 587 171 0.353TF5 1.8718 4.7862 4.270 384 532 570 148 0.320TF6 1.8639 4.8047 4.184 381 531 558 150 0.299



[Te(O, F)4] groups are connected by the BF bond. It can befound that all the peaks decrease in intensity as the fluorine ionsincrease, especially the peak around 767 cm−1. The mixedfluorine and oxygen anions are presented in this fluorotelluriteglasses system, and the vibration strength of symmetry ligandfield decreases as increasing fluorine ions. With the increasedconcentration of fluorine ions, the ratio of [Te(O, F)4] groupsto the [Te(O, F)3] and [Te(O, F)4] groups increases and thestability in these glasses becomes better, as evidenced by thechanges in characteristic temperatures.With conventional melting processes, the glasses containing

little OH groups cannot be prepared without an elaboratesetup. A simple way of removing the OH groups from theglass during melting process is to add a fluoride to liberatehydrogen species from the melt.15 The added fluorine ions willreact with OH groups according to eq 3:16

− +

→ − − + + ↑

−

−

2[ Te OH] 2F

Te O Te O 2HF(g)2(3)

The vibration of OH groups (2700−3700 cm−1) matcheswith the energy gap between the Er:4I11/2 →

4I13/2 transition(about 3650 cm−1). The introducing fluorine ions deplete theOH groups which participates in the energy transfer (ET) ofrare-earth ions. The upper level (Er3+:4I11/2) could transfer tothe lower level (Er3+:4I13/2) by nonradiative transition easilywith the assistance of OH groups.9,17 The content of OH

groups in the glass can be evaluated by the absorptioncoefficient αOH of the OH vibration band at 3 μm (listed inTable 3), which can be given by

α = T T lln( / )/OH 0 (4)

Figure 3. Peak deconvolution of the Raman spectra of TF1 sample (a); Raman spectra of Er3+/Nd3+-codoped fluorotellurite glasses (b).

Table 3. Absorption Coefficient αH of Er3+-Doped and Er3+/Nd3+-Codoped Fluorotellurite Glasses

sample TE TF1 TF2 TF3 TF4 TF5 TF6

αOH (cm−1) 0.990 0.466 0.544 0.291 0.204 0.181 0.196

Figure 4. Mid-infrared transmittance: the trends of (a) the highest and (b) the lowest transmittance of Er3+/Nd3+-codoped fluorotellurite glasses.



where l is the thickness of the sample equal to 2 mm, and theT0 and T are the incident and transmitted transmittanceintensities, respectively. The mid-infrared transmittance spectra,the highest transmittance (around 2730 nm) and the lowesttransmittance (around 3100 nm) of fluorotellurite glasses areshown in Figure 4 and the value of αOH is shown in Table 3. Itcan be found that TF5 sample has the highest maximumtransmittance (approach to 80%). As shown in Figure 4, thetransmittance of glass decreases with a small amountintroduction of fluorine ions and it increases clearly with theincrease of fluorine ions. It can be demonstrated by the effect ofintroduced fluorine ion on the structure of glass: a smallamount introduction of fluorine ions will destroy the stable-structure of tellurite glass and the equilibrium between fluorineand oxygen ions were achieve with the increase of fluorine ions.Then, the glasses’ structure tends to be much more stable andhomogeneous, which is registered as better thermal stabilityand transmission and which matches with the variation of[Te(O, F)4] groups. It can be deduced from Table 3 that theintroduced fluorine ions can eliminate the OH content andThe TF5 sample possesses the lowest αOH in all samples. Theexcellent properties hints that the TF5 sample might possessesbetter emission properties especially 2.7 μm emission.C. Radiative Properties. Generally, considering the

nonradiative processes, the total rate (1/τmea) of the 4I11/2 →4I13/2 transition can be evaluated by the reciprocal of themeasured fluorescence lifetime (τmea) which is given by

τ= + + +W W W W

1

meaR CR ET MPR

(5)

where WR is the radiative transition rate obtained from Judd−Ofelt theory (the spontaneous emission probability A); WCR isthe rate of cross-relaxation, and WET and WMPR are the rate of

energy transfer to impurities (i.e., OH) and multiphononrelaxation, respectively. Since the rare earth concentrations inpresent glasses do not change clearly with the increase offluoride ions, theWCR of each sample can be thought of roughlyequal. The WET is proportional to the concentration of Er3+

ions (NEr) and the measured content of OH groups (αOH)which can be defined as18,19

α= = −W W K NET OH OH Er Er OH (6)

where KOH‑Er is a constant which is determined by interactionsbetween Er3+ ions and OH groups and is independent of theconcentrations of Er3+ ions and OH groups. The KOH‑Er is 14× 10−19 cm4·s−1 in tellurite glasses. The multiphonon relaxationrate WMPR is a function of temperature, which can be expressedas

= −

= −α

−ℏ −

− Δ −ℏ −

W T W e

Ce e

( ) (0)[1 ]

[1 ]MPR MPR

w kT p

E w kT p

/

/

max

max (7)

where C and α are positive-definite constants related to thehost materials, and ΔE is the energy gap between the 4I11/2 and4I13/2 levels. The values of C and α in tellurite glasses have beendetermined previously to be C = 4.2 × 107 s−1 and α = 4.5 ×10−3 cm.20 The ℏwmax is the highest phonon energy obtainedfrom Raman spectra and p=ΔE/ℏwmax. The calculated WR,WET, WMPR, and 1/τmea are listed in Table 4. It is found that thevalue of WET decreases greatly with the increase of fluorine ionconcentration and the TF5 sample possesses the lowest value ofWET. As the radiatively low value of WMPR and WR, the value of1/τmea is greatly influenced by the changes of WET. Therefore, itcan be concluded that the trends of 2.7 μm emission is similarto that of the transmission around 3.0 μm.

D. Optical Spectra. The 1.5 and 2.7 μm emission spectra ofEr3+-doped tellurite glass and Er3+/Nd3+-codoped fluorotellur-

Table 4. Calculated Rates of Radiative Transition (WR), Energy Transfer (WET), and Multiphonon Relaxation (WMPR) and theCalculated Total Rates (1/τmea) in Er3+-Doped Tellurite Glass and Er3+/Nd3+-Codoped Fluorotellurite Glasses

sample TE TF1 TF2 TF3 TF4 TF5 TF6

WR (s−1) 50.02 88.04 64.31 63.56 64.31 58.95 64.81WET (s−1) 586.1 273.9 333.3 178.0 121.9 108.3 114.8WMPR (s−1) 3.477 3.477 3.477 3.477 3.477 3.477 3.4771/τmea (s

−1) 640.2 365.4 401.1 245.0 189.7 170.7 183.1

Figure 5. 1.5 μm (a) and 2.7 μm emission (b) spectra of Er3+-doped tellurite glass and Er3+/Nd3+-codoped fluorotellurite glasses.



ite glasses are shown in Figure 5. It is found that the 1.5 μmemission is considerably quenched and the 2.7 μm emission isconsiderably enhanced by the presence of Nd3+ ions. It is alsofound that the TF5 sample presented the highest 2.7 μmemission and the variation tendency of 1.5 and 2.7 μm emissionare similar. According to the energy transfer mechanismelaborated in previous papers,4,8 there is a closed correlationbetween the 1.5 and 2.7 μm emission. The 4I13/2 level, which isthe lower level of and the upper level of 1.5 μm emission, is oneof main factors influencing the property of 2.7 μm emission.Under the same energy transfer mechanism, high 2.7 μmemission will lead to high 1.5 μm emission. Therefore, thevariation tendency of 1.5 μm emission is similar to that of 2.7μm emission with the increase of fluorine ions concentration.On the basis of the analysis of radiative properties, the 2.7 μmemission is closely associated with the transmission around 3.0μm, which is related to the content of OH groups. It can beconcluded that the added fluorine ions affect the 2.7 μmemission greatly by reducing the content of OH groups.

IV. CONCLUSIONGenerally, the physical and optical properties of Er3+/Nd3+-codoped fluorotellurite glasses were investigated, especially the2.7 μm emission. On the basis of the absorption spectra, theJudd−Ofelt and radiative parameters were calculated. Accord-ing to the analysis of Raman spectra, the phonon energy offluorotellurite glasses did not change and the glass-networkstructures of fluorotellurite glasses were composed of [Te(O,F)3] and [Te(O, F)4] groups which gives the evidence ofchanges of thermal properties. With the increase of fluorineions, the content of OH groups decreased as well as thevalues of WET decreased. The value of 1/τmea, which is greatlyaffected by the value of WET, is an important factor for 2.7 μmemission. As a result, the 2.7 μm emission is greatly enhancedby the presence of fluorine ions and the TF5 sample possessesthe strongest 2.7 μm emission while the molar concentration ofZnF2 is 15%. The improved thermal, raditive and 2.7 μmemission properties in fluorotellurite glasses indicates that thepresence of fluorine ions is good for 2.7 μm emission and theEr3+/Nd3+-codoped fluorotellurite glasses is promising for mid-infrared laser devices.

■ AUTHOR INFORMATION

Corresponding Author*Telephone: +86 21 5991 4297. Fax: +86 21 5991 4516. E-mail: [email protected].

NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTSThis work is financially supported by the National NaturalScience Foundation of China (No. 51172252).

■ REFERENCES(1) M. Frenz, H. P.; Konz, F.; Jansen, E. D.; Welch, A. J.; Weber, H.P. IEEE J. Quantum Electron. 1996, 32, 2 025−2 036.(2) Hibst, R. Lasers Surg. Med. 1992, 12, 125−130.(3) Kaufmann, R.; Hibst, R. Clin. Exp. Dermatol. 1990, 15, 389−393.(4) Guo, Y.; Li, M.; Tian, Y.; Xu, R.; Hu, L.; Zhang, J. J. Appl. Phys.2011, 110 (031), 512−5.(5) Lin, H.; Chen, D.; Yu, Y.; Yang, A.; Wang, Y. Opt. Lett. 2011, 36,1 815−1 817.

(6) Zhu, X.; Peyghambarian, N. Adv. OptoElectron. 2010 2010, 501,956−23.(7) Moizan, V.; Nazabal, V.; Troles, J.; Houizot, P.; Adam, J. L.;Doualan, J. L.; Moncorge, R.; Smektala, F.; Gadret, G.; Pitois, S.; et al.Opt. Mater. 2008, 31, 39−46.(8) Zhong, H.; Chen, B.; Ren, G.; Cheng, L.; Yao, L.; Sun, J. J. Appl.Phys. 2009, 106 (083), 114−3.(9) Xu, R.; Tian, Y.; Hu, L.; Zhang, J. Opt. Lett. 2011, 36, 1 173−1175.(10) Tian, Y.; Xu, R.; Zhang, L.; Hu, L.; Zhang, J. Opt. Lett. 2011, 36,109−111.(11) Wang, G.; Dai, S.; Zhang, J.; Xu, S.; Hu, L.; Jiang, Z. J. Non-Cryst. Solids 2005, 351, 2147−2151.(12) Nazabal, V.; Todoroki, S.; Nukui, A.; Matsumoto, T.; Suehara,S.; Hondo, T.; Araki, T.; Inoue, S.; Rivero, C.; Cardinal, T. J. Non-Cryst. Solids 2003, 325, 85−102.(13) Gao, G.; Hu, L.; Fan, H.; Wang, G.; Li, K.; Feng, S.; Fan, S.;Chen, H.; Pan, J.; Zhang, J. Opt. Mater. 2009, 32, 402−405.(14) Tian, Y.; Xu, R.; Hu, L.; Zhang, J. Opt. Mater. 2011, 34, 308−312.(15) Zhang, J.; Qiu, J.; Kawamoto, Y. Mater. Lett. 2002, 55, 77−82.(16) ODonnell, M. D.; Miller, C. A.; Furniss, D.; Tikhomirov, V. K.;Seddon, A. B. J. Non-Cryst. Solids 2003, 331, 48−57.(17) Sun, J.; Nie, Q.; Dai, S.; Gang, L.; Song, B.; Chen, F.; Wang, G.;Xu, T. J. Inorg. Mater. 2011, 26, 836−840.(18) Dai, S.; Yu, C.; Zhou, G.; Zhang, J.; Wang, G. J. Non-Cryst. Solids2008, 354, 1 357−1 360.(19) Jacinto, C.; Oliveira, S. L.; Nunes, L. A.; Catunda, T.; Bell, M. J.J. Appl. Phys. 2006, 100 (113), 103−6.(20) van Dijk, J. M. F.; Schuurmans, M. F. H. J. Chem. Phys. 1983, 78,5 317−5 323.



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effect of fluorine ions on 2.7 μm emission in er 3+ /nd ...

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