Abstract

In this paper, we present the luminescent properties of Tm3+/Ho3+ co-doped new glass. A series of silicate-germanate glass was prepared by the conventional melt-quenching method. In the Tm3+/Ho3+ co-doped silicate-germanate glass, a strong emission of 2 μm originating from the Ho3+:I75I85 transition can be observed under conventional 808 nm pumping. The characteristic temperatures, structure, and absorption spectra have been measured. The radiative properties of Ho3+ in the prepared glass were calculated. The emission cross section of Ho3+ ions transition can reach 4.78×1021  cm2 around 2 μm, and the FWHM is as high as 153 nm. The energy transfer efficiency between Ho3+ and Tm3+ has a large value (52%), which indicates the Tm3+/Ho3+ co-doped silicate-germanate glass is a suitable candidate for the 2 μm laser. Moreover, the energy transfer mechanism between Tm3+ and Ho3+ ions was investigated.

© 2016 Chinese Laser Press

1. INTRODUCTION

During the last few decades, the development of solid state lasers generating 2 μm emission has been gaining much attention because of its important applications, such as biomedical uses, mid-infrared remote sensing, monitoring of atmosphere pollutants, eye-safe laser radar, and high-resolution spectroscopy of low-pressure gasses [13]. Until now, researchers have made progress in mid-infrared luminescence materials mainly focusing on rare-earth-doped glasses [4,5] and bismuth-doped glasses [6,7]. In order to get a powerful 2 μm laser, it is known that the appropriate selection of rare-earth ions and matrices are important for rare-earth-doped glasses. Ho3+ ion can generate a 2 μm laser through transition of Ho3+:I75I85, which has been demonstrated in many glass matrices [2,8] until now. However, owing to the absence of a well-matched absorption band, Ho3+ cannot directly be pumped by the commercially available 808 or 980 nm laser diode (LD) in single-doped Ho3+ systems. In this respect, Tm3+, Er3+, or Yb3+ ions were widely added into Ho3+-doped glasses as a sensitizer to achieve 2 μm emission [2,8,9]. Compared with Yb3+ and Er3+, Tm3+ ions often act as a sensitizer when co-doped with Ho3+ ions because the energy gap between Tm3+:F43H63 matches with that of Ho3+:I85I75. Thus, pump energy can be absorbed by Tm3+ effectively and ensuing efficient energy transition from F43 of Tm3+ to Ho3+:I75 under 800 nm LD pumping. Thus, Ho3+ can be co-doped with Tm3+ ion as a sensitizer, which is a suitable way to achieve 2 μm emission and can be pumped in the wavelength range of commercial LDs.

To obtain a high-efficient mid-infrared emission, host material is another important factor that should be taken into consideration. Up to now, crystals and glasses have been investigated for a 2 μm laser [1012]. Generally, glasses have the advantage of lower cost and shorter preparation period than those of the crystals [13]. Recent decades have witnessed the development of various Tm3+/Ho3+ co-doped glass hosts, including bismuthate glass [9], tellurite glass [14], silicate glass [15], and germanate glass [16] pumped by the common 808 nm LD. To our knowledge, there are some investigations on Er3+/Ho3+-co-doped germanosilicate glass [17], and other investigations were on upconversion luminescence [18]. However, to the best of our knowledge, few researchers have reported on Tm3+/Ho3+ double-doped silicate-germanate glass for Raman spectra and 2 μm emission. Silicate-germanate glass combines the advantage of low cost, stable chemical properties of silicate glasses and good thermal stability, relatively low phonon energy together with high infrared transmissivity of germanate glass [19,20]. According to previous reports, we can observe that the vibrational strength of Si-O bonding becomes weaker, and silicate-germanate glass possesses moderate phonon energy due to GeO2 in substitution for SiO2 [21]. Therefore, the present paper proposes silicate-germanate glass as the host material.

To the best of our knowledge, there are few studies on Raman spectra, and 2 μm emissions in Tm3+/Ho3+ co-doped silicate-germanate glasses have been reported. In the present study, the Raman spectrum in Tm3+/Ho3+ co-doped silicate-germanate glass has been investigated. The spectroscopic properties of the silicate-germanate glasses were presented and investigated systematically. According to the Judd–Ofelt (J-O) theory and absorption spectra, J-O parameters, radiative transition probabilities, branching ratios, and lifetimes of Ho3+ were calculated in silicate-germanate glass. Furthermore, the related energy-transfer mechanisms among excited states and micro-parameters of the energy transfer processes also were quantitatively analyzed.

2. EXPERIMENTAL

A. Material Synthesis

The molar composition of rare-earth-ions un-doped samples are named SG and S0. Additionally, the investigated glass compositions are shown in Table 1. All the samples were prepared by the conventional melt-quenching method with high purity reagents in powder form. Batches of the samples (20 g) were completely mixed. Then, the samples were placed in a platinum crucible and melted at 1450°C for 30 min until bubble-free liquid was formed. Then, the melts were swirled to ensure homogeneity and subsequently poured on a preheated copper mold and annealed at 550°C for 2 h to remove the internal stresses before they were cooled to room temperature with a muffle furnace. The annealed glass samples have smooth morphology; further, the prepared samples were cut and polished to the size of 10  mm×10  mm×1.5  mm for measuring their optical and spectroscopic properties, whereas others were cut and polished for recording refractive index.

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Table 1. Compositions of the Prepared Glasses

B. Measurements

The density of the samples was measured using Archimedes’ water-immersion method on an analytical balance. Refractive index was measured at room temperature by the prism minimum deviation method. The characteristic temperatures (temperature of glass transition Tg and onset crystallization peak Tx) were tested by a differential scanning calorimeter (DSC). Absorption spectra were recorded at room temperature in the wavelength range of 350–2200 nm with a Perkin Elmer Lambda 900UV-VIS-NIR spectrophotometer. The Raman spectrum of glass sample was measured with an FT Raman spectrophotometer (Nicolet MODULE) in the spectral range of 601100  cm1, which has a resolution of 4  cm1. The fluorescence spectra were measured with a computer-controlled Triax 320 type spectrometer upon excitation at 808 nm. The fluorescence lifetimes of F43 level were recorded with an HP546800B 100-MHz digital oscilloscope and pumped by 800 nm LD. All the measurements were done at room temperature.

3. RESULTS AND DISCUSSION

A. Physical and Thermal Property

The physical and thermal property results of the analyzed glasses are listed in Table 2. For the investigated samples from Table 2, the density of the germanium-oxide-free sample is found to be 3.16  g/cm3. Subsequently, it is observed that the density increased after introducing GeO2 into the glass contents. The reason for increment in density is due to the large molecular weight M of GeO2. Additionally, the refractive index for the studied compositions also increased with increasing GeO2 contents. The present silicate-germanate glasses have a high refractive index (n=1.70) compared with fluorophosphate (n=1.56) [8] or silicate (n=1.48) glasses [22]. The rare-earth-ions’ electric dipole transition rate Arad increases with the increase of refractive index according to Arad(n2+2)2/n. Thus a higher value of the refractive index (n) increases the spontaneous emission probability (Arad) and consequently provides a better opportunity to obtain laser actions in the laser medium.

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Table 2. Physical and Thermal Properties of Silicate-Germanate Glasses

At the same time, Table 2 shows the characteristic temperatures (containing temperatures of glass transition Tg and onset crystallization Tx) of the prepared host glass. From Table 2, it can be seen that the present silicate-germanate glass possesses a larger Tg value compared with germanate (596°C) [23] and fluorogallate (640°C) glass [24]. According to previous reports, glass hosts have a high Tg value, which can make it achieve good thermal stability to resist thermal damage at high pumping power [25]. The difference between Tg and Tx(ΔT=TxTg) [26] of glass is also given in Table 2. Generally, it is desired that ΔT is as large as possible to achieve a wide range of working temperature during the fiber fabricating. Because fiber fabricating is a reheating process, any crystallization during the process will affect the optical properties [27]. The larger ΔT is, the better thermal stability the glasses will have [28]. According to Table 2, the ΔT of silicate-germanate glass is 155°C, which is significantly higher than that of germanate (111°C) [23] and fluoride (90°C) glass [29]. Thus, the results show that the Tm3+/Ho3+ co-doped silicate-germanate glass has good thermal stability, which is helpful for the construction of optical fibers.

B. Raman Spectrum

In the last decades, the structure of niobium silicate glasses [30,31] and alkali germanaosilicate glasses [32] has been reported by the Raman spectroscopic technique. However, few papers, to the best of our knowledge, have reported on the Raman spectra of niobium silicate-germanate glass. Figure 1 presents the vibrational spectra of an investigated silicate-germanate glass sample. It can be seen that the maximum phonon energy of the present sample is located at 804  cm1, which is lower than that of sodium germanosilicate glass (862  cm1) [33]. For the sake of detailed analysis, the Gaussian deconvolution procedure is utilized to fit multipeaks [34], and the result is showed in Fig. 1. It can be found that the bands of five peaks are around at 325, 552, 784, 804, and 973  cm1. According to the reported literatures, the low frequency region at around 325  cm1 is related to the chains of GeO4 tetrahedra connected by six coordinated Ge units within the network [32]. Meanwhile, the weak peak at around 552  cm1 was observed, which has been attributed to the presence of germania, related to the Ge-O-Nb bonds, a structural network formed by GeO4 tetrahedra and NbO6 octahedra according to [35,36]. In the high-frequency region, the band at 784  cm1 is assigned to NbO6 octahedra [36]. The latter intensity band centered near 804  cm1 should be assigned to the Nb-O bonds because, as the polarizability of Nb-O bonds is higher than that of Si-O bonds on the Raman spectra, the bands related to Si-O vibrations usually cannot be seen [31]. Compared with the structure of SiO2 glass [37] and the alkali germanate compositions [32], the new shoulder is observed at 973  cm1 in the silicate-germanate glass, which should be related to the vibrational modes of Ge-O-Si linkages [35].

 

Fig. 1. Deconvolution of Raman spectrum of SG glass using symmetric Gaussian functions.

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C. Absorption Spectra

In order to better understand the properties of glass, some important optical parameters were calculated for our samples. Figure 2 shows optical absorption spectra of Tm3+ single doped, and Tm3+/Ho3+ co-doped silicate-germanate glasses at room temperature in the wavelength range from 400 to 2200 nm. The length of samples is 10 mm for the measurement of the absorption spectra. The spectra shapes of single-doped or co-doped glass samples are similar, and the absorption intensity is proportional to the mol content of Tm3+ and Ho3+ ions.

 

Fig. 2. Absorption spectra of Tm3+ single-doped and Tm3+/Ho3+ co-doped silicate-germanate glasses in the range of 400–2200 nm.

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From the absorption spectra, several inhomogeneously broadened absorption peaks can be observed, which are assigned to the transition from the ground-state level to the excited states of 4f configuration of Tm3+ and Ho3+ ions, respectively. Some important absorption bands are labeled in the spectra. It can be seen that the 808 or 980 nm LD is not applicable to Ho3+ ions. Nevertheless, levels H43 of the Tm3+ ions can be excited at 808 nm. The intense absorption band centered at nearly 800 nm of the Tm3+/Ho3+ co-doped sample from absorption curve, which indicates Tm3+ can function as an absorber to increase the absorption of the 808 nm pumping energy. Additionally, in comparison to single-doped and co-doped glass samples, it can be found that the shape and peak positions of each transition are similar, and there is no shift of the absorption peaks. This result indicates that there is no apparent cluster in the local ligand field, and both Ho3+ and Tm3+ ions are homogeneously incorporated into the glassy network. Meanwhile, Figure 2 shows the absorption peak intensity with Tm3+ ions at different concentrations, in which a significant increase of absorption with increased Tm3+ ions concentrations is clearly observed when concentrations of Ho2O3 remained constant.

D. J-O Analysis and Radiative Properties

To the best of our knowledge, J-O theory [38,39] has been often used to discuss the radiative properties of rare-earth ions within the host matrix from the absorption spectra. According to J-O theory, the J-O intensity parameters Ω2, Ω4, and Ω6 for 4f–4f transitions of Ho3+ ions in the glass samples were computed from the measured absorption spectra. Afterward, these parameters Ωt (t=2, 4, 6) were used to evaluate radiative properties of the main laser emitting levels of Ho3+ in silicate-germanate glass, such as radiative transition probability (Arad), fluorescence branching ratios (β), and radiative lifetime (τrad). The parameters Ωλ are important for the investigation of the local structure and bonding in the vicinity of rare-earth ions. The J-O intensity parameters of glass in this paper are compared with those obtained from various other Ho3+ doped glasses, as listed in Table 3. It should be noted that the five absorption bands—I65, F55, F45+S25, F15+G65, and G55—were used for the calculation in this process because the transition I85I75 has a substantial magnetic dipole component. From Table 3, it is observed that the oxide glasses have large Ω2 and small Ω6 values. The Ω2 parameter of silicate-germanate glass follows the trend Ω2>Ω4>Ω6. This trend is consistent with the one observed for other glasses, such as silicate, germanate, fluorophosphate, and phosphate glasses; however, it differs from those of fluoride and tellurite glasses, as shown in Table 3. The root mean square deviation δrms was calculated to be 1.31×106. According to previous studies, Ω2 is related with some factors such as the ligand symmetry of host glass, the degree of covalency of the chemical bonds between rare-earth ions and its nearest neighbor atoms of a glass. Ω4 and Ω6 are related to the covalency of the medium in which the rare-earth ions are situated. And Ω6 reflect the bulk properties of the host such as rigidity and viscosity [8], which can be adjusted by the composition or structure of the glass host. It is also found that Ω2 for Ho3+ in this work is larger than that of silicate [40], fluoride [41], fluorophosphate [42], tellurite [14], and phosphate [40] glass hosts. A large Ω2 value is probably due to relatively high covalency of the chemical bond between rare-earth and oxygen ions. But the value of Ω2 is smaller than that in germanate [43] glass. Thus the result indicates that ligand asymmetry around the rare-earth ions in Tm3+/Ho3+ co-doped germanate glass is stronger than those in silicate-germanate glass. The smaller the Ω6 value is, the stronger covalence between anions and rare-earth ions. It can be seen clearly that the Ω6 of studied glass is smaller than that of various other glasses, as shown in Table 3. The J-O analysis indicated a strong asymmetry and covalent environment between the rare-earth ions and the ligand in the present matrix.

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Table 3. J-O intensity Parameters (Ωλ, λ=2, 4, 6) (×1020  cm2) of Ho3+ Ions in Various Glass Hosts

Furthermore, the spontaneous transition properties of the Ho3+ are shown in Table 4, including the spontaneous transition probability Arad, branching ratio β, and radiative lifetime τrad of different emission states of Ho3+ ions in silicate-germanate glass, which were evaluated using the three intensity parameters through J-O theory. Table 4 shows that the values of Arad for the Ho3+:I75I85 transition and τrad of the I75 level of Ho3+ are 103.46  s1 and 9.67 ms, respectively. The Arad value is larger than that of germanate, phosphate [41], silicate [44], and fluorophosphates [45] glasses. Higher Arad is beneficial in achieving intense infrared emissions. Consequently, this silicate-germanate glass can be considered as an appropriate host glass to achieve 2 μm laser from the Ho3+:I75I85 transition.

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Table 4. Spontaneous Transition Probability Arad, Branching Ratio β, and Radiative Lifetime τrad for Different Excited Levels of Ho3+ in Silicate-Germanate Glass

E. Fluorescence Spectra

Figure 3 shows Tm3+/Ho3+ co-doped silicate-germanate glass fluorescence spectra in the range of 1600–2200 nm when excited by 808 nm LD at room temperature. From Fig. 3, it can be seen clearly that two emission peaks are centered near at 1.8 and 2 μm, which correspond to the Tm3+:F43H63 and Ho3+:I75I85 transition, respectively. Moreover, the 1.8 and 2 μm fluorescent intensity is in direct proportion to the Tm2O3 concentration, while, compared with the 2 μm emission, the emission intensity of 1.8 μm increased relatively little. Due to the intense energy transferring (ET) between the F43 state of Tm3+ and Ho3+:I75 state and cross-relaxation (CR) of adjacent Tm3+ ions.

 

Fig. 3. Fluorescence spectra of the Tm3+/Ho3+ co-doped silicate-germanate glasses.

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In order to explain the mechanism of strong 2 μm luminescence, Fig. 4 shows the simplified energy level diagrams of Tm3+ and Ho3+ ions identified from the absorption spectra. The locations of the energy levels are similar to those reported previously for bismuthate [9] and tellurite [11] glass hosts. And the detailed energy transfer paths between the two rare-earth ions can be illustrated. In Fig. 4, the start state H63 of Ho3+ ions are initially excited to the excited state of the Ho3+:F43 level when Tm3+/Ho3+ co-doped glass is pumped by 808 nm LD. Afterward, part of the ions of Tm3+ in the H43 state drop down to the F43 state, then the Tm3+:F43 level decays to the H63 level emitting 1.8 μm fluorescence. While most of the excited Tm3+ ions in H43 states are excited from the H63 ground state to F43 state via CR between Tm3+:H43 level and Tm3+:H63 level and multiphonon relaxation (MR) process. Tm3+ ions in the F43 state transfer energy to the Ho3+ ions in I75 state via the ET process. After that, once the Ho3+:I75 state is populated, the 2 μm emission via Ho3+:I75I85 transition takes place. The detail transfer mechanism is described as follows:

H63(Tm3+)+hv(808  nm)H43(Tm3+)  (GSA)H43(Tm3+)+H63(Tm3+)F43(Tm3+)+F43(Tm3+)  (CR)F43(Tm3+)H63(Tm3+)+hv(1.8  μm)  (emission)F43(Tm3+)+I85(Ho3+)H63(Tm3+)+I75(Ho3+)  (ET)I75(Ho3+)I85(Ho3+)+hv(2  μm)  (emission)

 

Fig. 4. Energy level diagrams and energy transfer sketch map of Tm3+ and Ho3+ ions.

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F. Absorption and Emission Cross Sections

The absorption and emission cross sections are two vital spectroscopic parameters and related to the optical gain of a laser material. The emission cross section (σem) of Ho3+:I75I85 can be derived from Eq. (1) by using the McCumber theory [46]:

σem(λ)=σabs(λ)×ZlZu×exp[hckT×(1λZL1λ)],
where Zl/Zu is the partition functions ratio involved in the considered optical transition. Here T is the room temperature, k is the Boltzmann constant, and λZL is the wavelength for the transition between the lower Stark sublevels of the emitting multiplets and the lower Stark sublevels of the receiving multiplets. The σabs is the absorption cross section of Tm3+/Ho3+ co-doped sample, which is calculated from the absorption spectra by using Eq. (2):
σabs(λ)=2.303log(I0/I)Nl,
where N is the concentration of Ho3+ ions, l is the thickness of the glass samples, and log(I0/I) is the absorptivity from absorption spectra, respectively.

Moreover, the emission cross section (σem) also can be calculated from the fluorescence spectrum by the Fuchtbauer–Ladenburg equation in Eq. (3):

σem(λ)=λ4Arad8πcn2×λI(λ)λI(λ)dλ,
where λ is the emission wavelength, Arad is the spontaneous radiative transition probability of Ho3+:I75I85 transition, c is the velocity of light in vacuum, n is the refractive index of glass host, I(λ) is the fluorescence intensity, and I(λ)dλ is the integrated fluorescence intensity.

Figure 5 shows the absorption and emission cross sections for Ho3+:I85I75 transition based on McCumber theory. According to the figure, it can be found that the peak absorption cross section of Ho3+:I85I75 transition in silicate-germanate glass reaches 2.77×1021  cm2 near 1946 nm, and the emission cross section of Ho3+ is 4.78×1021  cm2 at 2014 nm, respectively. The value of emission cross section is a little larger than that of fluoride glass [47] and silicate glass [44] but smaller than the value of germanate glass [48]. Compared with silicate (n=1.48) or phosphate (n=1.52) glasses [22], the prepared silicate-germanate glass has a high refractive index (n=1.7), the higher refractive index of the host glass induces the higher emission cross section of Ho3+, due to the electric dipole transitions of rare-earth ions increasing as the refractive index of the glass increases [22]. It is worth noting that the emission cross section is as large as possible to obtain high gain for a laser medium [49]. Thus, Tm3+/Ho3+ co-doped silicate-germanate glass could be a suitable candidate matrix for 2 μm optical fiber amplifier.

 

Fig. 5. Emission cross sections of silicate-germanate glasses doped with 1.5 mol% Tm2O3 and 1 mol% Ho2O3.

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G. Laser Spectroscopic Properties

Table 5 shows the emission cross-section σepeak and the FWHM of the emission peak of Ho3+:I75I85 transition in different glass hosts. The σepeak×FWHM is an important parameter in which to characterize the bandwidth properties of the optical amplifier materials, the larger value of which represents the wider gain bandwidth and the higher gain character [50]. The value of σepeak×τm is another parameter that can be applied to evaluate the gain of bandwidth [51]. As the results show in Table 5, σepeak×FWHM is 731.34×1028  cm3 and σepeak×τm is 46.22×1021  cm2·ms in this work, respectively. Those values are much larger than those of various glasses, excluding fluoride [8] glass, as shown in Table 5. Therefore, it is desirable that the Tm3+/Ho3+ co-doped silicate-germanate glass should become a suitable host material to be used as a candidate for broadband optical amplifiers or a 2 μm laser.

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Table 5. Peak Cross Section σepeak, FWHM, Radiative Lifetime τm, σepeak×FWHM and σepeak×τm of I75I85 Transition of Ho3+ in Different Glass Samples

H. Energy Transfer Efficiency

Figure 6 shows the decay curves of glass samples. By using the lifetime value of the Tm3+:F43 energy level, the energy transfer efficiency from Tm3+:F43 to Ho3+:I75 in silicate-germanate glass can be estimated as follows [52]:

η=1τTm/HoτTm.

 

Fig. 6. (a) Fluorescence decay curve of Tm3+/Ho3+ co-doped glass sample from Tm3+:F43H63. Inset shows the decay curve of Tm3+ singly doped glass sample. (b) Fluorescence decay curve of Tm3+/Ho3+ co-doped glass samples from Ho3+:I75I85.

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The energy transfer rate was found to be connected to the effective lifetime, which can be defined as [53]

WET=1τTm/Ho1τTm,
where τTm/Ho and τTm are the lifetimes of Tm3+ ions in Tm3+/Ho3+ co-doped and Tm3+ single-doped glass samples, respectively.

The quantum efficiency (Q.E.) was determined for the Ho3+:I75I85 in the Tm3+/Ho3+ co-doped silicate-germanate glass samples, as [54]

Q.E.=τobsτrad,
where τobs and τrad are the measured luminescence lifetime and radiative lifetime of Ho3+ ions, respectively.

According to Fig. 6, it can be found that the fluorescence lifetime of Tm3+:F43 becomes shorter as Ho3+ ions co-dope into the Tm3+-ions-doped sample. This indicates that energy transfer occurred between the Tm3+:F43 and Ho3+:I75 level. And the lifetimes of Tm3+:F43 with and without Ho3+ are 222 and 399 μs, and the measured lifetime of Ho3+:I75 in Tm3+/Ho3+ co-doped silicate-germanate glass is 210 μs, respectively. Thus, the energy-transfer efficiency and energy-transfer rate between Tm3+ and Ho3+ ions in silicate-germanate glass were calculated, which is 52% and 2760.55  s1, respectively. The efficiency value for energy transfer to Ho3+ from Tm3+ ions of the present glass is larger than that of fluorozircoaluminate glass [47]. The high value of energy transfer efficiency implied the high sensitization efficiency of Tm3+/Ho3+ in co-doped silicate-germanate glass here, which is helpful for development of the 2 μm laser. The Q.E. of the Ho3+:I75I85 transition is 2.17%, which is higher than that of silicate glass [43]. The results demonstrate that the incorporation of Tm3+ as a sensitizer through efficient energy transfer from Tm3+ (F43) to Ho3+ (I75) under 808 nm excitation can be obtained by 2 μm emission efficiently in the silicate-germanate glass.

4. CONCLUSION

In summary, Tm3+ doped and Tm3+/Ho3+ co-doped silicate-germanate glasses were prepared. We successfully obtain the 2 μm luminescence of Ho3+ in Tm3+/Ho3+ co-doped silicate-germanate glass under excitation of an 808 nm LD. The Tm3+/Ho3+ co-doped silicate-germanate glasses exhibited good thermal stability. According to the Raman spectrum, the structure features of the present silicate-germanate glass appears to contain alternating SiO4 tetrahedra, GeO4 tetrahedra, and NbO6 octahedra. The J-O intensity parameters, transition properties, branching ratios, and radiative lifetimes have been determined. The value of FWHM (153 nm) was recorded in Tm3+/Ho3+ co-doped SGTH2 glass at room temperature when pumped by 808 nm LD. Tm3+/Ho3+ co-doped silicate-germanate glasses exhibit large σepeak×FWHM (up to 731.34×1028  cm3), which indicates that the present glass has better gain properties as laser material. Furthermore, a large stimulated emission cross section and gain coefficient for Ho3+:I75I85 transition of Tm3+/Ho3+ co-doped silicate-germanate glasses indicate that these glasses find applications in mid-infrared laser devices at 2  μm. The energy transfer efficiency and rate were calculated to be 52% and 2760.55  s1, respectively. The Q.E. of the I75I85 transition of Ho3+ is 2.17%. As a result, Tm3+/Ho3+ co-doped silicate-germanate glass with good spectroscopic properties might be a promising candidate as a host for developing laser or optical amplifier devices.

Funding

Natural Science Foundation of Zhejiang Province of China (LY15E020009, LY13F050003, LR14E020003); National Natural Science Foundation of China (NSFC) (61370049, 61308090, 61405182, 51172252, 51372235, 51472225); International Science & Technology Cooperation Program of China (2013DFE63070); Public Technical International Cooperation Project of the Science Technology Department of Zhejiang Province (2015c340009).

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11. G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009). [CrossRef]  

12. L. Kong, G. Xie, P. Yuan, L. Qian, S. Wang, H. Yu, and H. Zhang, “Passive Q-switching and Q-switched mode-locking operations of 2  μm Tm:CLNGG laser with MoS2 saturable absorber mirror,” Photo. Res. 3, A47–A50 (2015). [CrossRef]  

13. W. Zhang, L. Rong, J. Ren, Y. Jia, and S. Qian, “Judd-Ofelt analysis and mid-infrared emission properties of Ho3+-Yb3+ co-doped tellurite oxy-halide glasses,” Proc. SPIE 8906, 89060 (2013).

14. G. Chen, Q. Zhang, G. Yang, and Z. Jiang, “Mid-infrared emission characteristic and energy transfer of Ho3+-doped tellurite glass sensitized by Tm3+,” J. Fluoresc. 17, 301–307 (2007). [CrossRef]  

15. S. D. Jackson, “The effects of energy transfer upconversion on the performance of Tm3+/Ho3+-doped silica fiber lasers,” IEEE Photon. Technol. Lett. 18, 1885–1887 (2006). [CrossRef]  

16. Q. Zhang, J. Ding, Y. Shen, G. Zhang, G. Lin, J. Qiu, and D. Chen, “Infrared emission properties and energy transfer between Tm3+ and Ho3+ in lanthanum aluminum germanate glasses,” J. Opt. Soc. Am. B 27, 975–980 (2010). [CrossRef]  

17. T. Wei, C. Tian, M. Z. Cai, Y. Tian, X. F. Jing, J. J. Zhang, and S. Q. Xu, “Broadband 2  μm fluorescence and energy transfer evaluation in Ho3+/Er3+ codoped germanosilicate glass,” J. Quant. Spectrosc. Radiat. Transfer 161, 95–104 (2015). [CrossRef]  

18. W. Fan, L. Htein, B. H. Kim, P. R. Watekar, and W. T. Han, “Upconversion luminescence in bismuth-doped germane-silicate glass optical fiber,” Opt. Laser Technol. 54, 376–379 (2013). [CrossRef]  

19. M. Li, G. Bai, Y. Guo, L. Hu, and J. Zhang, “Investigation on Tm3+-doped silicate glass for 1.8  μm emission,” J. Lumin. 132, 1830–1835 (2012). [CrossRef]  

20. S. S. Bayya, G. D. Chin, J. S. Sanghera, and I. D. Aggarwal, “Germanate glass as a window for high energy laser systems,” Opt. Express 14, 11687–11693 (2006). [CrossRef]  

21. Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Thermal analysis and optical transition of Yb3+, Er3+ co-doped lead-germanium-tellurite glasses,” J. Mater. Res. 19, 1630–1637 (2004). [CrossRef]  

22. D. Dorosz, “Rare earth ions doped aluminosilicate and phosphate double clad optical fibres,” Bull. Polish Acad. Sci. 56, 103–111 (2008).

23. G. Bai, L. Tao, K. Li, L. Hu, and Y. H. Tsang, “Enhanced light emission near 2.7  μm from Er-Nd co-doped germanate glass,” Opt. Mater. 35, 1247–1250 (2013). [CrossRef]  

24. T. Xue, L. Zhang, L. Wen, M. Liao, and L. Hu, “Er3+ doped fluorogallate glass for mid-infrared applications,” Chin. Opt. Lett. 13, 081602 (2015). [CrossRef]  

25. R. Xu, Y. Tian, L. Hu, and J. Zhang, “Broadband 2  μm emission and energy-transfer properties of thulium-doped oxyfluoride germanate glass fiber,” Appl. Phys. B 104, 839–844 (2011). [CrossRef]  

26. A. Hruby, “Evaluation of glass-forming tendency by means of DTA,” J. Phys. B 22, 1187–1193 (1972).

27. M. G. Drexhage, O. H. EI Bayoumi, and C. T. Moyniyan, “Preparation and properties of heavy-metal fluoride glasses containing ytterbium or lutetium,” J. Am. Ceram. Soc. 65, c168–c171 (1982). [CrossRef]  

28. Y. Messaddeq and M. Poulain, “Stabilizing effect of aluminium, yttrium and zirconium in divalent fluoride glasses,” J. Non-Cryst. Solids 140, 41–46 (1992). [CrossRef]  

29. F. Huang, X. Liu, W. Li, L. Hu, and D. Chen, “Energy transfer mechanism in Er3+ doped fluoride glass sensitized by Tm3+ or Ho3+ for 2.7  μm emission,” Chin. Opt. Lett. 12, 051601 (2014). [CrossRef]  

30. K. Fukumi and S. Sakka, “Coordination state of Nb5+ ions in silicate and gallate glasses as studied by Raman spectroscopy,” J. Mater. Sci. 23, 2819–2823 (1988). [CrossRef]  

31. A. Aronne, V. N. Sigaev, B. Champagnon, E. Fanelli, V. Califano, L. Z. Usmanova, and P. Pernice, “The origin of nanostructuring in potassium niobiosilicate glasses by Raman and FTIR spectroscopy,” J. Non-Cryst. Solids 351, 3610–3618 (2005). [CrossRef]  

32. H. Verweij, “Raman study of the structure of alkali germanosilicate glasses, Lithium, sodium and potassium digermanosilicate glasses,” J. Non-Cryst. Solids 33, 55–69 (1979). [CrossRef]  

33. Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Density of Na2O-(3-x)SiO2-xGeO2 glasses related to structure,” Mater. Res. Bull. 39, 217–222 (2004). [CrossRef]  

34. R. Xu, Y. Tian, L. Hu, and J. Zhang, “Structural origin and energy transfer processes of 1.8  μm emission in Tm3+ doped germanate glasses,” J. Phys. Chem. A. 115, 6488–6492 (2011). [CrossRef]  

35. G. S. Henderson, D. R. Neuville, B. Cochain, and L. Cormier, “The structure of GeO2-SiO2 glasses and melts: A Raman spectroscopy study,” J. Non-Cryst. Solids 355, 468–474 (2009). [CrossRef]  

36. E. V. Kolobkova, “Raman-spectroscopy study of the structure of niobium germanate glasses,” Soviet J. Glass Phys. Chem. 13, 176–181 (1988).

37. K. Awazu and H. Kawazoe, “Strained Si-O–Si bonds in amorphous SiO2 materials: A family member of active centers in radio, photo, and chemical responses,” J. Appl. Phys. 94, 6243–6262 (2003). [CrossRef]  

38. B. Judd, “Optical absorption intensities of rare-earth ions,” Phys. Rev. 127, 750–761 (1962). [CrossRef]  

39. G. Ofelt, “Intensities of crystal spectra of rare-earth ions,” J. Chem. Phys. 37, 511–520 (1962). [CrossRef]  

40. E. Rukmini and C. K. Jayasankar, “Spectroscopic properties of Ho3+ ion in zinc borosulphate glasses and comparative energy level analyses of Ho3+ ion in various glasses,” Opt. Mater. 4, 529–546 (1995). [CrossRef]  

41. B. Peng and T. Lzumitani, “Optical properties, fluorescence mechanisms and energy transfer in Tm3+, Ho3+ and Tm3+-Ho3+ doped near-infrared laser glasses, sensitized by Yb3+,” Opt. Mater. 4, 797–810 (1995). [CrossRef]  

42. K. Binnemans, R. Deun, C. Walrand, and J. Adam, “Spectroscopic properties of trivalent lanthanide ions in fluorophosphates glasses,” J. Non-Cryst. Solids 238, 11–29 (1998). [CrossRef]  

43. X. Li, X. Liu, L. Zhang, L. Hu, and J. Zhang, “Emission enhancement in Er3+/Pr3+-codoped germanate glasses and their use as a 2.7  μm laser material,” Chin. Opt. Lett. 11, 121601 (2013). [CrossRef]  

44. M. Li, X. Liu, Y. Guo, L. Hu, and J. Zhang, “Energy transfer characteristics of silicate glass doped with Er3+, Tm3+, and Ho3+ for 2  μm emission,” J. Appl. Phys. 114, 243501 (2013). [CrossRef]  

45. M. Wang, L. Yi, G. Wang, L. Hu, and J. Zhang, “Emission performance in Ho3+ doped fluorophosphates glasses sensitized with Er3+ and Tm3+ under 800  nm excitation,” Solid State Commun. 149, 1216–1220 (2009). [CrossRef]  

46. D. E. McCumber, “Einstein relations connecting broadband emission and absorption spectra,” Phys. Rev. 136, A954–A957 (1964). [CrossRef]  

47. X. Zou and H. Toratani, “Spectroscopic properties and energy transfer in Tm3+ singly-and Tm3+/Ho3+ doubly-doped glasses,” J. Non-Cryst. Solids 195, 113–124 (1996). [CrossRef]  

48. R. Xu, M. Wang, Y. Tian, L. Hu, and J. Zhang, “2.05  μm emission properties and energy transfer mechanism of germanate glass doped with Ho3+, Tm3+, and Er3+,” J. Appl. Phys. 109, 053503 (2011). [CrossRef]  

49. J. Ding, G. Zhao, Y. Tian, W. Chen, and L. Hu, “Bismuth silicate glass: a new choice for 2  μm fiber lasers,” Opt. Mater. 35, 85–88 (2012). [CrossRef]  

50. Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Thermal analysis and optical properties of Yb3+/Er3+codoped oxyfluoride germanate glasses,” J. Opt. Soc. Am. B 21, 951–957 (2004). [CrossRef]  

51. D. Shi, Q. Zhang, G. Yang, and Z. Jiang, “Spectroscopic properties and energy transfer in Ga2O3-Bi2O3-PbO-GeO2 glasses codoped with Tm3+ and Ho3+,” J. Non-Cryst. Solids 353, 1508–1514 (2007). [CrossRef]  

52. K. Li, Q. Zhang, S. Fan, L. Zhang, J. Zhang, and L. Hu, “Mid-infrared luminescence and energy transfer characteristics of Ho3+/Yb3+codoped lanthanum-tungsten-tellurite glasses,” Opt. Mater. 33, 31–35 (2010). [CrossRef]  

53. A. Braud, S. Girard, J. L. Doualan, M. Thuau, and R. Moncorgé, “Energy-transfer processes in Yb:Tm-doped KY3F10, LiYF4, and BaY2F8 single crystals for laser operation at 1.5 and 2.3  μm,” Phys. Rev. B. 61, 5280–5292 (2000). [CrossRef]  

54. L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007). [CrossRef]  

References

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  1. B. Richards, A. Jha, Y. Tsang, and W. Sibbett, “Tellurite glass lasers operating close to 2  μm,” Laser Phys. Lett. 7, 177–193 (2010).
    [Crossref]
  2. G. J. Koch, M. Petros, J. Yu, and U. N. Singh, “Precise wavelength control of a single-frequency pulsed Ho:Tm:YLF laser,” Appl. Opt. 41, 1718–1721 (2002).
    [Crossref]
  3. K. Scholle, E. Heumann, and G. Huber, “Single mode tm and Tm, Ho: LuAG lasers for LIDAR applications,” Laser Phys. Lett. 1, 285–290 (2004).
    [Crossref]
  4. R. Cao, M. Peng, L. Wondraczek, and J. Qiu, “Superbroad near-to-mid-infrared luminescence from Bi53+ in Bi5(AlCl4)3,” Opt. Express 20, 2562–2571 (2012).
    [Crossref]
  5. S. Li, P. Wang, H. Xia, J. Peng, L. Tang, Y. Zhang, and H. Jiang, “Tm3+ and Nd3+ singly doped LiYF4 single crystals with 3–5  μm mid-infrared luminescence,” Chin. Opt. Lett. 12, 021601 (2014).
    [Crossref]
  6. A. Hemming, S. Bennetts, N. Simakov, A. Davidson, J. Haub, and A. Carter, “High power operation of cladding pumped holmium-doped silica fiber lasers,” Opt. Express 21, 4560–4566 (2013).
    [Crossref]
  7. C. Liu, C. Ye, Z. Luo, H. Cheng, D. Wu, Y. Zheng, Z. Liu, and B. Qu, “High-energy passively Q-switched 2  μm Tm3+-doped double-clad fiber laser using graphene-oxide–deposited fiber taper,” Opt. Express 21, 204–209 (2013).
    [Crossref]
  8. L. Yi, M. Wang, S. Feng, Y. Chen, G. Wang, L. Hu, and J. Zhang, “Emission properties of Ho3+: 5I7 → 5I8 transition sensitized by Er3+ and Yb3+ in fluorophosphates glasses,” Opt. Mater. 31, 1586–1590 (2009).
    [Crossref]
  9. B. S. Yong, H. T. Lim, Y. G. Choi, Y. S. Kim, and J. Heo, “2.0  μm emission properties and energy transfer between Ho3+ and Tm3+ in PbO-Bi2O3-Ga2O3 glasses,” J. Am. Ceram. Soc. 83, 787–791 (2000).
  10. Y. Ju, W. Liu, B. Yao, T. Dai, J. Wu, J. Yuan, J. Wang, X. Duan, and Y. Wang, “Diode-pumped tunable single-longitudinal-mode Tm, Ho:YAG twisted-mode laser,” Chin. Opt. Lett. 13, 111403 (2015).
    [Crossref]
  11. G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009).
    [Crossref]
  12. L. Kong, G. Xie, P. Yuan, L. Qian, S. Wang, H. Yu, and H. Zhang, “Passive Q-switching and Q-switched mode-locking operations of 2  μm Tm:CLNGG laser with MoS2 saturable absorber mirror,” Photo. Res. 3, A47–A50 (2015).
    [Crossref]
  13. W. Zhang, L. Rong, J. Ren, Y. Jia, and S. Qian, “Judd-Ofelt analysis and mid-infrared emission properties of Ho3+-Yb3+ co-doped tellurite oxy-halide glasses,” Proc. SPIE 8906, 89060 (2013).
  14. G. Chen, Q. Zhang, G. Yang, and Z. Jiang, “Mid-infrared emission characteristic and energy transfer of Ho3+-doped tellurite glass sensitized by Tm3+,” J. Fluoresc. 17, 301–307 (2007).
    [Crossref]
  15. S. D. Jackson, “The effects of energy transfer upconversion on the performance of Tm3+/Ho3+-doped silica fiber lasers,” IEEE Photon. Technol. Lett. 18, 1885–1887 (2006).
    [Crossref]
  16. Q. Zhang, J. Ding, Y. Shen, G. Zhang, G. Lin, J. Qiu, and D. Chen, “Infrared emission properties and energy transfer between Tm3+ and Ho3+ in lanthanum aluminum germanate glasses,” J. Opt. Soc. Am. B 27, 975–980 (2010).
    [Crossref]
  17. T. Wei, C. Tian, M. Z. Cai, Y. Tian, X. F. Jing, J. J. Zhang, and S. Q. Xu, “Broadband 2  μm fluorescence and energy transfer evaluation in Ho3+/Er3+ codoped germanosilicate glass,” J. Quant. Spectrosc. Radiat. Transfer 161, 95–104 (2015).
    [Crossref]
  18. W. Fan, L. Htein, B. H. Kim, P. R. Watekar, and W. T. Han, “Upconversion luminescence in bismuth-doped germane-silicate glass optical fiber,” Opt. Laser Technol. 54, 376–379 (2013).
    [Crossref]
  19. M. Li, G. Bai, Y. Guo, L. Hu, and J. Zhang, “Investigation on Tm3+-doped silicate glass for 1.8  μm emission,” J. Lumin. 132, 1830–1835 (2012).
    [Crossref]
  20. S. S. Bayya, G. D. Chin, J. S. Sanghera, and I. D. Aggarwal, “Germanate glass as a window for high energy laser systems,” Opt. Express 14, 11687–11693 (2006).
    [Crossref]
  21. Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Thermal analysis and optical transition of Yb3+, Er3+ co-doped lead-germanium-tellurite glasses,” J. Mater. Res. 19, 1630–1637 (2004).
    [Crossref]
  22. D. Dorosz, “Rare earth ions doped aluminosilicate and phosphate double clad optical fibres,” Bull. Polish Acad. Sci. 56, 103–111 (2008).
  23. G. Bai, L. Tao, K. Li, L. Hu, and Y. H. Tsang, “Enhanced light emission near 2.7  μm from Er-Nd co-doped germanate glass,” Opt. Mater. 35, 1247–1250 (2013).
    [Crossref]
  24. T. Xue, L. Zhang, L. Wen, M. Liao, and L. Hu, “Er3+ doped fluorogallate glass for mid-infrared applications,” Chin. Opt. Lett. 13, 081602 (2015).
    [Crossref]
  25. R. Xu, Y. Tian, L. Hu, and J. Zhang, “Broadband 2  μm emission and energy-transfer properties of thulium-doped oxyfluoride germanate glass fiber,” Appl. Phys. B 104, 839–844 (2011).
    [Crossref]
  26. A. Hruby, “Evaluation of glass-forming tendency by means of DTA,” J. Phys. B 22, 1187–1193 (1972).
  27. M. G. Drexhage, O. H. EI Bayoumi, and C. T. Moyniyan, “Preparation and properties of heavy-metal fluoride glasses containing ytterbium or lutetium,” J. Am. Ceram. Soc. 65, c168–c171 (1982).
    [Crossref]
  28. Y. Messaddeq and M. Poulain, “Stabilizing effect of aluminium, yttrium and zirconium in divalent fluoride glasses,” J. Non-Cryst. Solids 140, 41–46 (1992).
    [Crossref]
  29. F. Huang, X. Liu, W. Li, L. Hu, and D. Chen, “Energy transfer mechanism in Er3+ doped fluoride glass sensitized by Tm3+ or Ho3+ for 2.7  μm emission,” Chin. Opt. Lett. 12, 051601 (2014).
    [Crossref]
  30. K. Fukumi and S. Sakka, “Coordination state of Nb5+ ions in silicate and gallate glasses as studied by Raman spectroscopy,” J. Mater. Sci. 23, 2819–2823 (1988).
    [Crossref]
  31. A. Aronne, V. N. Sigaev, B. Champagnon, E. Fanelli, V. Califano, L. Z. Usmanova, and P. Pernice, “The origin of nanostructuring in potassium niobiosilicate glasses by Raman and FTIR spectroscopy,” J. Non-Cryst. Solids 351, 3610–3618 (2005).
    [Crossref]
  32. H. Verweij, “Raman study of the structure of alkali germanosilicate glasses, Lithium, sodium and potassium digermanosilicate glasses,” J. Non-Cryst. Solids 33, 55–69 (1979).
    [Crossref]
  33. Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Density of Na2O-(3-x)SiO2-xGeO2 glasses related to structure,” Mater. Res. Bull. 39, 217–222 (2004).
    [Crossref]
  34. R. Xu, Y. Tian, L. Hu, and J. Zhang, “Structural origin and energy transfer processes of 1.8  μm emission in Tm3+ doped germanate glasses,” J. Phys. Chem. A. 115, 6488–6492 (2011).
    [Crossref]
  35. G. S. Henderson, D. R. Neuville, B. Cochain, and L. Cormier, “The structure of GeO2-SiO2 glasses and melts: A Raman spectroscopy study,” J. Non-Cryst. Solids 355, 468–474 (2009).
    [Crossref]
  36. E. V. Kolobkova, “Raman-spectroscopy study of the structure of niobium germanate glasses,” Soviet J. Glass Phys. Chem. 13, 176–181 (1988).
  37. K. Awazu and H. Kawazoe, “Strained Si-O–Si bonds in amorphous SiO2 materials: A family member of active centers in radio, photo, and chemical responses,” J. Appl. Phys. 94, 6243–6262 (2003).
    [Crossref]
  38. B. Judd, “Optical absorption intensities of rare-earth ions,” Phys. Rev. 127, 750–761 (1962).
    [Crossref]
  39. G. Ofelt, “Intensities of crystal spectra of rare-earth ions,” J. Chem. Phys. 37, 511–520 (1962).
    [Crossref]
  40. E. Rukmini and C. K. Jayasankar, “Spectroscopic properties of Ho3+ ion in zinc borosulphate glasses and comparative energy level analyses of Ho3+ ion in various glasses,” Opt. Mater. 4, 529–546 (1995).
    [Crossref]
  41. B. Peng and T. Lzumitani, “Optical properties, fluorescence mechanisms and energy transfer in Tm3+, Ho3+ and Tm3+-Ho3+ doped near-infrared laser glasses, sensitized by Yb3+,” Opt. Mater. 4, 797–810 (1995).
    [Crossref]
  42. K. Binnemans, R. Deun, C. Walrand, and J. Adam, “Spectroscopic properties of trivalent lanthanide ions in fluorophosphates glasses,” J. Non-Cryst. Solids 238, 11–29 (1998).
    [Crossref]
  43. X. Li, X. Liu, L. Zhang, L. Hu, and J. Zhang, “Emission enhancement in Er3+/Pr3+-codoped germanate glasses and their use as a 2.7  μm laser material,” Chin. Opt. Lett. 11, 121601 (2013).
    [Crossref]
  44. M. Li, X. Liu, Y. Guo, L. Hu, and J. Zhang, “Energy transfer characteristics of silicate glass doped with Er3+, Tm3+, and Ho3+ for 2  μm emission,” J. Appl. Phys. 114, 243501 (2013).
    [Crossref]
  45. M. Wang, L. Yi, G. Wang, L. Hu, and J. Zhang, “Emission performance in Ho3+ doped fluorophosphates glasses sensitized with Er3+ and Tm3+ under 800  nm excitation,” Solid State Commun. 149, 1216–1220 (2009).
    [Crossref]
  46. D. E. McCumber, “Einstein relations connecting broadband emission and absorption spectra,” Phys. Rev. 136, A954–A957 (1964).
    [Crossref]
  47. X. Zou and H. Toratani, “Spectroscopic properties and energy transfer in Tm3+ singly-and Tm3+/Ho3+ doubly-doped glasses,” J. Non-Cryst. Solids 195, 113–124 (1996).
    [Crossref]
  48. R. Xu, M. Wang, Y. Tian, L. Hu, and J. Zhang, “2.05  μm emission properties and energy transfer mechanism of germanate glass doped with Ho3+, Tm3+, and Er3+,” J. Appl. Phys. 109, 053503 (2011).
    [Crossref]
  49. J. Ding, G. Zhao, Y. Tian, W. Chen, and L. Hu, “Bismuth silicate glass: a new choice for 2  μm fiber lasers,” Opt. Mater. 35, 85–88 (2012).
    [Crossref]
  50. Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Thermal analysis and optical properties of Yb3+/Er3+codoped oxyfluoride germanate glasses,” J. Opt. Soc. Am. B 21, 951–957 (2004).
    [Crossref]
  51. D. Shi, Q. Zhang, G. Yang, and Z. Jiang, “Spectroscopic properties and energy transfer in Ga2O3-Bi2O3-PbO-GeO2 glasses codoped with Tm3+ and Ho3+,” J. Non-Cryst. Solids 353, 1508–1514 (2007).
    [Crossref]
  52. K. Li, Q. Zhang, S. Fan, L. Zhang, J. Zhang, and L. Hu, “Mid-infrared luminescence and energy transfer characteristics of Ho3+/Yb3+codoped lanthanum-tungsten-tellurite glasses,” Opt. Mater. 33, 31–35 (2010).
    [Crossref]
  53. A. Braud, S. Girard, J. L. Doualan, M. Thuau, and R. Moncorgé, “Energy-transfer processes in Yb:Tm-doped KY3F10, LiYF4, and BaY2F8 single crystals for laser operation at 1.5 and 2.3  μm,” Phys. Rev. B. 61, 5280–5292 (2000).
    [Crossref]
  54. L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007).
    [Crossref]

2015 (4)

L. Kong, G. Xie, P. Yuan, L. Qian, S. Wang, H. Yu, and H. Zhang, “Passive Q-switching and Q-switched mode-locking operations of 2  μm Tm:CLNGG laser with MoS2 saturable absorber mirror,” Photo. Res. 3, A47–A50 (2015).
[Crossref]

T. Wei, C. Tian, M. Z. Cai, Y. Tian, X. F. Jing, J. J. Zhang, and S. Q. Xu, “Broadband 2  μm fluorescence and energy transfer evaluation in Ho3+/Er3+ codoped germanosilicate glass,” J. Quant. Spectrosc. Radiat. Transfer 161, 95–104 (2015).
[Crossref]

Y. Ju, W. Liu, B. Yao, T. Dai, J. Wu, J. Yuan, J. Wang, X. Duan, and Y. Wang, “Diode-pumped tunable single-longitudinal-mode Tm, Ho:YAG twisted-mode laser,” Chin. Opt. Lett. 13, 111403 (2015).
[Crossref]

T. Xue, L. Zhang, L. Wen, M. Liao, and L. Hu, “Er3+ doped fluorogallate glass for mid-infrared applications,” Chin. Opt. Lett. 13, 081602 (2015).
[Crossref]

2014 (2)

2013 (7)

A. Hemming, S. Bennetts, N. Simakov, A. Davidson, J. Haub, and A. Carter, “High power operation of cladding pumped holmium-doped silica fiber lasers,” Opt. Express 21, 4560–4566 (2013).
[Crossref]

C. Liu, C. Ye, Z. Luo, H. Cheng, D. Wu, Y. Zheng, Z. Liu, and B. Qu, “High-energy passively Q-switched 2  μm Tm3+-doped double-clad fiber laser using graphene-oxide–deposited fiber taper,” Opt. Express 21, 204–209 (2013).
[Crossref]

W. Fan, L. Htein, B. H. Kim, P. R. Watekar, and W. T. Han, “Upconversion luminescence in bismuth-doped germane-silicate glass optical fiber,” Opt. Laser Technol. 54, 376–379 (2013).
[Crossref]

W. Zhang, L. Rong, J. Ren, Y. Jia, and S. Qian, “Judd-Ofelt analysis and mid-infrared emission properties of Ho3+-Yb3+ co-doped tellurite oxy-halide glasses,” Proc. SPIE 8906, 89060 (2013).

G. Bai, L. Tao, K. Li, L. Hu, and Y. H. Tsang, “Enhanced light emission near 2.7  μm from Er-Nd co-doped germanate glass,” Opt. Mater. 35, 1247–1250 (2013).
[Crossref]

X. Li, X. Liu, L. Zhang, L. Hu, and J. Zhang, “Emission enhancement in Er3+/Pr3+-codoped germanate glasses and their use as a 2.7  μm laser material,” Chin. Opt. Lett. 11, 121601 (2013).
[Crossref]

M. Li, X. Liu, Y. Guo, L. Hu, and J. Zhang, “Energy transfer characteristics of silicate glass doped with Er3+, Tm3+, and Ho3+ for 2  μm emission,” J. Appl. Phys. 114, 243501 (2013).
[Crossref]

2012 (3)

J. Ding, G. Zhao, Y. Tian, W. Chen, and L. Hu, “Bismuth silicate glass: a new choice for 2  μm fiber lasers,” Opt. Mater. 35, 85–88 (2012).
[Crossref]

M. Li, G. Bai, Y. Guo, L. Hu, and J. Zhang, “Investigation on Tm3+-doped silicate glass for 1.8  μm emission,” J. Lumin. 132, 1830–1835 (2012).
[Crossref]

R. Cao, M. Peng, L. Wondraczek, and J. Qiu, “Superbroad near-to-mid-infrared luminescence from Bi53+ in Bi5(AlCl4)3,” Opt. Express 20, 2562–2571 (2012).
[Crossref]

2011 (3)

R. Xu, Y. Tian, L. Hu, and J. Zhang, “Broadband 2  μm emission and energy-transfer properties of thulium-doped oxyfluoride germanate glass fiber,” Appl. Phys. B 104, 839–844 (2011).
[Crossref]

R. Xu, Y. Tian, L. Hu, and J. Zhang, “Structural origin and energy transfer processes of 1.8  μm emission in Tm3+ doped germanate glasses,” J. Phys. Chem. A. 115, 6488–6492 (2011).
[Crossref]

R. Xu, M. Wang, Y. Tian, L. Hu, and J. Zhang, “2.05  μm emission properties and energy transfer mechanism of germanate glass doped with Ho3+, Tm3+, and Er3+,” J. Appl. Phys. 109, 053503 (2011).
[Crossref]

2010 (3)

K. Li, Q. Zhang, S. Fan, L. Zhang, J. Zhang, and L. Hu, “Mid-infrared luminescence and energy transfer characteristics of Ho3+/Yb3+codoped lanthanum-tungsten-tellurite glasses,” Opt. Mater. 33, 31–35 (2010).
[Crossref]

Q. Zhang, J. Ding, Y. Shen, G. Zhang, G. Lin, J. Qiu, and D. Chen, “Infrared emission properties and energy transfer between Tm3+ and Ho3+ in lanthanum aluminum germanate glasses,” J. Opt. Soc. Am. B 27, 975–980 (2010).
[Crossref]

B. Richards, A. Jha, Y. Tsang, and W. Sibbett, “Tellurite glass lasers operating close to 2  μm,” Laser Phys. Lett. 7, 177–193 (2010).
[Crossref]

2009 (4)

L. Yi, M. Wang, S. Feng, Y. Chen, G. Wang, L. Hu, and J. Zhang, “Emission properties of Ho3+: 5I7 → 5I8 transition sensitized by Er3+ and Yb3+ in fluorophosphates glasses,” Opt. Mater. 31, 1586–1590 (2009).
[Crossref]

G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009).
[Crossref]

G. S. Henderson, D. R. Neuville, B. Cochain, and L. Cormier, “The structure of GeO2-SiO2 glasses and melts: A Raman spectroscopy study,” J. Non-Cryst. Solids 355, 468–474 (2009).
[Crossref]

M. Wang, L. Yi, G. Wang, L. Hu, and J. Zhang, “Emission performance in Ho3+ doped fluorophosphates glasses sensitized with Er3+ and Tm3+ under 800  nm excitation,” Solid State Commun. 149, 1216–1220 (2009).
[Crossref]

2008 (1)

D. Dorosz, “Rare earth ions doped aluminosilicate and phosphate double clad optical fibres,” Bull. Polish Acad. Sci. 56, 103–111 (2008).

2007 (3)

G. Chen, Q. Zhang, G. Yang, and Z. Jiang, “Mid-infrared emission characteristic and energy transfer of Ho3+-doped tellurite glass sensitized by Tm3+,” J. Fluoresc. 17, 301–307 (2007).
[Crossref]

D. Shi, Q. Zhang, G. Yang, and Z. Jiang, “Spectroscopic properties and energy transfer in Ga2O3-Bi2O3-PbO-GeO2 glasses codoped with Tm3+ and Ho3+,” J. Non-Cryst. Solids 353, 1508–1514 (2007).
[Crossref]

L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007).
[Crossref]

2006 (2)

S. D. Jackson, “The effects of energy transfer upconversion on the performance of Tm3+/Ho3+-doped silica fiber lasers,” IEEE Photon. Technol. Lett. 18, 1885–1887 (2006).
[Crossref]

S. S. Bayya, G. D. Chin, J. S. Sanghera, and I. D. Aggarwal, “Germanate glass as a window for high energy laser systems,” Opt. Express 14, 11687–11693 (2006).
[Crossref]

2005 (1)

A. Aronne, V. N. Sigaev, B. Champagnon, E. Fanelli, V. Califano, L. Z. Usmanova, and P. Pernice, “The origin of nanostructuring in potassium niobiosilicate glasses by Raman and FTIR spectroscopy,” J. Non-Cryst. Solids 351, 3610–3618 (2005).
[Crossref]

2004 (4)

Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Density of Na2O-(3-x)SiO2-xGeO2 glasses related to structure,” Mater. Res. Bull. 39, 217–222 (2004).
[Crossref]

Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Thermal analysis and optical transition of Yb3+, Er3+ co-doped lead-germanium-tellurite glasses,” J. Mater. Res. 19, 1630–1637 (2004).
[Crossref]

K. Scholle, E. Heumann, and G. Huber, “Single mode tm and Tm, Ho: LuAG lasers for LIDAR applications,” Laser Phys. Lett. 1, 285–290 (2004).
[Crossref]

Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Thermal analysis and optical properties of Yb3+/Er3+codoped oxyfluoride germanate glasses,” J. Opt. Soc. Am. B 21, 951–957 (2004).
[Crossref]

2003 (1)

K. Awazu and H. Kawazoe, “Strained Si-O–Si bonds in amorphous SiO2 materials: A family member of active centers in radio, photo, and chemical responses,” J. Appl. Phys. 94, 6243–6262 (2003).
[Crossref]

2002 (1)

2000 (2)

B. S. Yong, H. T. Lim, Y. G. Choi, Y. S. Kim, and J. Heo, “2.0  μm emission properties and energy transfer between Ho3+ and Tm3+ in PbO-Bi2O3-Ga2O3 glasses,” J. Am. Ceram. Soc. 83, 787–791 (2000).

A. Braud, S. Girard, J. L. Doualan, M. Thuau, and R. Moncorgé, “Energy-transfer processes in Yb:Tm-doped KY3F10, LiYF4, and BaY2F8 single crystals for laser operation at 1.5 and 2.3  μm,” Phys. Rev. B. 61, 5280–5292 (2000).
[Crossref]

1998 (1)

K. Binnemans, R. Deun, C. Walrand, and J. Adam, “Spectroscopic properties of trivalent lanthanide ions in fluorophosphates glasses,” J. Non-Cryst. Solids 238, 11–29 (1998).
[Crossref]

1996 (1)

X. Zou and H. Toratani, “Spectroscopic properties and energy transfer in Tm3+ singly-and Tm3+/Ho3+ doubly-doped glasses,” J. Non-Cryst. Solids 195, 113–124 (1996).
[Crossref]

1995 (2)

E. Rukmini and C. K. Jayasankar, “Spectroscopic properties of Ho3+ ion in zinc borosulphate glasses and comparative energy level analyses of Ho3+ ion in various glasses,” Opt. Mater. 4, 529–546 (1995).
[Crossref]

B. Peng and T. Lzumitani, “Optical properties, fluorescence mechanisms and energy transfer in Tm3+, Ho3+ and Tm3+-Ho3+ doped near-infrared laser glasses, sensitized by Yb3+,” Opt. Mater. 4, 797–810 (1995).
[Crossref]

1992 (1)

Y. Messaddeq and M. Poulain, “Stabilizing effect of aluminium, yttrium and zirconium in divalent fluoride glasses,” J. Non-Cryst. Solids 140, 41–46 (1992).
[Crossref]

1988 (2)

E. V. Kolobkova, “Raman-spectroscopy study of the structure of niobium germanate glasses,” Soviet J. Glass Phys. Chem. 13, 176–181 (1988).

K. Fukumi and S. Sakka, “Coordination state of Nb5+ ions in silicate and gallate glasses as studied by Raman spectroscopy,” J. Mater. Sci. 23, 2819–2823 (1988).
[Crossref]

1982 (1)

M. G. Drexhage, O. H. EI Bayoumi, and C. T. Moyniyan, “Preparation and properties of heavy-metal fluoride glasses containing ytterbium or lutetium,” J. Am. Ceram. Soc. 65, c168–c171 (1982).
[Crossref]

1979 (1)

H. Verweij, “Raman study of the structure of alkali germanosilicate glasses, Lithium, sodium and potassium digermanosilicate glasses,” J. Non-Cryst. Solids 33, 55–69 (1979).
[Crossref]

1972 (1)

A. Hruby, “Evaluation of glass-forming tendency by means of DTA,” J. Phys. B 22, 1187–1193 (1972).

1964 (1)

D. E. McCumber, “Einstein relations connecting broadband emission and absorption spectra,” Phys. Rev. 136, A954–A957 (1964).
[Crossref]

1962 (2)

B. Judd, “Optical absorption intensities of rare-earth ions,” Phys. Rev. 127, 750–761 (1962).
[Crossref]

G. Ofelt, “Intensities of crystal spectra of rare-earth ions,” J. Chem. Phys. 37, 511–520 (1962).
[Crossref]

Adam, J.

K. Binnemans, R. Deun, C. Walrand, and J. Adam, “Spectroscopic properties of trivalent lanthanide ions in fluorophosphates glasses,” J. Non-Cryst. Solids 238, 11–29 (1998).
[Crossref]

Aggarwal, I. D.

Almeida, R. M.

L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007).
[Crossref]

Aronne, A.

A. Aronne, V. N. Sigaev, B. Champagnon, E. Fanelli, V. Califano, L. Z. Usmanova, and P. Pernice, “The origin of nanostructuring in potassium niobiosilicate glasses by Raman and FTIR spectroscopy,” J. Non-Cryst. Solids 351, 3610–3618 (2005).
[Crossref]

Awazu, K.

K. Awazu and H. Kawazoe, “Strained Si-O–Si bonds in amorphous SiO2 materials: A family member of active centers in radio, photo, and chemical responses,” J. Appl. Phys. 94, 6243–6262 (2003).
[Crossref]

Bai, G.

G. Bai, L. Tao, K. Li, L. Hu, and Y. H. Tsang, “Enhanced light emission near 2.7  μm from Er-Nd co-doped germanate glass,” Opt. Mater. 35, 1247–1250 (2013).
[Crossref]

M. Li, G. Bai, Y. Guo, L. Hu, and J. Zhang, “Investigation on Tm3+-doped silicate glass for 1.8  μm emission,” J. Lumin. 132, 1830–1835 (2012).
[Crossref]

Bayya, S. S.

Bennetts, S.

Binnemans, K.

K. Binnemans, R. Deun, C. Walrand, and J. Adam, “Spectroscopic properties of trivalent lanthanide ions in fluorophosphates glasses,” J. Non-Cryst. Solids 238, 11–29 (1998).
[Crossref]

Braud, A.

A. Braud, S. Girard, J. L. Doualan, M. Thuau, and R. Moncorgé, “Energy-transfer processes in Yb:Tm-doped KY3F10, LiYF4, and BaY2F8 single crystals for laser operation at 1.5 and 2.3  μm,” Phys. Rev. B. 61, 5280–5292 (2000).
[Crossref]

Cai, M. Z.

T. Wei, C. Tian, M. Z. Cai, Y. Tian, X. F. Jing, J. J. Zhang, and S. Q. Xu, “Broadband 2  μm fluorescence and energy transfer evaluation in Ho3+/Er3+ codoped germanosilicate glass,” J. Quant. Spectrosc. Radiat. Transfer 161, 95–104 (2015).
[Crossref]

Califano, V.

A. Aronne, V. N. Sigaev, B. Champagnon, E. Fanelli, V. Califano, L. Z. Usmanova, and P. Pernice, “The origin of nanostructuring in potassium niobiosilicate glasses by Raman and FTIR spectroscopy,” J. Non-Cryst. Solids 351, 3610–3618 (2005).
[Crossref]

Cao, R.

Carter, A.

Champagnon, B.

A. Aronne, V. N. Sigaev, B. Champagnon, E. Fanelli, V. Califano, L. Z. Usmanova, and P. Pernice, “The origin of nanostructuring in potassium niobiosilicate glasses by Raman and FTIR spectroscopy,” J. Non-Cryst. Solids 351, 3610–3618 (2005).
[Crossref]

Chaussedent, S.

L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007).
[Crossref]

Chen, D.

Chen, G.

G. Chen, Q. Zhang, G. Yang, and Z. Jiang, “Mid-infrared emission characteristic and energy transfer of Ho3+-doped tellurite glass sensitized by Tm3+,” J. Fluoresc. 17, 301–307 (2007).
[Crossref]

Chen, H.

G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009).
[Crossref]

Chen, W.

J. Ding, G. Zhao, Y. Tian, W. Chen, and L. Hu, “Bismuth silicate glass: a new choice for 2  μm fiber lasers,” Opt. Mater. 35, 85–88 (2012).
[Crossref]

Chen, Y.

L. Yi, M. Wang, S. Feng, Y. Chen, G. Wang, L. Hu, and J. Zhang, “Emission properties of Ho3+: 5I7 → 5I8 transition sensitized by Er3+ and Yb3+ in fluorophosphates glasses,” Opt. Mater. 31, 1586–1590 (2009).
[Crossref]

Cheng, H.

Chiasera, A.

L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007).
[Crossref]

Chin, G. D.

Choi, Y. G.

B. S. Yong, H. T. Lim, Y. G. Choi, Y. S. Kim, and J. Heo, “2.0  μm emission properties and energy transfer between Ho3+ and Tm3+ in PbO-Bi2O3-Ga2O3 glasses,” J. Am. Ceram. Soc. 83, 787–791 (2000).

Cochain, B.

G. S. Henderson, D. R. Neuville, B. Cochain, and L. Cormier, “The structure of GeO2-SiO2 glasses and melts: A Raman spectroscopy study,” J. Non-Cryst. Solids 355, 468–474 (2009).
[Crossref]

Cormier, L.

G. S. Henderson, D. R. Neuville, B. Cochain, and L. Cormier, “The structure of GeO2-SiO2 glasses and melts: A Raman spectroscopy study,” J. Non-Cryst. Solids 355, 468–474 (2009).
[Crossref]

Dai, T.

Davidson, A.

Deun, R.

K. Binnemans, R. Deun, C. Walrand, and J. Adam, “Spectroscopic properties of trivalent lanthanide ions in fluorophosphates glasses,” J. Non-Cryst. Solids 238, 11–29 (1998).
[Crossref]

Ding, J.

Dorosz, D.

D. Dorosz, “Rare earth ions doped aluminosilicate and phosphate double clad optical fibres,” Bull. Polish Acad. Sci. 56, 103–111 (2008).

Doualan, J. L.

A. Braud, S. Girard, J. L. Doualan, M. Thuau, and R. Moncorgé, “Energy-transfer processes in Yb:Tm-doped KY3F10, LiYF4, and BaY2F8 single crystals for laser operation at 1.5 and 2.3  μm,” Phys. Rev. B. 61, 5280–5292 (2000).
[Crossref]

Drexhage, M. G.

M. G. Drexhage, O. H. EI Bayoumi, and C. T. Moyniyan, “Preparation and properties of heavy-metal fluoride glasses containing ytterbium or lutetium,” J. Am. Ceram. Soc. 65, c168–c171 (1982).
[Crossref]

Duan, X.

EI Bayoumi, O. H.

M. G. Drexhage, O. H. EI Bayoumi, and C. T. Moyniyan, “Preparation and properties of heavy-metal fluoride glasses containing ytterbium or lutetium,” J. Am. Ceram. Soc. 65, c168–c171 (1982).
[Crossref]

Fan, H.

G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009).
[Crossref]

Fan, S.

K. Li, Q. Zhang, S. Fan, L. Zhang, J. Zhang, and L. Hu, “Mid-infrared luminescence and energy transfer characteristics of Ho3+/Yb3+codoped lanthanum-tungsten-tellurite glasses,” Opt. Mater. 33, 31–35 (2010).
[Crossref]

G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009).
[Crossref]

Fan, W.

W. Fan, L. Htein, B. H. Kim, P. R. Watekar, and W. T. Han, “Upconversion luminescence in bismuth-doped germane-silicate glass optical fiber,” Opt. Laser Technol. 54, 376–379 (2013).
[Crossref]

Fanelli, E.

A. Aronne, V. N. Sigaev, B. Champagnon, E. Fanelli, V. Califano, L. Z. Usmanova, and P. Pernice, “The origin of nanostructuring in potassium niobiosilicate glasses by Raman and FTIR spectroscopy,” J. Non-Cryst. Solids 351, 3610–3618 (2005).
[Crossref]

Feng, S.

G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009).
[Crossref]

L. Yi, M. Wang, S. Feng, Y. Chen, G. Wang, L. Hu, and J. Zhang, “Emission properties of Ho3+: 5I7 → 5I8 transition sensitized by Er3+ and Yb3+ in fluorophosphates glasses,” Opt. Mater. 31, 1586–1590 (2009).
[Crossref]

Ferrari, M.

L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007).
[Crossref]

Fortes, L. M.

L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007).
[Crossref]

Fukumi, K.

K. Fukumi and S. Sakka, “Coordination state of Nb5+ ions in silicate and gallate glasses as studied by Raman spectroscopy,” J. Mater. Sci. 23, 2819–2823 (1988).
[Crossref]

Gao, G.

G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009).
[Crossref]

Girard, S.

A. Braud, S. Girard, J. L. Doualan, M. Thuau, and R. Moncorgé, “Energy-transfer processes in Yb:Tm-doped KY3F10, LiYF4, and BaY2F8 single crystals for laser operation at 1.5 and 2.3  μm,” Phys. Rev. B. 61, 5280–5292 (2000).
[Crossref]

Goncalves, M. C.

L. M. Fortes, L. F. Santos, M. C. Goncalves, R. M. Almeida, M. Mattarelli, M. Montagna, A. Chiasera, M. Ferrari, A. Monteil, S. Chaussedent, and G. C. Righini, “Er3+ ion dispersion in tellurite oxychloride glasses,” Opt. Mater. 29, 503–509 (2007).
[Crossref]

Guo, Y.

M. Li, X. Liu, Y. Guo, L. Hu, and J. Zhang, “Energy transfer characteristics of silicate glass doped with Er3+, Tm3+, and Ho3+ for 2  μm emission,” J. Appl. Phys. 114, 243501 (2013).
[Crossref]

M. Li, G. Bai, Y. Guo, L. Hu, and J. Zhang, “Investigation on Tm3+-doped silicate glass for 1.8  μm emission,” J. Lumin. 132, 1830–1835 (2012).
[Crossref]

Han, W. T.

W. Fan, L. Htein, B. H. Kim, P. R. Watekar, and W. T. Han, “Upconversion luminescence in bismuth-doped germane-silicate glass optical fiber,” Opt. Laser Technol. 54, 376–379 (2013).
[Crossref]

Haub, J.

Hemming, A.

Henderson, G. S.

G. S. Henderson, D. R. Neuville, B. Cochain, and L. Cormier, “The structure of GeO2-SiO2 glasses and melts: A Raman spectroscopy study,” J. Non-Cryst. Solids 355, 468–474 (2009).
[Crossref]

Heo, J.

B. S. Yong, H. T. Lim, Y. G. Choi, Y. S. Kim, and J. Heo, “2.0  μm emission properties and energy transfer between Ho3+ and Tm3+ in PbO-Bi2O3-Ga2O3 glasses,” J. Am. Ceram. Soc. 83, 787–791 (2000).

Heumann, E.

K. Scholle, E. Heumann, and G. Huber, “Single mode tm and Tm, Ho: LuAG lasers for LIDAR applications,” Laser Phys. Lett. 1, 285–290 (2004).
[Crossref]

Hruby, A.

A. Hruby, “Evaluation of glass-forming tendency by means of DTA,” J. Phys. B 22, 1187–1193 (1972).

Htein, L.

W. Fan, L. Htein, B. H. Kim, P. R. Watekar, and W. T. Han, “Upconversion luminescence in bismuth-doped germane-silicate glass optical fiber,” Opt. Laser Technol. 54, 376–379 (2013).
[Crossref]

Hu, L.

T. Xue, L. Zhang, L. Wen, M. Liao, and L. Hu, “Er3+ doped fluorogallate glass for mid-infrared applications,” Chin. Opt. Lett. 13, 081602 (2015).
[Crossref]

F. Huang, X. Liu, W. Li, L. Hu, and D. Chen, “Energy transfer mechanism in Er3+ doped fluoride glass sensitized by Tm3+ or Ho3+ for 2.7  μm emission,” Chin. Opt. Lett. 12, 051601 (2014).
[Crossref]

M. Li, X. Liu, Y. Guo, L. Hu, and J. Zhang, “Energy transfer characteristics of silicate glass doped with Er3+, Tm3+, and Ho3+ for 2  μm emission,” J. Appl. Phys. 114, 243501 (2013).
[Crossref]

X. Li, X. Liu, L. Zhang, L. Hu, and J. Zhang, “Emission enhancement in Er3+/Pr3+-codoped germanate glasses and their use as a 2.7  μm laser material,” Chin. Opt. Lett. 11, 121601 (2013).
[Crossref]

G. Bai, L. Tao, K. Li, L. Hu, and Y. H. Tsang, “Enhanced light emission near 2.7  μm from Er-Nd co-doped germanate glass,” Opt. Mater. 35, 1247–1250 (2013).
[Crossref]

M. Li, G. Bai, Y. Guo, L. Hu, and J. Zhang, “Investigation on Tm3+-doped silicate glass for 1.8  μm emission,” J. Lumin. 132, 1830–1835 (2012).
[Crossref]

J. Ding, G. Zhao, Y. Tian, W. Chen, and L. Hu, “Bismuth silicate glass: a new choice for 2  μm fiber lasers,” Opt. Mater. 35, 85–88 (2012).
[Crossref]

R. Xu, M. Wang, Y. Tian, L. Hu, and J. Zhang, “2.05  μm emission properties and energy transfer mechanism of germanate glass doped with Ho3+, Tm3+, and Er3+,” J. Appl. Phys. 109, 053503 (2011).
[Crossref]

R. Xu, Y. Tian, L. Hu, and J. Zhang, “Structural origin and energy transfer processes of 1.8  μm emission in Tm3+ doped germanate glasses,” J. Phys. Chem. A. 115, 6488–6492 (2011).
[Crossref]

R. Xu, Y. Tian, L. Hu, and J. Zhang, “Broadband 2  μm emission and energy-transfer properties of thulium-doped oxyfluoride germanate glass fiber,” Appl. Phys. B 104, 839–844 (2011).
[Crossref]

K. Li, Q. Zhang, S. Fan, L. Zhang, J. Zhang, and L. Hu, “Mid-infrared luminescence and energy transfer characteristics of Ho3+/Yb3+codoped lanthanum-tungsten-tellurite glasses,” Opt. Mater. 33, 31–35 (2010).
[Crossref]

M. Wang, L. Yi, G. Wang, L. Hu, and J. Zhang, “Emission performance in Ho3+ doped fluorophosphates glasses sensitized with Er3+ and Tm3+ under 800  nm excitation,” Solid State Commun. 149, 1216–1220 (2009).
[Crossref]

L. Yi, M. Wang, S. Feng, Y. Chen, G. Wang, L. Hu, and J. Zhang, “Emission properties of Ho3+: 5I7 → 5I8 transition sensitized by Er3+ and Yb3+ in fluorophosphates glasses,” Opt. Mater. 31, 1586–1590 (2009).
[Crossref]

G. Gao, L. Hu, H. Fan, G. Wang, K. Li, S. Feng, S. Fan, H. Chen, J. Pan, and J. Zhang, “Investigation of 2.0  μm emission in Tm3+ and Ho3+ co-doped TeO2-ZnO-Bi2O3 glasses,” Opt. Mater. 32, 402–405 (2009).
[Crossref]

Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Thermal analysis and optical transition of Yb3+, Er3+ co-doped lead-germanium-tellurite glasses,” J. Mater. Res. 19, 1630–1637 (2004).
[Crossref]

Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Thermal analysis and optical properties of Yb3+/Er3+codoped oxyfluoride germanate glasses,” J. Opt. Soc. Am. B 21, 951–957 (2004).
[Crossref]

Z. Yang, S. Xu, L. Hu, and Z. Jiang, “Density of Na2O-(3-x)SiO2-xGeO2 glasses related to structure,” Mater. Res. Bull. 39, 217–222 (2004).
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L. Kong, G. Xie, P. Yuan, L. Qian, S. Wang, H. Yu, and H. Zhang, “Passive Q-switching and Q-switched mode-locking operations of 2  μm Tm:CLNGG laser with MoS2 saturable absorber mirror,” Photo. Res. 3, A47–A50 (2015).
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Zhang, H.

L. Kong, G. Xie, P. Yuan, L. Qian, S. Wang, H. Yu, and H. Zhang, “Passive Q-switching and Q-switched mode-locking operations of 2  μm Tm:CLNGG laser with MoS2 saturable absorber mirror,” Photo. Res. 3, A47–A50 (2015).
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M. Li, X. Liu, Y. Guo, L. Hu, and J. Zhang, “Energy transfer characteristics of silicate glass doped with Er3+, Tm3+, and Ho3+ for 2  μm emission,” J. Appl. Phys. 114, 243501 (2013).
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[Crossref]

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Figures (6)

Fig. 1.
Fig. 1. Deconvolution of Raman spectrum of SG glass using symmetric Gaussian functions.
Fig. 2.
Fig. 2. Absorption spectra of Tm 3 + single-doped and Tm 3 + / Ho 3 + co-doped silicate-germanate glasses in the range of 400–2200 nm.
Fig. 3.
Fig. 3. Fluorescence spectra of the Tm 3 + / Ho 3 + co-doped silicate-germanate glasses.
Fig. 4.
Fig. 4. Energy level diagrams and energy transfer sketch map of Tm 3 + and Ho 3 + ions.
Fig. 5.
Fig. 5. Emission cross sections of silicate-germanate glasses doped with 1.5 mol% Tm 2 O 3 and 1 mol% Ho 2 O 3 .
Fig. 6.
Fig. 6. (a) Fluorescence decay curve of Tm 3 + / Ho 3 + co-doped glass sample from Tm 3 + : F 4 3 H 6 3 . Inset shows the decay curve of Tm 3 + singly doped glass sample. (b) Fluorescence decay curve of Tm 3 + / Ho 3 + co-doped glass samples from Ho 3 + : I 7 5 I 8 5 .

Tables (5)

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Table 1. Compositions of the Prepared Glasses

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Table 2. Physical and Thermal Properties of Silicate-Germanate Glasses

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Table 3. J-O intensity Parameters ( Ω λ , λ = 2 , 4, 6) ( × 10 20    cm 2 ) of Ho 3 + Ions in Various Glass Hosts

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Table 4. Spontaneous Transition Probability A rad , Branching Ratio β , and Radiative Lifetime τ rad for Different Excited Levels of Ho 3 + in Silicate-Germanate Glass

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Table 5. Peak Cross Section σ e peak , FWHM, Radiative Lifetime τ m , σ e peak × FWHM and σ e peak × τ m of I 7 5 I 8 5 Transition of Ho 3 + in Different Glass Samples

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

H 6 3 ( Tm 3 + ) + h v ( 808    nm ) H 4 3 ( Tm 3 + )    ( GSA ) H 4 3 ( Tm 3 + ) + H 6 3 ( Tm 3 + ) F 4 3 ( Tm 3 + ) + F 4 3 ( Tm 3 + )    ( CR ) F 4 3 ( Tm 3 + ) H 6 3 ( Tm 3 + ) + h v ( 1.8    μm )    ( emission ) F 4 3 ( Tm 3 + ) + I 8 5 ( Ho 3 + ) H 6 3 ( Tm 3 + ) + I 7 5 ( Ho 3 + )    ( ET ) I 7 5 ( Ho 3 + ) I 8 5 ( Ho 3 + ) + h v ( 2    μm )    ( emission )
σ em ( λ ) = σ abs ( λ ) × Z l Z u × exp [ h c k T × ( 1 λ Z L 1 λ ) ] ,
σ abs ( λ ) = 2.303 log ( I 0 / I ) N l ,
σ em ( λ ) = λ 4 A rad 8 π c n 2 × λ I ( λ ) λ I ( λ ) d λ ,
η = 1 τ Tm / Ho τ Tm .
W ET = 1 τ Tm / Ho 1 τ Tm ,
Q.E. = τ obs τ rad ,

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