Comparative study of 2.7 &#x03BC;m emission of Ho<sup>3+</sup> desensitized Er<sup>3+</sup> in tellurite and bismuth glass

Guoying Zhao; Wentian Jin; Yongzheng Fang; Yubiao He; Yingjie Li; Yufeng Liu; Meisong Liao; Jun Zou

doi:10.1364/OME.7.001147

1. Introduction

The 2.7 μm mid-infrared luminescence of the Er³⁺ ion is very useful for infrared countermeasures as well as in medical surgery owing to the electronic transitions ⁴I_11/2 → ⁴I_13/2 [1–3]. A highly doped Er³⁺ concentration is preferred for the energy recycling of the ⁴I_11/2 level and the fast depletion of the ⁴I_13/2 level [4]. Meanwhile, a suitable codoping of rare earth ions is required to provide a high population inversion. It has been reported that Ho³⁺ ions can deplete upper-level ⁴I_11/2 and terminal-level ⁴I_13/2 as a deactivator. An enhanced 2.7 μm emission was obtained from Er³⁺/Ho³⁺ codoped fluorophosphate glass (FP) using ZBYA glass in the literature [5,6]. However, the opposite results were also observed for Er³⁺/Ho³⁺ codoped fluorophosphate [4]. Therefore, the compositional dependence of the energy transfer mechanism between Er³⁺ and Ho³⁺ must be further examined.

Unlike the desensitizer Pr³⁺ and Nd³⁺ ions, Ho³⁺ depletes the population on the energy level, assisted by a phonon-involved energy transfer. Thus, the phonon energy distribution of the host glass has a strong influence on the fluorescence behavior of Er³⁺and Ho³⁺ ions. With regard to 2–3 μm lasers, research interest has been focused mainly on low-phonon energy glass, such as fluoride and chalcogenide glass, owing to the small energy gaps between the Er³⁺:⁴I_11/2 and ⁴I_13/2 levels [7–9]. In addition, fluorophosphate with a small amount of phosphate could yield a quantum efficiency that promotes the 2.7 μm transition positively [5]. Chalcogenide glass is characterized by its wide infrared transparency and high refractive index, which makes it a natural candidate for infrared lasers [10, 11]. However, its complicated preparation and processing, and its inferior thermal stability, restrict it from wide application. Fluoride glass possesses the high solubility of rare earth ions, has wide infrared transparency, and can be easily prepared using the melt-quenching method [12]. Unfortunately, fluoride glass suffers from poor chemical stability.

Heavy metal oxide (HMO) glass is a promising host glass owing to its special properties such as a high refractive index, high density, and excellent infrared transmission [13, 14]. Tellurite and bismuth glass are the most important types of HMO glass. The difference in phonon distribution of tellurite and bismuth glass has a great influence on the phonon-assisted energy transfer processes between Er³⁺ and Ho³⁺ ions. Based on these qualities, two series of Er³⁺-doped and Er³⁺/Ho³⁺ codoped tellurite and bismuth glass were prepared and characterized to investigate the effect of Ho³⁺ on Er³⁺:2.7 μm fluorescence in HMO glass. The Judd–Ofelt theory and the Dexter model are employed to quantitatively examine the kinetic behaviors between the excited levels.

2. Experimental

The set of glass used in this paper has the following nominal molar composition: 54TeO₂ - 31WO_1.5 - 15LaO_1.5 - 2ErO_1.5 - xHoO_1.5 (x = 0, 2); 55BiO_1.5 - 30GeO₂ - 15NaO_0.5 - 2ErO_1.5 - xHoO_1.5 (x = 0, 2), henceforth called TWLE, TWLEH, BGNE, and BGNEH, respectively. The undoped tellurite and bismuth glass matrices are denoted as TWL and BGN, respectively. The raw materials were prepared from high-purity TeO₂, W₂O₃, La₂O₃, Bi₂O₃, GeO₂, Na₂CO₃, and Er₂O₃ and Ho₂O₃ powder. Well-mixed raw materials (30 g) were placed in an alumina crucible and melted at 1050°C for 30 min in an oxygen atmosphere. Bubbling dry oxygen gas in melt was used to minimize the hydroxyl groups. The melts were quickly poured into preheated stainless-steel molds and annealed for 2 h near the glass transition temperature (T_g). The annealed sample was fabricated and polished to a size of 20 × 10 × 1 mm³ for optical property measurements.

Refractive indices were detected at room temperature using a Metricon Model 2010/M Prism Coupler. The Raman spectra of the glasses were measured with a Renishaw InVia Raman spectrophotometer using the 488-nm excitation line from a spectra physics laser. The absorption spectra were recorded with a Perkin-Elmer Lambda 900UV/VIS/NIR spectrophotometer in 1-nm steps. The fluorescence spectra were measured by a TRIAX550 spectrophotometer with a 980-nm LD as an excitation source. All measurements were conducted at room temperature.

3. Results and discussion

3.1 Raman spectra

The Raman spectra of the TWL and BGN samples are depicted in Fig. 1. The glass network structure could be effectively understood by the Raman scattering. Furthermore, the arrangement of the phonon energy of the host glass system can be evaluated from Raman spectroscopy. As shown in Fig. 1, the most prominent band at 780 cm⁻¹ of TWL pure glass comprises the combined vibrations of asymmetric stretching and symmetric stretching of TeO₄ trigonal bipyramid (tbp), and stretching vibrations of nonbridging Te-O^– bands in the TeO₃ trigonal pyramid (tp) [15, 16]. The wide band at 345 cm⁻¹ is associated with the vibration of TeO₃ tp [17]. With regard to the BGN glass, the Raman spectrum is dominated by an intense and broad band at 384 cm⁻¹, which arises from the vibrations of Bi-O-Bi symmetric stretching of [BiO₃] pyramidal units and [BiO₆] octahedral units [18,19]. By contrast, the phonon density at a higher frequency range of TWL glass is larger than that of BGN glass, which may increase the probability rate of nonradiative relaxation by multiphonon relaxation.

Fig. 1 Raman spectra of TWL and BGN samples.

Download Full Size | PDF

3.2 Absorption spectra and Judd–Ofelt analysis

Absorption spectra were obtained for Er³⁺ single-doped and Er³⁺/Ho³⁺ codoped tellurite and bismuth glass in the 400–2200 nm range (Fig. 2). The absorption bands correspond to the 4f-4f optical excitations assigned to the transitions from the ground state to the higher states of Er³⁺ and Ho³⁺ ions. These are indicated in the figure. As observed in Fig. 2, the absorption cut edge shifted to the ultraviolet range for TWL with respect to BGN. This is associated with the higher polarizability of the Te⁴⁺ ions (α_Bi = 1.508 × 10⁻³ nm³, α_Te = 1.595 × 10⁻³ nm³) [20]. By comparison, there is no obvious difference in the position and shape of the absorption bands between the single and codoped glasses.

Fig. 2 Absorption spectra of prepared samples (1 mm thickness).

Download Full Size | PDF

In order to further examine spectroscopic variations of Er³⁺, the Judd–Ofelt (simplified as J-O) theory is employed to evaluate radiative properties such as the spontaneous transition probability (A_rad), branching ratio (β), and radiative lifetime (τ_R) of excited levels of Er³⁺ in the single and codoped samples [21, 22]. These values are listed in Table 1. The theory and detailed calculation procedure were described in earlier literature [23]. The parameters Ω₂ and Ω₄ are widely studied in literature [24]. Ω₂ is sensitive to the covalence of chemical bonding around the RE ion and the ligand asymmetry of the local environment of the host glass, while Ω₆ is of particular interest since this parameter affects the values of the calculated spontaneous emission probabilities for the electronic transitions of RE³⁺ ions [25–28]. As shown in Table 1, the calculated Ω₂ for TWL glass is lower than that for BGN glass. This may be caused by the weaker covalence of the Bi-O^- bond compared with the Te-O^- bond. A higher magnitude of Ω₆ in bismuth glass entirely favors the larger transition ability. Therefore, owing to the higher Ω₂ and Ω₆, it is reasonable that the spontaneous transition probability (A_rad) of Er³⁺ transitions for BGN glass is higher than that for TWL glass, as listed in Table 1.

Table 1. J-O intensity parameters Ω_λ, spontaneous radiative transition probability (A_rad), fluorescence branching ratios (β), and radiative lifetime (τ_R) of excited levels of Er³⁺ in single and codoped samples.

View Table | View all tables in this article

After the introduction of the codoped Ho³⁺, Ω₂, Ω₆, A_rad, and τ_R show considerable variations in the codoped sample. This indicates that the addition of Ho³⁺ has an important influence on the local surroundings of Er³⁺. A_rad of the Er³⁺:⁴I_11/2 → ⁴I_13/2 transition increases from 56.04 s⁻¹ to 74.89 s⁻¹ in tellurite glass. A similar trend occurs for bismuth glass. This is derived from a partial population transfer from Er³⁺:⁴I_13/2 to Ho³⁺:⁵I₇ (shown in Fig. 6). On the other hand, the values of τ_R corresponding to the Er³⁺:⁴I_13/2 → ⁴I_15/2 transition in codoped samples are lower than those for single-doped samples. This results from the consumption of the population of Er³⁺:⁴I_13/2 to Ho³⁺:⁵I₇ based on the desensitized effect of Ho³⁺. This predicts the lower fluorescence intensity at 1.5 μm in the codoped samples. Interestingly, the branching ratio β of the Er³⁺:⁴I_11/2 → ⁴I_13/2 transition is about 19% for TWL and 15% for BGN, and decreases moderately after the introduction of the desensitizer Ho³⁺. This trend is different from that of FP and ZBAY [4, 29]. If an additional nonradiative feeding route does not exist, only portions of less than one fifth of the total population of ⁴I_11/2 are radiatively fed to the ⁴I_13/2 level. This has a detrimental effect on the 2.7 μm fluorescence.

3.3 Photoluminescence spectra and energy transfer process

Under the excitation of a 980 nm laser diode, the fluorescence spectra from 2550 nm to 2850 nm of Er³⁺ single-doped samples and Er³⁺/ Ho³⁺ codoped samples are depicted in Fig. 3. The emission band around 2.7 μm assigned to the Er³⁺:⁴I_11/2 → ⁴I_13/2 transition increases significantly with the introduction of Ho³⁺; however, the opposite phenomenon was observed in the BGNEH samples. These results suggest a great discrepancy between the phonon-assisted energy transfer mechanisms of tellurite and bismuth glass.

Fig. 3 Mid-infrared fluorescence spectra of samples pumped by 980 nm laser diode.

Download Full Size | PDF

According to the Fuchtbauer–Ladenburg theory and emission spectra, the 2.7 μm emission cross section (σ_em) can be calculated using the following equation [30, 31]:

σ_{e m} = \frac{λ^{4} A_{r a d}}{8 π c n^{2}} \times \frac{λ I (λ)}{\int λ I (λ) d λ},

where λ represents the wavelength, A_rad represents the spontaneous transition probability corresponding to the Er³⁺:⁴I_11/2 → ⁴I_13/2 transition, I(λ) is the emission intensity, and c and n are the light speed in a vacuum and the refractive index of glass, respectively. The maximum of the emission cross section in the TWLEH glass at 2.7 μm reaches 11.4 × 10⁻²¹ cm², which is higher than that of Er³⁺/Ho³⁺ codoped ZBYA (10.2 × 10⁻²¹ cm²) or ZBLAY (10.8 × 10⁻²¹ cm²) [6, 8]. A high σ_em is beneficial to obtaining a laser action. This suggest that Er³⁺/Ho³⁺ codoped TWL glass might be a promising candidate for a mid-infrared laser system.

In order to explore the energy transfer mechanisms of tellurite and bismuth glass, the fluorescence spectra ranging from 1300 nm to 2200 nm and the visual upconversion spectra were measured and shown in Fig. 4 and Fig. 5, respectively.

Fig. 4 Measured fluorescence spectrum of samples from 1300 nm to 2200 nm pumped at 980 nm.

Download Full Size | PDF

Fig. 5 Upconversion luminescence spectra of samples under 980 nm LD excitation.

Download Full Size | PDF

In Fig. 4, two obvious emission bands at 1.53 μm and 2.02 μm are attributed to the Er³⁺:⁴I_13/2 → ⁴I_15/2 transition and Ho³⁺: ⁵I₇ → ⁵I₈ transition, respectively. Since Ho³⁺ cannot be pumped efficiently by 980 nm LD, the emergence of a 2.02 μm emission accompanied by a descending 1.53 μm emission gives evidence to the energy transfer from Er³⁺ to Ho³⁺. Note that the intensity ratio of the 1.53 μm emission from codoped glass to single-doped glass (C/S) in tellurite glass (9.2%) is larger than that in bismuth glass (2.6%). The remaining 2.6% 1.5 μm emission intensity in bismuth glass indicates a more efficient energy transfer from Er³⁺:⁴I_13/2 to Ho³⁺. This ratio is helpful in estimating the discrepancies between the energy transfer mechanisms of Er³⁺ and Ho³⁺ in different glass hosts. It is noted that the 1.5μm emission intensity was found almost two times larger in tellurite glass than in bismuth glass, indicating the more energy resided in the Er³⁺:⁴I_11/2 level are transferred to Ho³⁺ in tellurite glass.

Under excitation of a 980 nm LD, the visual upconversion emission spectra of the samples are shown in Fig. 5. The spectra contain two intense bands in the green and red regions. Each assignment corresponding to the 4f-4f electronic transition is labeled for the present case. Owing to the incorporation of the Ho³⁺:⁵F₄, ⁵S₂ → ⁵I₈ and Ho³⁺:⁵F₅ → ⁵I₈ transitions, the emission band around 550 nm generally shifts to the longer-wavelength side, while the 670 nm emission band shifts toward the shorter-wavelength side. With regard to the emission intensity, a weaker green emission and a stronger red emission are observed after the introduction of Ho³⁺ in the codoped samples, which is different from that of FP glass but similar to that of ZBYA glass [5, 29]. It is worthwhile to trace the differences in the spectral features of the two glasses. The C/S intensity ratios of the 550 nm emission and 670 nm emission in tellurite glass are larger than those in bismuth glass. This is depicted in Fig. 5.

On the basis of the above analysis, the details of the energy transfer channels between Er³⁺ and Ho³⁺ are shown in Fig. 6. For the Er³⁺ single-doped sample, the green and red emission bands correspond to the ⁴F_7/2, ²H_11/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2 transitions, while the 2.7 μm emission contributes to the ⁴I_11/2 → ⁴I_13/2 transition [29, 32]. After the introduction of Ho³⁺, owing to the small energy gap, some particles in Er³⁺:²H_11/2 and Er³⁺:⁴S_3/2 are transferred to Ho³⁺:⁵F₄ and Ho³⁺:⁵S₂, respectively, then nonradiatively de-excite to Ho³⁺:⁵F₅, yielding the red emission. The energy transfer process can explain the wavelength shift of the upconversion luminescence peaks in the codoped samples. This is also responsible for the weaker green emission and stronger red emission in the codoped samples. According to the enhanced 2.0 μm emission and reduced 1.5 μm emission, there exists a shortcut from Er³⁺:²H_13/2 to Ho³⁺:⁵I₇. Similarly, a fraction of Er³⁺:²H_11/2 excitation can be transferred to Ho³⁺:⁵I₆, which has a significant influence on the 2.7 μm emission. It is noted that some phonons are needed to assist the two energy transfer processes in hosts.

Fig. 6 Energy level diagram of Er³⁺ and Ho³⁺ ions with involved energy transfer mechanism.

Download Full Size | PDF

Except for direct energy transfers, the interactions between ions at higher concentrations contain cross-relaxation channels. Two main cross-relaxation processes are considered to be responsible for the luminescence quenching and shorter lifetimes [33]. On the one hand, energy on the Er³⁺:⁴I_11/2 level can be transferred to the Ho³⁺:⁵I₆ level, resulting an increase in populations on the Ho³⁺:⁵F₄ level. On the other hand, the Ho³⁺:⁵F₅ level could be populated through the cross relaxation if the Ho³⁺:⁵I₆ level absorbs the energy stored on the Er³⁺:⁴I_11/2 level.

The main energy transfer processes under excitation at 980 nm are as follows:

{Er}^{3 +} :^{2} H_{11 / 2} + {Ho}^{3 +} :^{5} I_{8} \to {Er}^{3 +} :^{4} I_{15 / 2} + {Ho}^{3 +} :^{5} F_{4}

{Er}^{3 +} :^{4} S_{3 / 2} + {Ho}^{3 +} :^{5} I_{8} \to {Er}^{3 +} :^{4} I_{15 / 2} + {Ho}^{3 +} :^{5} S_{2}

{Er}^{3 +} :^{4} I_{11 / 2} + {Ho}^{3 +} :^{5} I_{8} \to {Er}^{3 +} :^{4} I_{15 / 2} + {Ho}^{3 +} :^{5} I_{6}

{Er}^{3 +} :^{4} I_{13 / 2} + {Ho}^{3 +} :^{5} I_{8} \to {Er}^{3 +} :^{4} I_{15 / 2} + {Ho}^{3 +} :^{5} I_{7}

{Er}^{3 +} :^{4} I_{11 / 2} + {Ho}^{3 +} :^{5} I_{6} \to {Er}^{3 +} :^{4} I_{15 / 2} + {Ho}^{3 +} :^{5} F_{4}

{Er}^{3 +} :^{4} I_{13 / 2} + {Ho}^{3 +} :^{5} I_{6} \to {Er}^{3 +} :^{4} I_{15 / 2} + {Ho}^{3 +} :^{5} F_{5}

For the case of an almost resonant transfer, ET1 and ET2, few phonons are needed to assist the processes in hosts. The energy of the Er³⁺:²H_11/2 and Er³⁺:⁴S_3/2 levels are transferred to the Ho³⁺:⁵F₄ and Ho³⁺:⁵S₂ levels, respectively, resulting in a weaker green emission and a wavelength shift to the shorter sideband. The CR1 process can feed the population on the Ho³⁺:⁵F₄ level, consuming the energy of the upper level corresponding to the 2.7 μm emission. There is energy competition between the transition luminescence of the Er³⁺:⁴I_11/2 level and energy transfer processes ET1, ET2, and CR1 in glass. The observed weaker green emission in the codoped BGN glass (C/S = 0.22) in Fig. 5 proves that the energy transfer from the Er³⁺:⁴I_11/2 level to the Ho³⁺ level is more efficient than that in TWL glass (C/S = 0.42). It is noted that the green emission intensity was found almost 40 times larger in tellurite glass than in bismuth glass.

On the other hand, benefiting from the ET3 and ET4 process, a 2.0 μm emission assigned to the Ho³⁺:⁵I₇ → ⁵I₈ transition is enhanced at the expense of the decreased 1.5 μm emission of Er³⁺. For the energy stored on the Er³⁺:²H_13/2 level, there are two channels for population feeding from the Er³⁺:²H_13/2 level to Ho³⁺: ET4 and CR2. The reduction in the 1.5 μm emission intensity is accompanied by an enhanced 2.0 μm emission and red upconversion emission. Furthermore, comparing the C/S intensity ratio of the 1.5 μm emission and the red upconversion emission in tellurite and bismuth glass, it is found that the population density of the Er³⁺:²H_13/2 level is drastically reduced in tellurite glass.

According to Dexter and Förster, the microscopic constants of phonon-assisted energy transfer processes ET3 and ET4 can be determined [34, 35]. The related calculation methods were described in the literature [36]. The energy transfer microparameters of the above two processes are listed in Table 2. The N-phonon contribution terms (%) to the total probability rates are also listed. The results prove that the ET4 process is more effective than the ET3 process in the two systems, which are favorable to a population inversion between the upper Er³⁺:⁴I_11/2 level and the lower Er³⁺:⁴I_13/2 level. In addition, the forward energy transfer microparameters C_DA of the ET4 process in tellurite glass is 11.89 × 10⁻⁴⁰cm⁶/s. This is higher than that in bismuth glass, indicating that the ~2.7 μm Er³⁺:⁴I_13/2 lower level is depopulated drastically. At least three phonons in bismuth glass are needed to assist the ET4 process, implying that this process barely takes place in the BGN samples [37, 38].

Table 2. Calculated microparameters C_DA, C_AD for the two Er³⁺ → Ho³⁺ energy transfer processes (ET3 and ET4). Number (#) of phonons needed to assist energy transfer, as well as the percentage of each phonon participation (%) in the process.

View Table | View all tables in this article

In summary, two facts may be responsible for the discrepancies of the 2.7 μm spectroscopic properties in tellurite and bismuth glass. First, through the three processes ET1, ET2, and CR1, the energy stored on the Er³⁺:⁴I_11/2 level is transferred efficiently to the excited states of Ho³⁺ in bismuth glass. Second, the ET4 process has a very harmful impact on the population of the Er³⁺:⁴I_13/2 level, resulting in a strong population inversion in tellurite glass.

4. Conclusions

Based on a description of visual, near-infrared, and mid-infrared spectroscopic properties in Er³⁺/Ho³⁺ codoped tellurite and bismuth glass, some conclusions have been derived to understand the energy interaction between Er³⁺ and Ho³⁺ ions. Meanwhile, the radiative properties of RE³⁺ in heavy metal oxide glass were quantitatively analyzed using the Judd–Ofelt theory and Dexter–Förster model. The results demonstrate that the Ho³⁺ desensitization effect on the Er³⁺:2.7 μm fluorescence exhibits a great discrepancy between the tellurite and bismuth glass matrices. In particular, the Er³⁺:2.7 μm mid-infrared emission is characterized by a higher spontaneous transition probability (74.89 s⁻¹) and larger calculated emission cross section (11.4 × 10⁻²¹cm²) in the TWLEH sample. The codoping introduction of Ho³⁺ depresses the Er³⁺:2.7 μm emission in bismuth glass. According to the Judd–Ofelt theory, the spontaneous transition probability of the Er³⁺:⁴I_11/2 → ⁴I_13/2 transition corresponding to the 2.7 μm emission increases after Ho³⁺ codoping in the two systems. By comparing the ratios of integrated emission intensity in the codoped doped sample to those of the single-doped sample, it is found that green emissions are decreased drastically in bismuth glass, while the increase of red emissions are relatively weak. For the nonresonant energy transfer mechanism between the Er³⁺ and Ho³⁺ ions, the phonon energy distribution of the glass host plays an important role. Benefiting from its relatively high phonon energy, tellurite glass has a larger energy transfer microparameter for the Er³⁺:⁴I_13/2 → Ho³⁺:⁵I₇ transition, which promotes the 2.7 μm emission.

Funding

National Natural Science Foundation of China (NSFC) (No. 61605115, 51472162); Shanghai Sailing Project (No.15YF1411800); Program for the Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (No. TP2014061).

References and links

1. G. Wu, S. Fan, Y. Zhang, G. Chai, Z. Ma, M. Peng, J. Qiu, and G. Dong, “2.7 μm emission in Er³⁺:CaF₂ nanocrystals embedded oxyfluoride glass ceramics,” Opt. Lett. 38(16), 3071–3074 (2013). [CrossRef] [PubMed]

2. G. Chai, G. Dong, J. Qiu, Q. Zhang, and Z. Yang, “2.7 μm emission from transparent Er³⁺,Tm³⁺ codoped yttrium aluminum garnet (Y₃Al₅O₁₂) nanocrystals–tellurate glass composites by novel comelting technology,” J. Phys. Chem. C 116(37), 19941–19950 (2012). [CrossRef]

3. M. Peng and L. Wondraczek, “Photoluminescence of Sr₂P₂O₇:Bi²⁺ as a red phosphor for additive light generation,” Opt. Lett. 35(15), 2544–2546 (2010). [CrossRef] [PubMed]

4. L. Zhang and T. Xue, “Discrepancies between Pr³⁺ and Ho³⁺ de-sensitized Er³⁺:2.7 μm emission,” J. Lumin. 178, 22–26 (2016). [CrossRef]

5. L. Zhang, Z. Yang, Y. Tian, J. Zhang, and L. Hu, “Comparative investigation on the 2.7 μm emission in Er³⁺/Ho³⁺ codoped fluorophosphate glass,” J. Appl. Phys. 110(9), 093106 (2011). [CrossRef]

6. F. Huang, X. Liu, Y. Zhang, L. Hu, and D. Chen, “Enhanced 2.7- and 2.84-μm emissions from diode-pumped Ho³⁺/Er³⁺-doped fluoride glass,” Opt. Lett. 39(20), 5917–5920 (2014). [CrossRef] [PubMed]

7. H. Guo, L. Liu, Y. Wang, C. Hou, W. Li, M. Lu, K. Zou, and B. Peng, “Host dependence of spectroscopic properties of Dy ³⁺ - doped and Dy ³⁺, Tm ³⁺ -codped Ge-Ga-S-CdI ₂ chalcohalide glasses,” Opt. Express 17(17), 15350–15358 (2009). [CrossRef] [PubMed]

8. Y. Tian, T. Wei, X. Jing, J. Zhang, and S. Xu, “Enhanced 2.7- and 2.9-μm emissions in Er³⁺/Ho³⁺ doped fluoride glasses sensitized by Pr³⁺ ions,” Mater. Res. Bull. 76, 67–71 (2016). [CrossRef]

9. P. Kuan, X. Fan, W. Li, X. Liu, C. Yu, L. Zhang, and L. Hu, “High-efficiency ∼2 μm laser in a single-mode Tm-doped lead germanate composite fiber,” Chin. Opt. Lett. 14(8), 081601 (2016). [CrossRef]

10. Y. Yang, Z. Yang, P. Lucas, Y. Wang, Z. Yang, A. Yang, B. Zhang, and H. Tao, “Composition dependence of physical and optical properties in Ge-As-S chalcogenide glasses,” J. Non-Cryst. Solids 440, 38–42 (2016). [CrossRef]

11. Z. Li, T. Xu, X. Shen, S. Dai, X. Wang, Q. Nie, and X. Zhang, “Investigation of 2.9 μm luminescence properties and energy transfer in Tm³⁺/Dy³⁺ co-doped chalcohalide glasses,” J. Rare Earths 29(2), 105–108 (2011). [CrossRef]

12. T. Hu, D. D. Hudson, and S. D. Jackson, “Actively Q-switched 2.9 μm Ho³⁺Pr³⁺-doped fluoride fiber laser,” Opt. Lett. 37(11), 2145–2147 (2012). [CrossRef] [PubMed]

13. G. Zhao, Y. Tian, H. Fan, J. Zhang, and L. Hu, “Efficient 2.7μm emission in Er³⁺-doped bismuth germanate glass pumped by 980-nm laser diode,” Chin. Opt. Lett. 10(9), 091601 (2012). [CrossRef]

14. S. C. Ardelean, R. C. Lucacel, and O. Hulpus, “EPR and FT-IR spectroscopic studies of B₂O₃Bi₂O₃MnO glasses,” Solid State Sci. 7(11), 1438–1442 (2005). [CrossRef]

15. A. Chagraoui, A. Tairi, K. Ajebli, H. Bensaid, and A. Moussaoui, “New tellurite glasses and crystalline phases in the Bi₂O₃–CaO–TeO₂ system: Synthesis and characterization,” J. Alloys Compd. 495(1), 67–71 (2010). [CrossRef]

16. G. Zhao, Y. Tian, H. Fan, J. Zhang, and L. Hu, “Properties and Structures of Bi₂O₃–B₂O₃–TeO₂ Glass,” J. Mater. Sci. Technol. 29(3), 209–214 (2013). [CrossRef]

17. A. K. Yadav and P. Singh, “A review of the structures of oxide glasses by Raman spectroscopy,” RSC Advances 5(83), 67583–67609 (2015). [CrossRef]

18. H. Fan, G. Gao, G. Wang, and L. Hu, “Infrared, Raman and XPS spectroscopic studies of Bi₂O₃–B₂O₃–GeO₂ glasses,” Solid State Sci. 12(4), 541–545 (2010). [CrossRef]

19. B. L. Shivachev, T. Petrov, H. Yoneda, R. Titorenkova, and B. Mihailova, “Synthesis and nonlinear optical properties of TeO₂–Bi₂O₃–GeO₂ glasses,” Scr. Mater. 61(5), 493–496 (2009). [CrossRef]

20. V. Dimitrov and S. Sakka, “Electronic oxide polarizability and optical basicity of simple oxides. I,” J. Appl. Phys. 79(3), 1736–1740 (1996). [CrossRef]

21. B. R. Judd, “Optical absorption intensities of rare-earth ions,” Phys. Rev. 127(3), 750–761 (1962). [CrossRef]

22. G. Ofelt, “Intensities of crystal spectra of rare-earth ions,” J. Chem. Phys. 37(3), 511–520 (1962). [CrossRef]

23. G. Zhao, P.-W. Kuan, H. Fan, and L. Hu, “Enhanced green and red upconversion and 2.7μm emission from Er³⁺/Tm³⁺ co-doped bismuth germanate glass,” Opt. Mater. 35(5), 910–914 (2013). [CrossRef]

24. H. Ebendorff-Heidepriem, D. Ehrt, M. Bettinelli, and A. Speghini, “Effect of glass composition on Judd–Ofelt parameters and radiative decay rates of Er³⁺ in fluoride phosphate and phosphate glasses,” J. Non-Cryst. Solids 240(1–3), 66–78 (1998). [CrossRef]

25. T. Izumitani, H. Toratani, and H. Kuroda, “Radiative and nonradiative properties of neodimium doped silicate and phosphate glasses,” J. Non-Cryst. Solids 47(1), 87–99 (1982). [CrossRef]

26. S. Tanabe, T. Ohyagi, N. Soga, and T. Hanada, “Compositional dependence of Judd-Ofelt parameters of Er³⁺ ions in alkali-metal borate glasses,” Phys. Rev. B Condens. Matter 46(6), 3305–3310 (1992). [CrossRef] [PubMed]

27. S. Tanabe, T. Hanada, T. Ohyagi, and N. Soga, “Correlation between ¹⁵¹Eu Mössbauer isomer shift and Judd-Ofelt Ω ₆ parameters of Nd³⁺ ions in phosphate and silicate laser glasses,” Phys. Rev. B Condens. Matter 48(14), 10591–10594 (1993). [CrossRef] [PubMed]

28. H. Takebe, Y. Nageno, and K. Morinaga, “Effect of network modifier on spontaneous emission probabilities of Er³⁺ in oxide glasses,” J. Am. Ceram. Soc. 77(8), 2132–2136 (1994). [CrossRef]

29. F. Huang, X. Li, X. Liu, J. Zhang, L. Hu, and D. Chen, “Sensitizing effect of Ho³⁺ on the Er³⁺: 2.7 μm-emission in fluoride glass,” Opt. Mater. 36(5), 921–925 (2014). [CrossRef]

30. T. Schweizer, D. W. Hewak, B. N. Samson, and D. N. Payne, “Spectroscopic data of the 1.8-, 2.9-, and 4.3-microm transitions in dysprosium-doped gallium lanthanum sulfide glass,” Opt. Lett. 21(19), 1594–1596 (1996). [CrossRef] [PubMed]

31. G. Tang, X. Wen, Q. Qian, T. Zhu, W. Liu, M. Sun, X. Chen, and Z. Yang, “Efficient 2.0 μm emission in Er³⁺/Ho³⁺ co-doped barium gallo-germanate glasses under different excitations for mid-infrared laser,” J. Alloys Compd. 664, 19–24 (2016). [CrossRef]

32. G. Chai, G. Dong, J. Qiu, Q. Zhang, and Z. Yang, “Phase transformation and intense 2.7 μm emission from Er³⁺ doped YF₃/YOF μm -crystals,” Sci. Rep. 3, 1598 (2013). [CrossRef] [PubMed]

33. R. Chen, Y. Tian, B. Li, F. Wang, X. Jing, J. Zhang, and S. Xu, “2 μm fluorescence of Ho³⁺:⁵I₇ → ⁵I₈ transition sensitized by Er³⁺ in tellurite germanate glasses,” Opt. Mater. 49, 116–122 (2015). [CrossRef]

34. D. L. Dexter, “A Theory of Sensitized Luminescence in Solids,” J. Chem. Phys. 21(5), 836–850 (1953). [CrossRef]

35. T. Förster, “Zwischenmolekulare energiewanderung und fluoreszenz,” Ann. Phys. 437(1–2), 55–75 (1948). [CrossRef]

36. Y. Fang, G. Zhao, J. Xu, N. Zhang, Z. Ma, and L. Hu, “Energy transfer and 1.8μm emission in Yb³⁺/Tm³⁺ co-doped bismuth germanate glass,” Ceram. Int. 40(4), 6037–6043 (2014). [CrossRef]

37. L. Tarelho, L. Gomes, and I. Ranieri, “Determination of microscopic parameters for nonresonant energy-transfer processes in rare-earth-doped crystals,” Phys. Rev. B 56(22), 14344–14351 (1997). [CrossRef]

38. D. F. de Sousa and L. A. O. Nunes, “Microscopic and macroscopic parameters of energy transfer betweenTm³⁺ ions in fluoroindogallate glasses,” Phys. Rev. B 66(2), 024207 (2002). [CrossRef]

Transition		⁴I_13/2 → ⁴I_15/2	⁴I_11/2 → ⁴I_15/2	⁴I_11/2 → ⁴I₁ ₃ _/2	Ω₂; Ω₄; Ω₆ ( × 10⁻²⁰cm²) δ ( × 10⁻⁶)
TWLE	Arad (s-1)	269.31	239.18	56.04	6.13;1.99;1.02 0.13
	β (%)	100	81	19
	τ_R (ms)	3.71	3.39
TWLEH	A_rad (s⁻¹)	387.12	420.21	74.89	7.68;1.83;1.20 0.01
	β (%)	100	85	15
	τ_R (ms)	2.58	2.02
BGNE	A_rad (s⁻¹)	456.78	498.53	86.79	9.01;3.06;1.43 0.2
	β (%)	100	85	15
	τ_R (ms)	2.19	1.71
BGNEH	A_rad (s⁻¹)	486.12	605.23	93.13	15.35;3.61;1.45 0.15
	β (%)	100	87	13
	τ_R (ms)	2.06	1.43

Energy transfer	N(# of phonons) (% phonon-assist)	C_DA ( × 10⁻⁴⁰cm⁶/s)	N(# of phonons) (% phonon-assist)	C_AD ( × 10⁻⁴⁰cm⁶/s)
TZL:
ET3:Er³⁺:⁴I_11/2 → Ho³⁺:⁵I₆	1, 2 (5, 95)	0.62	1, 2 (1, 99)	0.11
ET4:Er³⁺:⁴I_13/2 → Ho³⁺:⁵I₇	1, 2 (12, 88)	11.89	1, 2 (1, 99)	4.88
BGN:
ET3:Er³⁺:⁴I_11/2 → Ho³⁺:⁵I₆	3, 4, 5 (50, 48, 2)	0.29	3, 4, 5 (18, 81, 1)	0.04
ET4:Er³⁺:⁴I_13/2 → Ho³⁺:⁵I₇	3, 4, 5 (73, 26, 1)	8.08	3, 4, 5 (37, 60, 3)	2.05

Transition		⁴I_13/2 → ⁴I_15/2	⁴I_11/2 → ⁴I_15/2	⁴I_11/2 → ⁴I₁ ₃ _/2	Ω₂; Ω₄; Ω₆ ( × 10⁻²⁰cm²) δ ( × 10⁻⁶)
TWLE	Arad (s-1)	269.31	239.18	56.04	6.13;1.99;1.02 0.13
	β (%)	100	81	19
	τ_R (ms)	3.71	3.39
TWLEH	A_rad (s⁻¹)	387.12	420.21	74.89	7.68;1.83;1.20 0.01
	β (%)	100	85	15
	τ_R (ms)	2.58	2.02
BGNE	A_rad (s⁻¹)	456.78	498.53	86.79	9.01;3.06;1.43 0.2
	β (%)	100	85	15
	τ_R (ms)	2.19	1.71
BGNEH	A_rad (s⁻¹)	486.12	605.23	93.13	15.35;3.61;1.45 0.15
	β (%)	100	87	13
	τ_R (ms)	2.06	1.43

Energy transfer	N(# of phonons) (% phonon-assist)	C_DA ( × 10⁻⁴⁰cm⁶/s)	N(# of phonons) (% phonon-assist)	C_AD ( × 10⁻⁴⁰cm⁶/s)
TZL:
ET3:Er³⁺:⁴I_11/2 → Ho³⁺:⁵I₆	1, 2 (5, 95)	0.62	1, 2 (1, 99)	0.11
ET4:Er³⁺:⁴I_13/2 → Ho³⁺:⁵I₇	1, 2 (12, 88)	11.89	1, 2 (1, 99)	4.88
BGN:
ET3:Er³⁺:⁴I_11/2 → Ho³⁺:⁵I₆	3, 4, 5 (50, 48, 2)	0.29	3, 4, 5 (18, 81, 1)	0.04
ET4:Er³⁺:⁴I_13/2 → Ho³⁺:⁵I₇	3, 4, 5 (73, 26, 1)	8.08	3, 4, 5 (37, 60, 3)	2.05

Comparative study of 2.7 μm emission of Ho³⁺ desensitized Er³⁺ in tellurite and bismuth glass

Abstract

1. Introduction

2. Experimental

3. Results and discussion

3.1 Raman spectra

3.2 Absorption spectra and Judd–Ofelt analysis

3.3 Photoluminescence spectra and energy transfer process

4. Conclusions

Funding

References and links

Cited By

Figures (6)

Tables (2)

Equations (7)

Optical Materials Express