Enhanced 2.7 &#x003BC;m mid-infrared emissions of Er3&#x0002B; via Pr3&#x0002B; deactivation and Yb3&#x0002B; sensitization in LiNbO3 crystal

Peixiong Zhang; Zhenqiang Chen; Yin Hang; Zhen Li; Hao Yin; Siqi Zhu; Shenhe Fu; Anming Li

doi:10.1364/OE.24.025202

1. Introduction

Over the past several decades, mid-IR (MIR) lasers operating around 2.7–3 μm have received extensive attention for numerous applications in medicine, remote sensing, military countermeasures, and atmosphere pollution monitoring due to the strong water absorption and short penetration depths of a few micrometers into biological tissue around this spectral region [1–5]. In addition, 2.7–3 μm lasers can be used as efficient and high-quality pump sources for longer wavelength mid-IR lasers and optical parametric oscillators [6–8].

Erbium ion is an ideal luminescent center for 2.7 μm emission with the transition of ⁴I_11/2 → ⁴I_13/2, and Er³⁺ doped garnets [9–12] and fluorides [13] crystalline materials have been widely studied and demonstrated as 2.7 μm laser sources. However, the 2.7 μm laser operation cannot be obtained efficiently due to (i) the absorption coefficient of Er³⁺ ion around 970 nm is significantly low, limiting the pump efficiency, and (ii) the self-terminating “bottleneck” effect, which may result from the fluorescence lifetime of the upper ⁴I_11/2 level is considerably shorter than that of the lower level ⁴I_13/2 [14]. In order to conquer these problems, on one hand, because the strong overlap of the luminescence spectrum of Yb³⁺ ions and the absorption spectrum of acceptor Er³⁺ ions, Yb³⁺ has can be as an efficient sensitizer ion to transfer the accumulated excitation energy to the Er³⁺ ions to improve the absorption efficiencies with commercially available 970 nm pumping sources [15–17]. On the other hand, high doping concentrations (>30 at. %) of Er³⁺ can mitigate the self-termination bottleneck by well known concentration dependent up-conversion process [⁴I_13/2+⁴I_13/2 → ⁴I_11/2+⁴I_9/2]. However, high doping concentration of Er³⁺ may give rise to a decline in the quality of crystal, limiting the laser output efficiency and beam quality. Another method of mitigating the self-termination bottleneck is the co-doping of deactivation ion, which can efficiently quench the lower level ⁴I_13/2 of Er³⁺, leading to population inversion. Up to now, with the codoped of deactivation ion (such as Pr³⁺, Ho³⁺, Tm³⁺, etc.), efficient “quenchers” of luminescence from the level ⁴I_13/2 have been achieved in luminescent materials [18–20]. We are now focusing our scientific program on Pr³⁺ ion, because its energy level ⁴F₄ is adjacent to level ⁴I_13/2 of Er³⁺. Predictably, it is believed that co-doping of both Yb³⁺ and Pr³⁺ with Er³⁺ without heavily doping of Er³⁺ may turn on the possibility of excellent 2.7 μm lasers performance from Er³⁺ under a conventional 970 nm LD pump.

Figure 1 shows the simplified energy level diagram of Er³⁺, Yb³⁺ and Pr³⁺ triply doped system. When the crystal is pumped by a 970 nm laser diode, ions of Yb³⁺: ²F_7/2 state is excited to Yb³⁺:²F_5/2. Then transferring the energy to the Er³⁺: ⁴I_11/2 level thanks to the effective resonance energy transfer from Yb³⁺ to Er³⁺. Then, on one hand, some Er³⁺ ions in ⁴I_11/2 level would decay radiatively to the ground state ⁴I_15/2 with 1.0 μm emission, on the other hand, other ions in ⁴I_11/2 level would decay to ⁴I_13/2 with 2.7 μm emission, or nonradiatively to ⁴I_13/2 without emission. Subsequently, ions in the ⁴I_13/2 level would undergo energy transition (ET) process to the ³F₄ level of Pr³⁺, depopulating the Er³⁺: ⁴I_13/2 level, which may induce the population inversion and facilitate laser operation.

Fig. 1 Simplified energy level diagram of Er³⁺, Yb³⁺ and Pr³⁺ triply doped system.

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The well-known versatile LiNbO₃ (LN) crystal has been widely used in optoelectronic devices because of its electro-optic, piezo-electric, and nonlinear optical physical properties [21–23]. LN crystal has been extensively doped with rare-earth ions, in which laser oscillation, electro-optic and nonlinear optics effects can be integrated within just one crystal [24–26]. Er³⁺ doped LN crystal has been widely investigated for it operates at the eye-safe 1.54 μm laser, and the miniaturization of solar cells [27, 28]. However, to our knowledge, the observation of emission around 2.7 μm in Er³⁺, Yb³⁺, and Pr³⁺ triply doped LN crystal has not been successfully obtained. In this letter, Er³⁺, Yb³⁺, and Pr³⁺ triply doped LN crystal (Er/Yb/Pr: LN) was successfully prepared. Yb³⁺ ion was demonstrated to be an effective sensitizer for Er³⁺ ion in Er/Yb/Pr: LN crystal. Pr³⁺ was demonstrated to enhance the Er³⁺: ⁴I_11/2 → ⁴I_13/2 2.7 μm emission in Er/Yb/Pr: LN crystal by depopulating the Er³⁺: ⁴I_13/2 level while having little influence on the Er³⁺: ⁴I_11/2 level. The spectroscopic investigation of 2.7 μm emission has also been made for future applications in MIR lasers.

2. Experimental section

The 0.6 at.% Er³⁺, 1.0 at.% Yb³⁺, and 0.3 at.% Pr³⁺ triply doped and 0.6 at.% Er³⁺, 1.0 at.% Yb³⁺ codoped LN (Er/Yb: LN) crystals were grown by the Czochralski method with intermediate frequency induction heating. Li₂CO₃ (99.999%), Nb₂O₅ (99.999%), Yb₂O₃ (99.999%), Er₂O₃ (99.999%), and Pr₂O₃ (99.999%) were used as raw material for crystal growth. the mixture was pressed into disks and heated in air at 1150 °C for 12 h to remove CO₂ and form polycrystalline powers. Then, the polycrystalline powers were followed loaded into platinum crucible for crystal growth along the ferroelectric c axis. The pulling rate and rotation rate were 0.6–0.8 mm/h, and 8–12 rpm, respectively. Before being cut into wafers for experiment, the crystals were polarized at 1200 °C with a current density of 6–8 mA/cm² to produce a single-domain crystal.

The inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to measure the concentrations of Er³⁺, Yb³⁺, and Pr³⁺ ions in the as grown crystals. The concentrations of Er³⁺ and Yb³⁺ in double doped crystal were 0.75 at.%, and 1.28 at.%, respectively. The corresponding segregator coefficients of Er³⁺ and Yb³⁺ of Er/Yb: LN crystal were 1.25, and 1.28, respectively. The concentrations of Er³⁺, Yb³⁺, and Pr³⁺ in triply doped crystal were 0.73 at.%, 1.26 at.%, and 0.27 at.%, respectively. The corresponding segregator coefficients of Er³⁺, Yb³⁺, and Pr³⁺ were 1.21, 1.26, and 0.91, respectively. It is clear to see that although the concentration of Er³⁺ ions in the melt is constant (0.6 at.%), the concentration of Er³⁺ ions in the crystal decreases (from 0.75 at.% to 0.73 at.%) when the total impurity concentration increases (after the codoped of Pr³⁺ ions), which is consistent with the results of Er³⁺/Yb³⁺ codoped LN crystal published by E. Cantelar et al. [29].

The analysis of Er³⁺, Yb³⁺, and Pr³⁺ ion absorption was carried out by a UV-VIS-NIR spectrophotometer (ModelV-570, JASCO Co.). The fluorescence spectra in range of 2700 nm to 3000 nm and fluorescence decay profiles of the double-doped and triply-doped crystals were acquired by Edinburgh Instruments FLS920 and FSP920 spectrophotometers with a laser diode (LD) as the pump source (excited at 970 nm), and an optical parametric oscillator pulse laser. All measurements were done at room temperature.

In order to reduce an artificial lifetime lengthening due to radiation trapping [30], the following test technologies have been taken: (i) the thickness of crystals for experiment measuring was as thin as 1.0 mm; (ii) the excited laser beam was focused near the edge of crystals; (iii) the measurements were performed by the pin-hole method [31], the crystals were placed behind a pin-hold with a variable aperture from 0.5 mm to 1.5 mm at an angle of 45 °C with respect to the excited laser beam and the axis of the collection optics.

3. Experimental results and discussion

The visible-near-IR absorption spectra of Er/Yb/Pr: LN crystal was shown in Fig. 2. It is clear to see that in the range of 400–2100 nm, there are 10 typical absorption bands of Er³⁺ ion, centered at approximately 380, 406, 454, 492, 524, 548, 658, 804, 978, and 1528 nm, which correspond to the transitions from Er³⁺: ⁴I_15/2 to ⁴G_11/2, ²H_9/2, ⁴F_5/2+⁴F_3/2, ⁴F_7/2, ²H_11/2, ⁴S_3/2, ⁴F_9/2, ⁴I_9/2, ⁴I_11/2, and ⁴I_13/2, respectively.

Fig. 2 Absorption spectrum of Er/Yb/Pr: LN crystal in the range of 400–2100 nm. The inset shows absorption spectrum of Er: LN, Er/Yb: LN, and Er/Yb/Pr: LN crystals in the range of 850–1700 nm.

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On one side, as L. E. Bausa [32] and E. Montoya [33] have pointed out that there is a wide and strong absorption band corresponds to the Yb³⁺ optical transition ²F_7/2→²F_5/2 centered at 970 nm in LN crystal. It is clear to see from the inset of Fig. 2, in the range of 850–1050 nm, there is a strong overlap between the transition of Yb³⁺ ions and Er³⁺ ions. By contrast, the absorption of the crystal without Yb³⁺ ion (Er: LN) is significantly weak. Therefore, Yb³⁺ ion can act as a sensitizer to Er³⁺ ion by nonradiative energy transfer, resulting in an increased absorption efficiency, which is beneficial to effectively enhance the pump efficiency.

On the other side, I. Baumann [34] has reported that in the range of 1310–1700 nm, there is an absorption band due to the transition of Pr³⁺: ³H₄→³F₄ in Ti/Pr: LN waveguide. As the inset of Fig. 2 shows, in the range of 1400–1700 nm, a strong overlap between Er³⁺: ⁴I_15/2 → ⁴I_13/2 transition and Pr³⁺: ³H₄ → ³F₄ transition can be seen. It is expected that efficient energy transfer will occur from the lower ⁴I_13/2 level of Er³⁺ to the ³F₄ states of Pr³⁺ in the Er/Yb/Pr: LN crystal, leading in depopulating the Er³⁺: ⁴I_13/2 level.

L. Nunez et al. [35] have made a systematic study on the polarized optical absorption of Er³⁺ doped LN crystal, and they found that compared with the unpolarized theory, the Judd-Ofelt parameters Ω₄ and Ω₆ were in good agreement, while the Ω₂ was different. Therefore, it is best to apply a fully polarized Judd-Ofelt treatment for optical performance characterization. However, in some cases, it is supposed that a unpolarized absorption spectra approximates to some extent an average of π and σ polarizations and may be used within in the framework of the unpolarized Judd-Ofelt theory [36], and limited to the existing test-bed condition, here we only made a fully unpolarized Judd-Ofelt treatment for optical performance characterization. In order to separate the Pr³⁺ and Yb³⁺ ions absorption peaks, only the following 8 absorption bands centered at approximately 380, 406, 454, 492, 524, 548, 658, and 804 nm, which correspond to the transitions from Er³⁺: ⁴I_15/2 to ⁴G_11/2, ²H_9/2, ⁴F_5/2+⁴F_3/2, ⁴F_7/2, ²H_11/2, ⁴S_3/2, ⁴F_9/2, and ⁴I_9/2, respectively, were used to calculated the intensity parameters Ω_2,4,6 of Er³⁺ based on the Judd-Ofelt theory [37,38]. Moreover, the absorption coefficient for measured concentrations was corrected. The intensity parameters Ω_2,4,6 of Er³⁺ are shown in Table 1. To justify our fitting quality, the root-mean-square (RMS) deviation between the experimental and the calculated line strengths was calculated to be as low as 0.08×10⁻²⁰ cm², which confirms the creditability of calculations and the validity of the J-O theory for predicting the spectral intensities of Er³⁺. It is clear to see that the Ω₂ of Er³⁺ in Er/Yb/Pr: LN crystal is higher than that of Er/Yb: LN crystal. It is well known that the value of Ω₂ drops with the improved symmetry of rare-earth ions site [39]. The larger Ω₂ of Er³⁺ in Er/Yb/Pr: LN crystal indicates that the introduction of Pr³⁺ ions leads to a lower symmetry surrounding Er³⁺ ions. The fluorescence branching ratio (β) and the radiative lifetime (τ_r) were calculated by using the intensity parameters Ω_2,4,6 of Er³⁺ in our crystal and are also shown in Table 1. It is clear to see that the fluorescence branching ratio β of ⁴I_11/2 → ⁴I_13/2 transition for 2.7 μm fluorescence emission in Er/Yb/Pr: LN crystal is as high as 16.32%, which is higher than that (12.21%) of Er/Yb: LN crystal, indicating that the codoping of Pr³⁺ ions makes the Er/Yb: LN crystal more easily induces the 2.7 μm fluorescence emission and facilitates laser operation.

Table 1. Judd-Ofelt parameters Ω_2,4,6, branching ratio β, lifetime of ⁴I_11/2 and ⁴I_13/2 levels for Er³⁺ ions (τ_m and τ_r are the measured and calculated radiative lifetime) of Er/Yb/Pr: LN and Er/Yb: LN crystals.

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In order to understand the energy transfer between Yb³⁺ and Er³⁺ ions, the decay curve of the Yb³⁺:²F_5/2 energy level for the luminescence at 1060 nm of Er/Yb/Pr: LN crystal was measured and shows in Fig. 3. The inset of Fig. 3 shows the Ln of fluorescence intensity I versus time t, which is unable to be linear fitting, indicating that the decay curve can not be fitted to single exponential function. It can be well fitted to dual exponential decaying, and the fitted curve is also shown in Fig. 3. The measured lifetime of the Yb³⁺:²F_5/2 manifold in the Er/Yb/Pr: LN crystal is 320 μs, which is much shorter than that of Er: LN crystal (580 μs) [40]. This reduced lifetime indicates that an additional relaxation channel (energy transfer from Yb³⁺ to Er³⁺) has been activated [41]. The energy transition efficiency from Yb³⁺ to Er³⁺ can be estimated by the following equation: η_ET1=1−τ_{Er/Yb/Pr@1060nm}/τ_Yb@1060nm, where τ_{Er/Yb/Pr@1060nm} and τ_Yb@1060nm are the Yb³⁺ lifetimes of Er/Yb/Pr: LN crystal, and Yb: LN crystal, respectively. The calculated energy transfer efficiency η_ET1 from Yb³⁺ to Er³⁺ is as high as 44.8 %. This confirms that Yb³⁺ ion is a suitable sensitizer in Er/Yb/Pr: LN crystal and can efficiently transfer energy to Er³⁺ ion, making this crystal propitious to be pumped by commercialized InGaAs LD. It is worth mentioning that based on the results of Er³⁺/Yb³⁺ codoped LN crystal published by E. Cantelar [41], the energy transfer efficiency η_ET1 can be further improved by reducing the concentration of Yb³⁺ in Er/Yb/Pr: LN crystal.

Fig. 3 Fluorescence decay curves of the Yb³⁺:²F_5/2 energy level of Er/Yb/Pr: LN crystal. The inset show the Ln of fluorescence intensity I versus time t.

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Figure 4 shows the emission spectra of Er/Yb/Pr: LN and Er/Yb: LN crystals in the range of 1400–1700 nm, and 2500–3000 nm. It can be see that the emission intensity of the Er/Yb/Pr: LN crystal is at least two times that of the Er/Yb: LN crystal at 2.7 μm, whereas emission at 1.5 μm is reverse. This enhanced 2.7 μm emission and reduced 1.5 μm emission in the Er/Yb/Pr: LN crystal is mainly attributed to the quenching effect of the Er³⁺: ⁴I_13/2 by energy transition to Pr³⁺: ³F₄. The emission cross sections are subsequently calculated by the Fuchtbauer-Ladenburg equation [42]:

σ_{em} = \frac{A β λ^{5} I (λ)}{8 π c n^{2} \int λ I (λ) d λ}

where I(λ)/∫ λI(λ)dλ is the normalized line shape function of the experimental emission spectrum, β is the fluorescence branching ratio, c is the speed of light, n is the refractive index, and A is the spontaneous emission probability. It is worth noting that the maximum emission cross section of the crystal codoped with Pr³⁺ is 2.35×10⁻²⁰ cm² at 2745 nm, which is larger than that of the crystal without Pr³⁺ codoping (1.37×10⁻²⁰ cm²). It may be ascribed to the higher fluorescence branching ratio β of ⁴I_11/2 → ⁴I_13/2 transition (from 12.21% to 16.32%), and the shorter radiative lifetime (from 1.48 ms to 1.05 ms) with the codoped of Pr³⁺ ions (shown in Table 1).

Fig. 4 (a) 2.7 μm emission spectrum of Er/Yb/Pr: LN and Er/Yb: LN crystals; (b) 1.5 μm emission spectrum of Er/Yb/Pr: LN and Er/Yb: LN crystals.

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The ability of a deactivation ion (Pr³⁺) receiving energy from a donor (Er³⁺) is an important factor to evaluate the acceptor (Pr³⁺) as a deactivation ion. In order to investigate the energy interaction mechanism between Er³⁺ and Pr³⁺, the time-resolved decays of the Er³⁺: ⁴I_11/2, and ⁴I_13/2 multiplets for the Er/Yb/Pr: LN and Er/Yb: LN crystals were measured, and the results are shown in Fig. 5, and the inset of (a)(b)(c)(d) show the Ln of fluorescence intensity I versus time t. It is clear to see that the curves of the inset of (a)(b)(c)(d) are unable to be linear fitting, indicating that the these four decay curves can not be fitted to single exponential functions. They can be well fitted to dual exponential decaying, and the fitted curves are also shown in Fig. 5.

Fig. 5 (a)(b)Fluorescence decay curves of the Er³⁺:⁴I_11/2 and ⁴I_13/2 energy levels of Er/Yb: LN crystal. (c)(d)Fluorescence decay curves of the Er³⁺:⁴I_11/2 and ⁴I_13/2 multiplets of Er/Yb/Pr: LN crystal. The inset of (a)(b)(c)(d) show the Ln of fluorescence intensity I versus time t.

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On the one hand, the decay curves of the Er³⁺:⁴I_11/2 energy level of Er/Yb: LN and Er/Yb/Pr: LN crystals are shown in Fig. 5(a) and 5(c). And the measured lifetime of Er³⁺: ⁴I_11/2 level in Er/Yb/Pr: LN crystal is 234 μs, which is only 16% shorter than that of Er/Yb: LN crystal (280 μs). This unconspicuous shortening of the measured lifetime indicates that the codoping of Pr³⁺ ions has little influence on the higher laser ⁴I_11/2 level of Er³⁺. On the other hand, the decay curves of the Er³⁺:⁴I_13/2 energy level of Er/Yb: LN and Er/Yb/Pr: LN crystals are shown in Fig. 5(b) and 5(d). The measured lifetime of the lower laser ⁴I_13/2 level in the Er/Yb/Pr: LN crystal is 2.18 ms, which is 42% shorter when compared with the date for the Er/Yb: LN crystal (3.78 ms, which is consistent with the results of Er³⁺ codoped LN crystal published by J. A. Munaoz [30]). This shortening of the measured lifetime confirms that the codoped of Pr³⁺ ions are able to effectively depopulate the Er³⁺: ⁴I_13/2 for 2.7 μm emission in LN crystal by energy transition from Er³⁺: ⁴I_13/2 to Pr³⁺: ³F₄, which may induce the population inversion and facilitate laser operation.

To further investigate the energy interaction mechanism between Er³⁺ and Pr³⁺, the energy transition efficiency can be estimated by the following equation: η_ET =1−τ_Er/Yb/Pr/τ_Er/Yb, where τ_Er/Yb/Pr and τ_Er/Yb are the Er³⁺ lifetimes monitored with and without Pr³⁺ ions, respectively. Therefore, the energy transition efficiency from Er³⁺: ⁴I_11/2 level to Pr³⁺: ¹G₄ level was calculated to be only 0.16. However, the energy transition efficiency from Er³⁺: ⁴I_13/2 level to Pr³⁺: ³F₄ level was calculated to be as high as 0.42. It is demonstrated again that Pr³⁺ can efficiently quench the lower laser level of Er³⁺ by energy transition, which may induce the population inversion and enhance the emission of 2.7 μm.

4. Conclusion

In conclusion, Er/Yb: LN crystals codoped with and without Pr³⁺ ion were successfully grown. Compared with the Er/Yb: LN crystal, the Er/Yb/Pr: LN crystal presents an enhanced 2.7 μm luminescence emission under 970 nm excitation, and an higher fluorescence branching ratio (16.32%) corresponding to the stimulated emission of Er³⁺: ⁴I_11/2 → ⁴I_13/2 transition. It was also demonstrated that the introduced Pr³⁺ depopulates the lower laser level of Er³⁺: ⁴I_13/2, and has little influence on the higher laser level of Er³⁺: ⁴I_11/2 at the same time, which is benefited the possible population inversion for the transition of Er³⁺: ⁴I_11/2 → ⁴I_13/2. Moreover, the energy transition efficiency from Er³⁺: ⁴I_11/2 level to Pr³⁺: ¹G₄ level, and from Er³⁺: ⁴I_13/2 level to Pr³⁺: ³F₄ level were calculated to be 0.16, and 0.42, respectively. The results and analyzed energy transfer indicate codoping of Pr³⁺ with Yb³⁺ in Er:LN crystal plays an important role in 2.7 μm emission when the crystal is pumped by a conventional 970 nm LD.

Funding

National Natural Science Foundation of China (NSFC) (614750671, 1404332, 51302283, 51472257); Guangdong Science and Technology Department (2014B090903014, 2014B010131004, 2014B010124002, 2015B090901014, 2016B090917002).

References and links

1. I. D. Aggarwal, L. B. Shaw, and J. S. Sanghera, “Chalcogenide glass fiber-based mid-IR sources and applications,” Proc. SPIE. 6453, 645312 (2007). [CrossRef]

2. H. Guo, L. Liu, Y. Wang, C. Hou, W. Li, M. Lu, K. Zou, and B. Peng, “Host dependence of spectroscopic properties of Dy³⁺–doped and Dy³⁺, Tm³⁺–codped Ge-Ga-S-CdI₂ chalcohalide glasses,” Opt. Express 17, 15350 (2009). [CrossRef] [PubMed]

3. J. S. Sanghera, L. B. Shaw, and I. D. Aggarwal, “Chalcogenide Glass-Fiber-Based Mid-IR Sources and Applications,” IEEE J. Sel. Top. Quantum Electron. 15, 114 (2009). [CrossRef]

4. M. D. Alessandro, U. W. Niklaus, L. B. Sonia, and M. R. Izilda, “Pulse–Energy–Enhanced, Strongly Modulated Er:YLF Laser for Medical Applications,” AIP Conf. Proc. 992, 415 (2008). [CrossRef]

5. S. D. Jackson and A. Lauto, “Diode-pumped fiber lasers: A new clinical tool?” Laser Surg. Med. 30, 184 (2002). [CrossRef]

6. K. L. Vodopyanov, “Mid-infrared optical parametric generator with extra-wide (3–19 μm) tunability: applications for spectroscopy of two-dimensional electrons in quantum wells,” J. Opt. Soc. Am. B 16(9), 1579–1586 (1999). [CrossRef]

7. K. L. Vodopyanov, F. Ganikhanov, J. P. Maffetone, I. Zwieback, and W. Ruderman, “ZnGeP₂ optical parametric oscillator with 3.8–12.4 μm tunability,” Opt. Lett. 25(11), 841–843 (2000). [CrossRef]

8. B. C. Dickinson, P. S. Golding, M. Pollnau, T. A. King, and S. D. Jackson, “Investigation of a 791 nm pulsed-pumped 2.7 μm Er-doped ZBLAN fibre laser,” Opt. Commun. 191, 315–321 (2001). [CrossRef]

9. E. Arbabzadah, S. Chard, H. Amrania, C. Phillips, and M. Damzen, “Comparison of a diode pumped Er:YSGG and Er:YAG laser in the bounce geometry at the 3 μm transition,” Opt. Express 19(27), 25860–25865 (2011). [CrossRef]

10. J. Chen, D. Sun, J. Luo, H. Zhang, R. Dou, J. Xiao, Q. Zhang, and S. Yin, “Spectroscopic properties and diode end-pumped 2.79 μm laser performance of Er,Pr:GYSGG crystal,” Opt. Express 21(20), 23425–23432 (2013). [CrossRef] [PubMed]

11. D. W. Chen, C. L. Fincher, T. S. Rose, F. L. Vernon, and R. A. Fields, “Diode-pumped 1-W continuous-wave Er:YAG 3 μm laser,” Opt. Lett. 24(6),385–387 (1999). [CrossRef]

12. C. Ziolek, H. Ernst, G. F. Will, H. Lubatschowski, H. Welling, and W. Ertmer, “High-repetition-rate, high-average-power, diode-pumped 2.94 μm Er:YAG laser,” Opt. Lett. 26(9),599–601 (2001). [CrossRef]

13. T. Jensen, A. Diening, G. Huber, and B. H. Chai, “Investigation of diode-pumped 2.8 μm Er:LiYF₄ lasers with various doping levels,” Opt. Lett. 21(8),585–587 (1996). [CrossRef] [PubMed]

14. T. Sandrock, A. Diening, and G. Huber, “Laser emission of erbium-doped fluoride bulk glasses in the spectral range from 2.7 to 2.8 μm,” Opt. Lett. 24, 382 (1999). [CrossRef]

15. J. Silver, M.I. Martinez-Rubio, T.G. Ireland, G.R. Fern, and R. Withnall, “Yttrium Oxide Upconverting Phosphors. Part 2: Temperature Dependent Upconversion Luminescence Properties of Erbium in Yttrium Oxide,” J. Phys. Chem. B 105, 948 (2001). [CrossRef]

16. S. Xu, Z. Yang, J. Zhang, G. Wang, S. Dai, L. Hu, and Z. Jiang, “Upconversion fluorescence spectroscopy of Er³⁺/Yb³⁺-codoped lead oxyfluorosilicate glass,” Chem. Phys. Lett. 385, 263 (2004). [CrossRef]

17. A. S. Oliveira, M. T. de Araujo, A. S. Gouveia-Neto, J. A. Medeiros Neto, A. S. B. Sombra, and Y. Messaddeq, “Frequency upconversion in Er³⁺/Yb³⁺-codoped chalcogenide glass,” Appl. Phys. Lett. 72, 753 (1998). [CrossRef]

18. Z. Zhu, J. Li, Z. You, Y. Wang, S. Lv, E. Ma, J. Xu, H. Wang, and C. Tu, “Beneft of Pr³⁺ ions to the spectral properties of Pr³⁺/Er³⁺: CaGdAlO₄ crystal for a 2.7 μm laser,” Opt. Lett. 37, 4838–4840 (2012). [CrossRef] [PubMed]

19. Y. Choi, K. Kim, B. Lee, Y. Shin, Y. Kim, and J. Heo, “Emission properties of the Er³⁺: ⁴I_11/2 → ⁴I_13/2 transition in Er³⁺- and Er³⁺/Tm³⁺-doped Ge-Ga-As-S glasses,” J. Non-Cryst. Solids 278, 137–144 (2000). [CrossRef]

20. Y. Huang, F. Hu, and L. Zhang, “Er³⁺/Ho³⁺-codoped fuorotellurite glasses for 2.7 μm fber laser materials,” Fibers 1, 11–20 (2013). [CrossRef]

21. R. S. Weis and T. K. Gaylord, “Lithium niobate: Summary of physical properties and crystal structure,” Appl. Phys. A. 37, 191–203 (1985). [CrossRef]

22. X. Li, D. Qu, W. Wang, X. Zhao, L. Zhang, and X. Meng, “Improved nonvolatile holographic storage sensitivity of near-stoichiometric LiNbO₃:Fe:Mn crystals,” Chin. Opt. Lett. 10(12), 122101 (2012). [CrossRef]

23. J. G. Sole, L. Bausa, D. Jaque, E. Montoya, H. Murrieta, and F. Jaque, “Rare earth and transition metal ion centers in LiNbO₃,” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 54, 1571(1998). [CrossRef]

24. R. Zhang, H. Li, P. Zhang, Y. Hang, and J. Xu, “Efficient 1856 nm emission from Tm,Mg:LiNbO₃ laser,” Opt. Express 21, 20990–20998 (2013). [CrossRef] [PubMed]

25. P. Zhang, Y. Hang, J. Gong, C. Zhao, J. Yin, and L. Zhang, “Growth, optical characterization and evaluation of laser properties of Yb³⁺, Mg²⁺:LiTaO₃ crystal,” J. Cryst. Growth. 364, 57–61(2013). [CrossRef]

26. H. Qi, Z. Song, G. Peng, S. Li, and C. Wang, “Short distributed feedback fiber laser with unidirectional output for sensing applications,” Chin. Opt. Lett. 11(4), 041407 (2013). [CrossRef]

27. J. Yang, Y. Tang, and J. Xu, “Development and applications of gain-switched fiber lasers [Invited],” Photon. Res. 1, 52–57(2013). [CrossRef]

28. Y. Liao, J. Xu, Y. Cheng, Z. H. Zhou, F. He, H. Y. Sun, J. Song, X. S. Wang, Z. Z. Xu, K. Sugioka, and K. Midorikawa, “Electro-optic integration of embedded electrodes and waveguides in LiNbO₃ using a femtosecond laser,” Opt. Lett. 33, 2281 (2008). [CrossRef] [PubMed]

29. E. Cantelar, J. A. Sanz-Garcasa, and F. Cusso, “Growth of LiNbO₃ co-doped with Er³⁺/Yb³⁺,” J. Crystal Growth , 205, 196–201 (1999). [CrossRef]

30. J. A. Munoz, B. Herreros, G. Lifante, and F. Cusso, “Concentration Dependence of the 1.5 μmEmission Lifetime of Er³⁺ in LiNbO₃ by Radiation Trapping,” Phys. Stat. Sol. (a) 168, 525–530 (1998). [CrossRef]

31. H. Kuhn, S. T. Fredrich-Thornton, C. Krankel, R. Peters, and K. Petermann, “Model for the calculation of radiation trapping and description of the pinhole method,” Opt. Lett. 32(13),, 1908–1910 (2007). [CrossRef] [PubMed]

32. L. E. Bausa, M.O. Ramirez, and E. Montoya, “Optical performance of Yb³⁺ in LiNbO₃ laser crystal,” Phys. Stat. Sol (a) 201, 289–297 (2004). [CrossRef]

33. E. Montoya, A. Lorenzo, and L. E. Bausa, “Optical characterization of LiNbO₃: Yb³⁺ crystals,” J. Phys. Condens. Matter 11, 311–320 (1999). [CrossRef]

34. I. Baumann, F. Cusso, B. Herreros, H. Holzbrecher, H. Paulus, K. Schafer, and W. Sohler, “Praseodymium-doped Ti:LiNbO₃ waveguides,” Appl. Phys. A 68, 321–324 (1999). [CrossRef]

35. L. Nunez, G. Lifante, and F. Cusso, “Polarization effects on the line-strength calculations of Er³⁺-doped LiNbO₃,” Appl. Phys. B. 62, 485–491 (1996). [CrossRef]

36. T. S. Lomheim and L. G. DeShazer, “Optical-absorption intensities of trivalent neodymium in the uniaxial crystal yttrium orthovanadate,” J. Appl. Phys. 49, 5517 (1978). [CrossRef]

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

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

39. C. K. Jorgensen and R. Reisfeld, “Judd-Ofelt parameters and chemical bonding,” J. Less-Common Met. 93(1), 107–112 (1983). [CrossRef]

40. E. Cantelar and F. Cusso, “Dynamics of the Yb³⁺ to Er³⁺ energy transfer in LiNbO₃,” Appl. Phys. B 69, 29–33 (1999). [CrossRef]

41. E. Cantelar and F. Cusso, “Analytical solution of the transfer rate equations in LiNbO₃:Er³⁺/Yb³⁺,” J. Phys. Condensed Matter 12, 521–527 (2000). [CrossRef]

42. B. F. Aull and H. P. Jenssen, “Vibronic interactions in Nd:YAG resulting in nonreciprocity of absorption and stimulated emission cross sections,” IEEE J. Quantum Electron. 18, 925 (1982). [CrossRef]

Enhanced 2.7 μm mid-infrared emissions of Er³⁺ via Pr³⁺ deactivation and Yb³⁺ sensitization in LiNbO₃ crystal

Abstract

1. Introduction

2. Experimental section

3. Experimental results and discussion

4. Conclusion

Funding

References and links

Cited By

Figures (5)

Tables (1)

Equations (1)

Optics Express

	Ω_2,4,6(10⁻²⁰ cm²)			⁴I_11/2 → ⁴I_13/2	⁴I_11/2		⁴I_13/2

	Ω₂	Ω₄	Ω₆	β(%)	τ_r (ms)	τ_m(ms)	τ_r (ms)	τ_m(ms)
Er/Yb/Pr: LN	8.92	1.51	0.81	16.32	1.05	0.234	3.19	2.18
Er/Yb: LN	8.25	1.21	2.30	12.21	1.48	0.280	4.56	3.78