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Spectroscopic characteristics of Dy3+-doped Y3Al5O12 (YAG) and Y3ScAl4O12 (YSAG) garnet single crystals grown by the micro-pulling-down method
Journal of Luminescence 215 (2019) 116675
Contents lists available at ScienceDirect
Journal of Luminescence journal homepage: www.elsevier.com/locate/jlumin
Spectroscopic characteristics of Dy3+-doped Y3Al5O12 (YAG) and Y3ScAl4O12 (YSAG) garnet single crystals grown by the micro-pulling-down method
T
Jie Xua, Qingsong Songa, Jian Liua, Shidong Zhoua, Yuxin Pana, Dongzhen Lia, Peng Liua, Xiaodong Xua,*, Yuchong Dingb, Jun Xuc,**, Kheirreddine Lebboud a
Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, 221116, China Research & Development Center of Material and Equipment, China Electronics Technology Group Corporation No.26 Research Institute, Chongqing, 400060, China School of Physics Science and Engineering, Institute for Advanced Study, Tongji University, Shanghai, 200092, China d Institut Lumière Matière, UMR5306 Université Lyon1-CNRS, Université de Lyon, Lyon, 69622, Villeurbanne Cedex, France b c
A R T I C LE I N FO
A B S T R A C T
Keywords: Dy:YAG Dy:Y3ScAl4O12 Micro-pulling-down method Spectral property
Dy3+-doped Y3Al5O12 (YAG) and Y3ScAl4O12 (YSAG) single crystals have been successfully grown by the micropulling-down (μ-PD) technique for the first time. The room temperature absorption spectra, fluorescence spectra and fluorescence decay curves were measured. Dy:YAG and Dy:Y3ScAl4O12 crystals exhibit strongest emission centered at 583 nm, corresponding to the 4F9/2 → 6H13/2 transition. The decay lifetime of the 4F9/2 level was measured to be 634 μs and 667 μs, respectively. All these results indicate that the Dy:YAG and Dy:Y3ScAl4O12 crystals are promising candidates for yellow laser operation.
1. Introduction In recently years, lasers sources emitting in the yellow region are very useful in many applications, such as medical treatment, telecommunication, visual display, remote sensing and data storage [1–3]. A new attractive candidate for yellow laser is the trivalent dysprosium ion (Dy3+) due to its 4F9/2 → 6H13/2 transition, which is just suitable for pumping with commercially available InGaN diode lasers. In 2012, Bowman et al. reported an InGaN diode pumped Dy:YAG yellow laser for the first time [4]. Up to now, a great deal of Dy3+ doped host materials have been developed, such as YAG [5], YAlO3 [6], CaYAlO4 [7], CaGdAlO4 [8], NaLa(WO4)2 [9], ZnWO4 [10], GdVO4 [11], Lu2Si2O7 [12], Lu2O3 [13], GdScO3 [14], KY3F10 [15], LiYF4 [16], Dy,Tb:LuLiF4 [17]and so on. Rare earth ions doped YAG single crystals have been realized as important materials for laser applications thanks to their high thermal conductivity, good chemical and mechanical characteristics [18]. Yttrium scandium aluminum (Y3ScxAl5-xO12) crystals doped with rare earth ions are promising laser active materials because of their disordered natures, which leads to inhomogeneous broadening of absorption and emission spectra, with expectations of obtaining efficient Q-switched and mode-locked laser pulse operations [19–22]. The
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growth, spectral properties and laser performance of Dy:YAG crystals have been reported [4,23–26]. However, to the best of our knowledge the growth and spectral properties of Dy:Y3ScxAl5-xO12 crystals have never been reported. In this work, Dy3+-doped YAG and Y3ScAl4O12 crystals were grown by the micro-pulling-down (μ-PD) technique for the first time. Room temperature spectroscopic properties of two crystals were discussed in detail. 2. Experimental 2.1. Crystal growth and structure The Dy3+-doped YAG and Y3ScAl4O12 single crystals were grown by the μ-PD method [27,28]. The 99.999% grade Dy2O3, Sc2O3, Y2O3 and Al2O3 raw materials were weighed according to the formula (Dy0.03Y0.97)3Al5O12, (Dy0.03Y0.97)3Sc1Al4O12, respectively. After the compounds were ground and mixed, they were shaped into a rod and pressed by cold isostatic at 160 MPa for 2 min, then sintered in air at 1300 °C for 20 h. The growth was performed from an iridium crucible with constant pulling rate of 0.30 mm/min by pulling down a < 111 > oriented YAG seed and high-purity flowing argon was used
Corresponding author. Corresponding author. E-mail addresses: [email protected] (X. Xu), [email protected] (J. Xu).
**
https://doi.org/10.1016/j.jlumin.2019.116675 Received 29 April 2019; Received in revised form 5 July 2019; Accepted 26 July 2019 Available online 06 August 2019 0022-2313/ © 2019 Published by Elsevier B.V.
Journal of Luminescence 215 (2019) 116675
J. Xu, et al.
Fig. 1. Photograph of the as-grown Dy:YAG (a) and Dy:Y3ScAl4O12 (b) single crystals.
the measurements were carried out at room temperature.
to prevent oxidation of the crucible. The as grown Dy:YAG and Dy:Y3ScAl4O12 with diameter of about 2 mm are in Fig. 1. The crystals are transparent, and free from cracks and inclusions with homogeneous diameter. A small section of samples was taken from the as-grown single crystals and ground into powders, and the powders were detected in the 2Theta range of 20°–90° by X-ray diffraction method (XRD, Bruker-D2, Germany). Fig. 2 shows the XRD patterns of the Dy3+-doped YAG and Y3ScAl4O12 crystals. All diffraction peaks are well indexed to the standard card of YAG (PDF＃88–2048) and there are no additional impurity peaks in the patterns, indicating that the crystalline structure does not change when doped with Dy3+ and Sc3+ ions. The lattice constants of Dy:YAG and Dy:Y3ScAl4O12 crystals were calculated to be a = 1.1989, and 1.2003 nm, respectively.
3. Results and discussion 3.1. Absorption spectra The absorption spectra of Dy3+-doped YAG and Y3ScAl4O12 single crystals in the range from 300 to 2000 nm at room temperature are shown in Fig. 3. It's clear that absorption bands centered around 326 nm, 353 nm, 367 nm, 386 nm, 427 nm, 448 nm, 479 nm, 752 nm, 802 nm, 905 nm, 1074 nm, 1292 nm and 1687 nm are corresponding to transitions from the 6H15/2 ground state to, 6P7/2, 6P5/2, 4I13/2, 4G11/2, 4 I15/2, 4F9/2, 4F3/2, 6F5/2, 6F7/2, 6F9/2 + 6H7/2, 6F11/2 + 6H9/2 and 6H11/ 2 excited states, respectively. The shape of these absorption bands suggests quite performance of the grown crystals. The absorption bands around 448 nm match well with the emission of commercial InGaN laser diodes. The absorption coefficient at 448 nm of Dy:YAG and Dy:Y3ScAl4O12 was calculated to be 0.38 and 0.40 cm−1. In order to achieve absorption, this requires crystal lengths in the order of centimeters. Using micro-pulling-down method, it is easy to grow crystals with the length of few tens of centimeters, which reduces complexity of obtaining performed laser samples. The full width at half maximum (FWHM) of absorption band at 448 nm was calculated to be 2.3 and 2.5 nm for Dy:YAG and Dy:Y3ScAl4O12, respectively, which is comparable of that of Dy:YAG (1.9 nm) [26] reported previously for a bulk material grown by the Czochralski method but much smaller than that of Dy:GdVO4 (9 nm) [2], Dy:CaGdAlO4 (4.3 nm) [8], and Dy:GdScO3 (9 nm) [14].
2.2. Spectroscopic measurement The samples were cut from the as-grown crystals and two surfaces perpendicular to the < 111 > -growth axis were polished for spectral measurements. The spectral measurements were detected in the core (diameter of 0.5 mm) of the samples. The room temperature absorption spectra of Dy:YAG and Dy:Y3ScAl4O12 crystals were recorded with a UV–VIS–NIR spectrophotometer (Lambda 900, Perkin -Elmer UV-VISNIR) in the range of 300–2000 nm. The fluorescence spectra, as well as the decay curves at 583 nm, were recorded using Edinburgh Instruments FLS980 spectrophotometer under 447 nm excitation. All
Fig. 2. Room temperature XRD patterns of the Dy:YAG and Dy:Y3ScAl4O12 crystals with a standard pattern of YAG (PDF＃88–2048).
Fig. 3. Absorption spectra of Dy:YAG and Dy:Y3ScAl4O12 crystals. 2
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lifetime of Dy:YAG and Dy:Y3ScAl4O12 crystals was measured to be 634 and 667 μs, respectively, which is longer than that of Dy:YAlO3 (185 μs) [6], Dy:LuLiF4 (582 μs) [15], and Dy:CaYAlO4 (425 μs) [7]. All the results show that Dy:YAG and Dy:Y3ScAl4O12 crystals are promising for yellow laser operation. 4. Conclusion For the first time, Dy3+-doped Y3Al5O12 and Y3ScAl4O12 single crystals were successfully grown by the μ-PD technique. The X-ray diffraction patterns show the Dy3+ and Sc3+ ions dopant didn't change the crystalline structure. The absorption spectra, emission spectra and the fluorescence decay curves were measured and analyzed at room temperature. The FWHM of the absorption band at 448 nm was 2.3 nm and 2.5 nm for Dy:YAG and Dy:Y3ScAl4O12, respectively, which matches well with the emission of InGaN laser diodes. The FWHM of the emission band at 583 nm was calculated to be 12.2 and 15.6 nm for Dy:YAG and Dy:Y3ScAl4O12, respectively. The fluorescence lifetime of Dy:YAG and Dy:Y3ScAl4O12 crystals was measured to be 634 and 667 μs, respectively. All results indicate that Dy:YAG and Dy:Y3ScAl4O12 crystals are potential candidates for yellow laser operation.
Fig. 4. Emission spectra of Dy:YAG and Dy:Y3ScAl4O12 crystals.
Acknowledgements This work is partially supported by National Key Research and Development Program of China (No. 2016YFB0701002) and National Natural Science Foundation of China (No. 61621001). References [1] F. Peng, W.P. Liu, Q.L. Zhang, J.Q. Luo, D.L. Sun, G.H. Sun, D.M. Zhang, X.F. Wang, Growth, structure, and spectroscopic characteristics of a promising yellow laser crystal Dy:GdScO3, J. Lumin. 201 (2018) 176–181. [2] C. Krankel, D. Marzahl, F. Moglia, G. Huber, P.W. Metz, Out of the blue: semiconductor laser pumped visible rare-earth doped lasers, Laser Photonics Rev. 10 (2016) 548–568. [3] E. Cavalli, E. Bovero, A. Belletti, Optical spectroscopy of CaMoO4:Dy3+ single crystals, J. Phys. Condens. Matter 14 (2002) 5221–5228. [4] S.R. Bowman, S. O'Connor, N.J. Condon, Diode pumped yellow dysprosium lasers, Opt. Express 20 (2012) 12906–12911. [5] M. Klimczak, M. Malinowski, J. Sarnecki, R. Piramidowicz, Luminescence properties in the visible of Dy:YAG/YAG planar waveguides, J. Lumin. 129 (2009) 1869–1873. [6] B. Liu, J. Shi, Q. Wang, H. Tang, J. Liu, H. Zhao, D. Li, J. Liu, X. Xu, Z. Wang, J. Xu, Crystal growth and yellow emission of Dy:YAlO3, Opt. Mater. 72 (2017) 208–213. [7] H. Chen, P. Loiseau, G. Aka, Optical properties of Dy3+-doped CaYAlO4, crystal, J. Lumin. 199 (2018) 509–515. [8] X. Xu, Z. Hu, R. Li, D. Li, J. Di, L. Su, Q. Yang, Q. Sai, H. Tang, Q. Wang, A. Strze, J. Xu, Optical spectroscopy of Dy3+-doped CaGdAlO4, single crystal for potential use in solid-state yellow lasers, Opt. Mater. 66 (2017) 469–473. [9] Y. Wei, C. Tu, H. Wang, F. Yang, G. Jia, Z. u You, X. Lu, J. Li, Z. Zhu, Y. Wang, Optical spectroscopy of NaLa(WO4)2:Dy3+ single crystal, J. Alloy. Comp. 438 (2007) 310–316. [10] Z. Xia, F. Yang, L. Qiao, F. Yan, End pumped yellow laser performance of Dy3+:ZnWO4, Opt. Commun. 387 (2017) 357–360. [11] M. Higuchi, R. Sasaki, J. Takahashi, Float zone growth of Dy:GdVO4 single crystals for potential use in solid-state yellow lasers, J. Cryst. Growth 311 (2009) 4549–4552. [12] J. Huang, Y. Chen, J. Huang, X. Gong, Y. Lin, Z. Luo, Y. Huang, Spectroscopic investigation of Dy3+:Lu2Si2O7 single crystal: a potential 589 nm laser medium, Opt. Mater. 72 (2017) 156–160. [13] J. Shi, B. Liu, Q. Wang, H. Tang, F. Wu, D. Li, H. Zhao, Z. Wang, W. Deng, X. Xu, J. Xu, Crystal growth, spectroscopic characteristics, and Judd-Ofelt analysis of Dy:Lu2O3 for yellow laser, Chin. Phys. B 27 (2018) 077802. [14] F. Peng, W. Liu, J. Luo, D. Sun, Y. Chen, H. Zhang, S. Ding, Q. Zhang, Study of growth, defects and thermal and spectroscopic properties of Dy:GdScO3 and Dy,Tb:GdScO3 as promising 578 nm laser crystals, CrystEngComm 20 (2018) 6291–6299. [15] S. Bigotta, M. Tonelli, E. Cavalli, A. Belletti, Optical spectra of Dy3+ in KY3F10 and LiLuF4 crystalline fibers, J. Lumin. 130 (2010) 13–17. [16] M.G. Brik, T. Ishii, A.M. Tkachuk, S.E. Ivanova, I.K. Razumova, Calculations of the transitions intensities in the optical spectra of Dy3+:LiYF4, J. Alloy. Comp. 374 (2004) 63–68. [17] G. Bolognesi, D. Parisi, D. Calonico, G.A. Costanzo, F. Levi, P.W. Metz, C. Krankel, G. Huber, M. Tonelli, Yellow laser performance of Dy3+ in co-doped Dy,Tb:LiLuF4,
Fig. 5. Fluorescence decay curves of 4F9/2 level of Dy:YAG and Dy:Y3ScAl4O12 crystals.
3.2. Fluorescence spectra The room temperature emission spectra of Dy:YAG and Dy:Y3ScAl4O12 crystals in the wavelength range of 450–800 nm under excitation at 447 nm are presented in Fig. 4. The emission transitions of Dy3+ ions show sharp emission bands because of the inner shell transitions from the excited state to the lower states. The stronger emission transition bands occur in the blue centered at 483 nm and yellow centered at 583 nm regions, corresponding to the transitions of Dy3+ from 4F9/2 to 6H15/2 and 6H13/2, respectively, whereas the weaker emission transition peaks are located at 676 and 762 nm, which are related to the transitions of Dy3+ from 4F9/2 to 6H11/2 and 6H9/2 + 6F11/ 2, respectively. All measured observed bands reveal well-resolved Stark level structure. The full width at half maximum (FWHM) of emission band at 583 nm was calculated to be 12.2 and 15.6 nm for Dy:YAG and Dy:Y3ScAl4O12, respectively, which is useful for tunable laser and/or ultrashort laser output. It can be clearly observed that the fluorescence bandwidth of Dy:Y3ScAl4O12 is significantly broader than that of Dy:YAG due to the disordered crystalline structure in Dy:Y3ScAl4O12. The fluorescence decay curve of the 4F9/2 level excited by 447 nm at room temperature was presented in Fig. 5. All measured decay curves exhibit a single exponential decaying behavior. The fluorescence 3
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Phys. Rev. 184 (1969) 285–293. [24] U.V. Valiev, J.B. Gruber, Sh A. Rakhimov, V. Yu, Sokolov, Magnetic circular polarization of luminescence of dysprosium–yttrium aluminum garnet Dy0.2Y2.8Al5O12, Opt Spectrosc. 96 (2004) 549–555. [25] S.R. Bowman, N.J. Condon, S.O. Connor, A. Rosenberg, Diode-pumped dysprosium laser materials, Proc. SPIE 7325 (2009) 732507. [26] Y. Pan, S. Zhou, D. Li, B. Liu, Q. Song, J. Liu, P. Liu, Y. Ding, X. Wang, X. Xu, J. Xu, Growth and optical properties of Dy:Y3Al5O12 crystal, Phys. B Condens. Matter 530 (2018) 317–321. [27] J. Wang, Q. Song, Y. Sun, Y. Zhao, W. Zhou, D.Z. Li, X. Xu, C. Shen, W. Yao, L. Wang, J. Xu, D. Shen, High-performance Ho:YAG single-crystal fiber laser inband pumped by a Tm-doped all-fiber laser, Opt. Lett. 44 (2019) 455–459. [28] N. Li, Y. Xue, D. Wang, B. Liu, C. Guo, Q. Song, X. Xu, J. Liu, D. Li, J. Xu, Z. Xu, J. Xu, Optical properties of Nd:Bi4Ge3O12 crystals grown by the micro-pulling-down method, J. Lumin. 206 (2019) 412–416.
Opt. Lett. 39 (2014) 6628–6631. [18] X. Xu, Z. Zhao, P. Song, G. Zhou, J. Xu, P. Deng, Structural, thermal and luminescent properties of Yb-doped Y3Al5O12 crystals, J. Opt. Soc. Am. B 21 (2004) 543–547. [19] T.H. Allik, C.A. Morrison, J.B. Cruber, M.R. Kokta, Crystallography, spectroscopic analysis, and lasing properties of Nd3+:Y3Sc2Al3O12, Phys. Rev. B 41 (1990) 21–30. [20] F. Cornacchia, R. Simura, A. Toncelli, M. Tonelli, A. Yoshikawa, T. Fukuda, Spectroscopic properties of Y3Sc2Al3O12 (YSAG) single crystals grown by μ-PD technique, Opt. Mater. 30 (2007) 135–138. [21] C. Feng, H. Zhang, Q. Wang, J. Fang, Dual-wavelength synchronously mode-locked laser of a Nd:Y3ScAl4O12 disordered crystal, Laser Phys. Lett. 14 (2017) 045804. [22] G.B. Lutts, A.L. Denisov, E.V. Zharikov, A.I. Zagumennyi, S.N. Kozlikin, S.V. Lavrishchev, S.A. Samoylova, GSAG and YSAG: a study on isomorphism and crystal growth, Opt. Quant. Electron. 22 (1990) S269–S281. [23] P. Grunberg, S. Hufner, E. Orlich, J. Schmitt, Crystal field in dysprosium garnets,
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Contents lists available at ScienceDirect
Journal of Luminescence journal homepage: www.elsevier.com/locate/jlumin
Spectroscopic characteristics of Dy3+-doped Y3Al5O12 (YAG) and Y3ScAl4O12 (YSAG) garnet single crystals grown by the micro-pulling-down method
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Jie Xua, Qingsong Songa, Jian Liua, Shidong Zhoua, Yuxin Pana, Dongzhen Lia, Peng Liua, Xiaodong Xua,*, Yuchong Dingb, Jun Xuc,**, Kheirreddine Lebboud a
Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, 221116, China Research & Development Center of Material and Equipment, China Electronics Technology Group Corporation No.26 Research Institute, Chongqing, 400060, China School of Physics Science and Engineering, Institute for Advanced Study, Tongji University, Shanghai, 200092, China d Institut Lumière Matière, UMR5306 Université Lyon1-CNRS, Université de Lyon, Lyon, 69622, Villeurbanne Cedex, France b c
A R T I C LE I N FO
A B S T R A C T
Keywords: Dy:YAG Dy:Y3ScAl4O12 Micro-pulling-down method Spectral property
Dy3+-doped Y3Al5O12 (YAG) and Y3ScAl4O12 (YSAG) single crystals have been successfully grown by the micropulling-down (μ-PD) technique for the first time. The room temperature absorption spectra, fluorescence spectra and fluorescence decay curves were measured. Dy:YAG and Dy:Y3ScAl4O12 crystals exhibit strongest emission centered at 583 nm, corresponding to the 4F9/2 → 6H13/2 transition. The decay lifetime of the 4F9/2 level was measured to be 634 μs and 667 μs, respectively. All these results indicate that the Dy:YAG and Dy:Y3ScAl4O12 crystals are promising candidates for yellow laser operation.
1. Introduction In recently years, lasers sources emitting in the yellow region are very useful in many applications, such as medical treatment, telecommunication, visual display, remote sensing and data storage [1–3]. A new attractive candidate for yellow laser is the trivalent dysprosium ion (Dy3+) due to its 4F9/2 → 6H13/2 transition, which is just suitable for pumping with commercially available InGaN diode lasers. In 2012, Bowman et al. reported an InGaN diode pumped Dy:YAG yellow laser for the first time [4]. Up to now, a great deal of Dy3+ doped host materials have been developed, such as YAG [5], YAlO3 [6], CaYAlO4 [7], CaGdAlO4 [8], NaLa(WO4)2 [9], ZnWO4 [10], GdVO4 [11], Lu2Si2O7 [12], Lu2O3 [13], GdScO3 [14], KY3F10 [15], LiYF4 [16], Dy,Tb:LuLiF4 [17]and so on. Rare earth ions doped YAG single crystals have been realized as important materials for laser applications thanks to their high thermal conductivity, good chemical and mechanical characteristics [18]. Yttrium scandium aluminum (Y3ScxAl5-xO12) crystals doped with rare earth ions are promising laser active materials because of their disordered natures, which leads to inhomogeneous broadening of absorption and emission spectra, with expectations of obtaining efficient Q-switched and mode-locked laser pulse operations [19–22]. The
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growth, spectral properties and laser performance of Dy:YAG crystals have been reported [4,23–26]. However, to the best of our knowledge the growth and spectral properties of Dy:Y3ScxAl5-xO12 crystals have never been reported. In this work, Dy3+-doped YAG and Y3ScAl4O12 crystals were grown by the micro-pulling-down (μ-PD) technique for the first time. Room temperature spectroscopic properties of two crystals were discussed in detail. 2. Experimental 2.1. Crystal growth and structure The Dy3+-doped YAG and Y3ScAl4O12 single crystals were grown by the μ-PD method [27,28]. The 99.999% grade Dy2O3, Sc2O3, Y2O3 and Al2O3 raw materials were weighed according to the formula (Dy0.03Y0.97)3Al5O12, (Dy0.03Y0.97)3Sc1Al4O12, respectively. After the compounds were ground and mixed, they were shaped into a rod and pressed by cold isostatic at 160 MPa for 2 min, then sintered in air at 1300 °C for 20 h. The growth was performed from an iridium crucible with constant pulling rate of 0.30 mm/min by pulling down a < 111 > oriented YAG seed and high-purity flowing argon was used
Corresponding author. Corresponding author. E-mail addresses: [email protected] (X. Xu), [email protected] (J. Xu).
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https://doi.org/10.1016/j.jlumin.2019.116675 Received 29 April 2019; Received in revised form 5 July 2019; Accepted 26 July 2019 Available online 06 August 2019 0022-2313/ © 2019 Published by Elsevier B.V.
Journal of Luminescence 215 (2019) 116675
J. Xu, et al.
Fig. 1. Photograph of the as-grown Dy:YAG (a) and Dy:Y3ScAl4O12 (b) single crystals.
the measurements were carried out at room temperature.
to prevent oxidation of the crucible. The as grown Dy:YAG and Dy:Y3ScAl4O12 with diameter of about 2 mm are in Fig. 1. The crystals are transparent, and free from cracks and inclusions with homogeneous diameter. A small section of samples was taken from the as-grown single crystals and ground into powders, and the powders were detected in the 2Theta range of 20°–90° by X-ray diffraction method (XRD, Bruker-D2, Germany). Fig. 2 shows the XRD patterns of the Dy3+-doped YAG and Y3ScAl4O12 crystals. All diffraction peaks are well indexed to the standard card of YAG (PDF＃88–2048) and there are no additional impurity peaks in the patterns, indicating that the crystalline structure does not change when doped with Dy3+ and Sc3+ ions. The lattice constants of Dy:YAG and Dy:Y3ScAl4O12 crystals were calculated to be a = 1.1989, and 1.2003 nm, respectively.
3. Results and discussion 3.1. Absorption spectra The absorption spectra of Dy3+-doped YAG and Y3ScAl4O12 single crystals in the range from 300 to 2000 nm at room temperature are shown in Fig. 3. It's clear that absorption bands centered around 326 nm, 353 nm, 367 nm, 386 nm, 427 nm, 448 nm, 479 nm, 752 nm, 802 nm, 905 nm, 1074 nm, 1292 nm and 1687 nm are corresponding to transitions from the 6H15/2 ground state to, 6P7/2, 6P5/2, 4I13/2, 4G11/2, 4 I15/2, 4F9/2, 4F3/2, 6F5/2, 6F7/2, 6F9/2 + 6H7/2, 6F11/2 + 6H9/2 and 6H11/ 2 excited states, respectively. The shape of these absorption bands suggests quite performance of the grown crystals. The absorption bands around 448 nm match well with the emission of commercial InGaN laser diodes. The absorption coefficient at 448 nm of Dy:YAG and Dy:Y3ScAl4O12 was calculated to be 0.38 and 0.40 cm−1. In order to achieve absorption, this requires crystal lengths in the order of centimeters. Using micro-pulling-down method, it is easy to grow crystals with the length of few tens of centimeters, which reduces complexity of obtaining performed laser samples. The full width at half maximum (FWHM) of absorption band at 448 nm was calculated to be 2.3 and 2.5 nm for Dy:YAG and Dy:Y3ScAl4O12, respectively, which is comparable of that of Dy:YAG (1.9 nm) [26] reported previously for a bulk material grown by the Czochralski method but much smaller than that of Dy:GdVO4 (9 nm) [2], Dy:CaGdAlO4 (4.3 nm) [8], and Dy:GdScO3 (9 nm) [14].
2.2. Spectroscopic measurement The samples were cut from the as-grown crystals and two surfaces perpendicular to the < 111 > -growth axis were polished for spectral measurements. The spectral measurements were detected in the core (diameter of 0.5 mm) of the samples. The room temperature absorption spectra of Dy:YAG and Dy:Y3ScAl4O12 crystals were recorded with a UV–VIS–NIR spectrophotometer (Lambda 900, Perkin -Elmer UV-VISNIR) in the range of 300–2000 nm. The fluorescence spectra, as well as the decay curves at 583 nm, were recorded using Edinburgh Instruments FLS980 spectrophotometer under 447 nm excitation. All
Fig. 2. Room temperature XRD patterns of the Dy:YAG and Dy:Y3ScAl4O12 crystals with a standard pattern of YAG (PDF＃88–2048).
Fig. 3. Absorption spectra of Dy:YAG and Dy:Y3ScAl4O12 crystals. 2
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lifetime of Dy:YAG and Dy:Y3ScAl4O12 crystals was measured to be 634 and 667 μs, respectively, which is longer than that of Dy:YAlO3 (185 μs) [6], Dy:LuLiF4 (582 μs) [15], and Dy:CaYAlO4 (425 μs) [7]. All the results show that Dy:YAG and Dy:Y3ScAl4O12 crystals are promising for yellow laser operation. 4. Conclusion For the first time, Dy3+-doped Y3Al5O12 and Y3ScAl4O12 single crystals were successfully grown by the μ-PD technique. The X-ray diffraction patterns show the Dy3+ and Sc3+ ions dopant didn't change the crystalline structure. The absorption spectra, emission spectra and the fluorescence decay curves were measured and analyzed at room temperature. The FWHM of the absorption band at 448 nm was 2.3 nm and 2.5 nm for Dy:YAG and Dy:Y3ScAl4O12, respectively, which matches well with the emission of InGaN laser diodes. The FWHM of the emission band at 583 nm was calculated to be 12.2 and 15.6 nm for Dy:YAG and Dy:Y3ScAl4O12, respectively. The fluorescence lifetime of Dy:YAG and Dy:Y3ScAl4O12 crystals was measured to be 634 and 667 μs, respectively. All results indicate that Dy:YAG and Dy:Y3ScAl4O12 crystals are potential candidates for yellow laser operation.
Fig. 4. Emission spectra of Dy:YAG and Dy:Y3ScAl4O12 crystals.
Acknowledgements This work is partially supported by National Key Research and Development Program of China (No. 2016YFB0701002) and National Natural Science Foundation of China (No. 61621001). References [1] F. Peng, W.P. Liu, Q.L. Zhang, J.Q. Luo, D.L. Sun, G.H. Sun, D.M. Zhang, X.F. Wang, Growth, structure, and spectroscopic characteristics of a promising yellow laser crystal Dy:GdScO3, J. Lumin. 201 (2018) 176–181. [2] C. Krankel, D. Marzahl, F. Moglia, G. Huber, P.W. Metz, Out of the blue: semiconductor laser pumped visible rare-earth doped lasers, Laser Photonics Rev. 10 (2016) 548–568. [3] E. Cavalli, E. Bovero, A. Belletti, Optical spectroscopy of CaMoO4:Dy3+ single crystals, J. Phys. Condens. Matter 14 (2002) 5221–5228. [4] S.R. Bowman, S. O'Connor, N.J. Condon, Diode pumped yellow dysprosium lasers, Opt. Express 20 (2012) 12906–12911. [5] M. Klimczak, M. Malinowski, J. Sarnecki, R. Piramidowicz, Luminescence properties in the visible of Dy:YAG/YAG planar waveguides, J. Lumin. 129 (2009) 1869–1873. [6] B. Liu, J. Shi, Q. Wang, H. Tang, J. Liu, H. Zhao, D. Li, J. Liu, X. Xu, Z. Wang, J. Xu, Crystal growth and yellow emission of Dy:YAlO3, Opt. Mater. 72 (2017) 208–213. [7] H. Chen, P. Loiseau, G. Aka, Optical properties of Dy3+-doped CaYAlO4, crystal, J. Lumin. 199 (2018) 509–515. [8] X. Xu, Z. Hu, R. Li, D. Li, J. Di, L. Su, Q. Yang, Q. Sai, H. Tang, Q. Wang, A. Strze, J. Xu, Optical spectroscopy of Dy3+-doped CaGdAlO4, single crystal for potential use in solid-state yellow lasers, Opt. Mater. 66 (2017) 469–473. [9] Y. Wei, C. Tu, H. Wang, F. Yang, G. Jia, Z. u You, X. Lu, J. Li, Z. Zhu, Y. Wang, Optical spectroscopy of NaLa(WO4)2:Dy3+ single crystal, J. Alloy. Comp. 438 (2007) 310–316. [10] Z. Xia, F. Yang, L. Qiao, F. Yan, End pumped yellow laser performance of Dy3+:ZnWO4, Opt. Commun. 387 (2017) 357–360. [11] M. Higuchi, R. Sasaki, J. Takahashi, Float zone growth of Dy:GdVO4 single crystals for potential use in solid-state yellow lasers, J. Cryst. Growth 311 (2009) 4549–4552. [12] J. Huang, Y. Chen, J. Huang, X. Gong, Y. Lin, Z. Luo, Y. Huang, Spectroscopic investigation of Dy3+:Lu2Si2O7 single crystal: a potential 589 nm laser medium, Opt. Mater. 72 (2017) 156–160. [13] J. Shi, B. Liu, Q. Wang, H. Tang, F. Wu, D. Li, H. Zhao, Z. Wang, W. Deng, X. Xu, J. Xu, Crystal growth, spectroscopic characteristics, and Judd-Ofelt analysis of Dy:Lu2O3 for yellow laser, Chin. Phys. B 27 (2018) 077802. [14] F. Peng, W. Liu, J. Luo, D. Sun, Y. Chen, H. Zhang, S. Ding, Q. Zhang, Study of growth, defects and thermal and spectroscopic properties of Dy:GdScO3 and Dy,Tb:GdScO3 as promising 578 nm laser crystals, CrystEngComm 20 (2018) 6291–6299. [15] S. Bigotta, M. Tonelli, E. Cavalli, A. Belletti, Optical spectra of Dy3+ in KY3F10 and LiLuF4 crystalline fibers, J. Lumin. 130 (2010) 13–17. [16] M.G. Brik, T. Ishii, A.M. Tkachuk, S.E. Ivanova, I.K. Razumova, Calculations of the transitions intensities in the optical spectra of Dy3+:LiYF4, J. Alloy. Comp. 374 (2004) 63–68. [17] G. Bolognesi, D. Parisi, D. Calonico, G.A. Costanzo, F. Levi, P.W. Metz, C. Krankel, G. Huber, M. Tonelli, Yellow laser performance of Dy3+ in co-doped Dy,Tb:LiLuF4,
Fig. 5. Fluorescence decay curves of 4F9/2 level of Dy:YAG and Dy:Y3ScAl4O12 crystals.
3.2. Fluorescence spectra The room temperature emission spectra of Dy:YAG and Dy:Y3ScAl4O12 crystals in the wavelength range of 450–800 nm under excitation at 447 nm are presented in Fig. 4. The emission transitions of Dy3+ ions show sharp emission bands because of the inner shell transitions from the excited state to the lower states. The stronger emission transition bands occur in the blue centered at 483 nm and yellow centered at 583 nm regions, corresponding to the transitions of Dy3+ from 4F9/2 to 6H15/2 and 6H13/2, respectively, whereas the weaker emission transition peaks are located at 676 and 762 nm, which are related to the transitions of Dy3+ from 4F9/2 to 6H11/2 and 6H9/2 + 6F11/ 2, respectively. All measured observed bands reveal well-resolved Stark level structure. The full width at half maximum (FWHM) of emission band at 583 nm was calculated to be 12.2 and 15.6 nm for Dy:YAG and Dy:Y3ScAl4O12, respectively, which is useful for tunable laser and/or ultrashort laser output. It can be clearly observed that the fluorescence bandwidth of Dy:Y3ScAl4O12 is significantly broader than that of Dy:YAG due to the disordered crystalline structure in Dy:Y3ScAl4O12. The fluorescence decay curve of the 4F9/2 level excited by 447 nm at room temperature was presented in Fig. 5. All measured decay curves exhibit a single exponential decaying behavior. The fluorescence 3
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