Growth and Spectral Properties of Er∶CNGG Crystals by the Micro-Pulling-Down Method

doi:10.16553/j.cnki.issn1000-985x.2025.0022

Abstract

Abstract: Er∶CNGG crystals with the doping concentration （atomic fraction） of 0.3%， 2.0%， 3.0% and 5.0% were grown by the micro-pulling-down method. The crystal structure was tested by X-ray diffraction （XRD）， and the results show that the crystal structure is cubic. The absorption spectra， fluorescence spectra and fluorescence decay curves of Er∶CNGG crystals were measured at room temperature. The absorption coefficient of 5.0% Er∶CNGG crystal is 1.70 cm^-1 at 968 nm， with a full width at half maximum （FWHM） of 17.5 nm， which matches well with the commercial laser diode pumping sources. The strongest emission peak of 5.0% Er∶CNGG crystal is located at 2 709 nm with FWHM of 17.3 nm. The lifetime of ⁴I_13/2energy level of 0.3%， 2.0%， 3.0% and 5.0% Er∶CNGG crystals are 5.97， 6.30， 6.46 and 5.73 ms， respectively. The results show that Er∶CNGG crystal is a potential gain medium for laser at around 2.7 μm.

Key words: Er∶CNGG; micro-pulling-down method; crystal growth; spectral property; 2.7 μm; gain medium for laser

CLC Number:

O782

CHEN Zihang, WANG Xiaodan, LIU Jian, LIU Peng, XU Xiaodong, XU Jun. Growth and Spectral Properties of Er∶CNGG Crystals by the Micro-Pulling-Down Method[J]. Journal of Synthetic Crystals, 2025, 54(6): 935-941.

Figures/Tables 9

Fig.1 Photograph of as-grown Er∶CNGG crystals

Fig.2 XRD patterns of Er∶CNGG crystals and standard pattern of CNGG

Table 1 Lattice parameters of CNGG and Er∶CNGG crystals

Crystal	a=b=c/nm	V/nm³
CNGG	1.250 7	1.956 4
0.3% Er∶CNGG	1.250 4	1.954 9
2.0% Er∶CNGG	1.249 6	1.951 3
3.0% Er∶CNGG	1.248 0	1.943 9
5.0% Er∶CNGG	1.246 8	1.938 2

Fig.3 Absorption spectra of Er∶CNGG crystals

Table 2 Absorption coefficient and FWHM at 968 nm of Er∶CNGG crystals

Doping concentration/%	Absorption coefficient at 968 nm/cm^-1	FWHM/nm
0.3	0.09	18.2
2.0	0.45	17.1
3.0	0.96	16.8
5.0	1.70	17.5

Fig.4 Fluorescence spectra of Er∶CNGG crystals

Table 3 FWHM of 4I11/2→4I13/2 transition in Er∶CNGG crystals

Doping concentration/%	FWHM/nm	FWHM/nm	FWHM/nm
0.3	49.7 （2 652 nm）	20.5 （2 709 nm）	58.2 （2 795 nm）
2.0	54.9 （2 653 nm）	19.7 （2 709 nm）	67.3 （2 797 nm）
3.0	43.3 （2 651 nm）	17.6 （2 709 nm）	56.9 （2 797 nm）
5.0	42.1 （2 652 nm）	17.3 （2 709 nm）	54.2 （2 797 nm）

Fig.5 Fluorescence decay curves of 4I11/2 （a） and 4I13/2 （b） energy level of Er∶CNGG crystals

Fig.6 Energy level diagram of Er3+

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