YNbO_4∶Tm^(3+)/Yb^(3+)上转换发光特性研究

Up-conversion Luminescent Properties of YNbO_4∶ Tm^(3+)/Yb^(3+)

按照50Nb_2O_5-(46-x)Y_2O_3-4Yb_2O_3-x Tm_2O_3(x=0.1,0.2,0.5,1,2)的配比方式,采用高温固相法制备出了掺杂Tm^(3+)/Yb^(3+)的YNb O_4晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm^(3+)离子的~1G_4→~3H_6、~1G_4→~3F_4、~3F_3→~3H_6能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ω_t(t=2,4,6),进而得出理论振子强度及实验振子强度,二者均方根偏差δ_(rms)=1.299×10^(-7)。计算了Tm^(3+)离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论:(1)~3F_4能级寿命较长,适合作为上转换中间能级;(2)~3H_5能级寿命较长,且~3H_5→~3H_6跃迁分支比(96.46%)接近100%,可用于产生1 216 nm激光。

Tm 3+/Yb 3+droped YNbO 4 power sample was prepared with the molar ratios of 50Nb 2O 5-(46-x)Y 2O 3-4Yb 2O 3-x Tm 2O 3(x=0.1,0.2,0.5,1,2)by the high temperature solid state method at 1 300℃.Under 980 nm laser excitation,the upconversion luminescence spectra of samples show 478 nm from 1G 4→3H 6 transition of Tm 3+ions,645 nm attributed to 1G 4→3F 4 transition of Tm 3+ions,respectively,and 707 nm emissions assigned to 3F 3→3H 6 transition of Tm 3+ions.The transition process is estimated by using the relation between the upconversion power and the operating current of the 980 nm laser.The numbers of photons absorbed are 2.72,2.69 and 2.01.The first two correspond to three-photon absorption processes,and the last one corresponds to two-photon absorption process.The spectral properties of the samples are studied by using Judd-Ofelt theory.Spectral strength parametersΩt(t=2,4,6)were computed based on the absorption peak s area of the absorption spectrum.The theoretical oscillator strength and the experimental oscillator strength were calculated according to the spectrum strength parameters,and the root mean square deviation(δrms)was 1.299×10-7.The transition probability,branching ratio and other parameters of the lower level transition of Tm 3+ion were calculated.The results show that:(1)the 3F 4 has a longer level lifetime,which is suitable for up-conversion intermediate level;(2)3H 5 has a longer level lifetime,and the transition branching ratio of 3H 5→3H 6 is close to 100%(96.46%),so this sample can be used to generate 1 216 nm laser.