不同波长激发下YLiF_4∶Er^(3+),Tm^(3+),Yb^(3+)的发光

Emission of YLiF_4 ∶Er^(3+),Tm^(3+),Yb^(3+) Excited with Different Wavelength

水热法合成了YL iF4∶Er3+,Tm3+,Yb3+,其中Er3+、Yb3+和Tm3+的摩尔分数分别为1%、1.5%和2%。当用355 nm光激发时,其发光为蓝色,峰值位于450 nm,对应于Tm3+的1D2→3F4跃迁。用378 nm激发时,发光为绿色,主要发光峰位于552 nm。980 nm光激发时,发光为白色,发光峰分别位于665(651),552(543),484,450 nm处,并在648 nm处还观察到了一个发光峰,其中最强的发射为红光。YL iF4∶Er3+,Tm3+,Yb3+的蓝光来源于Tm3+的激发态1G4到基态3H6的跃迁,绿光来源于Er3+的4S3/2和2H11/2到基态4I15/2的跃迁,红光既来源于Tm3+的1G4→3F4的跃迁,也来源于Er3+的4F9/2→4I15/2的跃迁。在上转换发光中,还探测到了紫外光359 nm的发射。监测665 nm得到的激发光谱不同于监测552 nm的激发光谱,在665 nm的激发光谱中出现了对应Tm3+的1G4能级的峰。在双对数曲线中,蓝光484 nm、绿光552 nm和红光665 nm的斜率分别为2.25、2.28和2.21,紫外光359 nm的斜率为2.85。因此在980 nm激发下,蓝光484 nm、绿光552 nm和红光665 nm都是双光子过程,紫外光359 nm的发射是三光子过程。

The sample of YLiF4：Er^3＋,Tm^3＋,Yb^3＋ is synthesized by hydrothermal method. The mol fraction of Er3^＋, Yb3^＋ and Tm3^＋ is 1%, 1.5 % and 2%, respectively. The emission of YLiF4： Er3^＋ , Tm3^＋ , Yb3^＋ excited by 355 nm is blue light with the peak in 450 nm which comes from the transition of 1^D2→,3^F4 of Tm^3＋. After excited by 378 nm, YLiF4： Er^3＋ , Tm^3＋ , Yb^3＋ emits green light with the main peak in 552 nm. The color of upconversion luminescence of YLiF4：Er^3＋,Tm^3＋,Yb^3＋ excited by 980 nm is white color. The upconversion spectrum exhibits distinct emission peaks at 665 （651）, 552（543 ）, 484 and 450 nm. There is another peak around in 648 nm. The strongest is the light with the wavelength of 665 nm （651 nm）. The blue light comes from the transition of 1^G4→,3^H6 and 1^D2→,3^F4 of Tm^3＋. The green light results from the transition of 4^S3/2 （2^H11/2）→,4^Ⅰ15/2 of Er^3＋. It is proved that the red light originates from the transition 1^G4Ⅰ,3^F4 of Tm^3＋ and the transition of 4^F9/2→,4^Ⅰ15/2 of Er^3＋. The excitation spectrum monitored by 665 nm is different to that monitored by 552 nm. There is an excitation peak corresponding to the energy level 1^G4 of Tm3^＋ in the excitation spectrum of 665 nm. But there is no corresponding peak in the excitation spectrum of 552 nm. It is concluded that there is energy transfer processes between Er3^＋ and Tm3^＋ ions. In the double-log coordinate system, the slope of the emission of 484, 552 and 665 nm is 2.25, 2.28 and 2.21, respectively. The slope of the emission of 359 nm is 2.85. According to this power law, The emission of 484,552 and 665 nm are all due to two photon process, while the emission of 359 nm is due to three photon process.