Multicolor Fluorescence And Compound White Laser Of Lanthanide Doped Nanocrystals

Lanthanide ions are endowed with unique upconversion optical properties,which generated great interest in many aspects.For example,upconversion white laser is one of the research hotspots.However,Lanthanide ions doping has a low upconversion efficiency.Now,high upconversion efficiency is mostly realized by using Lanthanide ions doped core-shell-shell nanocrystals.But this structure nanocrystals were synthesized by the multi-step method with low yield.In this paper,upconversion nanoparticles were synthesized by the hydrothermal method.The samples of red,green and blue colors were synthesized respectively to obtain high efficiency.Three samples are physically mixed,and then the intensity ratio of red,green and blue is changed by adjusting the mass ratio samples.Finally,the random cavity gain effect of the powder sample is used to obtain the white light laser emission.In this thesis,Yb³⁺/Er³⁺,Yb³⁺/Tm³⁺doped in La F₃ matrix by hydrothermal method.The single particle size is less than 50 nm.The influence of the type and concentration of Ln³⁺on the crystal phase of the sample was studied.It is confirmed that heavy levels of Yb³⁺in La F₃ will destroy the crystal phase of the matrix.The effect of Ln³⁺doping on the luminescence characteristics of upconversion nanoparticles was studied.The mechanism of mixing three samples in different proportions on the color was explored.The results show that the red sample La F₃:70%Yb³⁺-2%Er³⁺,the green sample La F₃:10%Yb³⁺-2%Er³⁺and the blue sample La F₃:10%Yb³⁺-1%Tm³⁺have high upconversion efficiency.Under the continuous wave laser pumping of 980 nm,the tunable color can be realized by changing the ratio of three samples.When the mass ratio of red,green and blue samples is 4:1:4,their color coordinate is(0.3313,0.3413),which can achieve high-quality upconversion white light output.This paper also discusses the laser behavior of red,green and blue light in a random gain cavity.Under the excitation of nanosecond pulsed laser source with an output wavelength of 980 nm,the random laser emission of red,green,blue and upconversion white were observed and confirmed.These results indicate that upconversion white laser can be realized by adjusting the mass ratio of red,green and blue samples prepared by a simple process.It provides a new method for the application of upconversion materials in the field of full-color display and backlight.