采用共沉淀法制备β-NaYF4∶Yb3+, Er3+。X射线衍射图谱结果表明退火有利于β相生长。样品在970 nm处有一强烈吸收峰，利用980 nm激光激发样品，实现红、绿、蓝三色上转换发光；其中蓝光相对较弱，红、绿光的发射峰分别为521，539，659 nm。速率方程表明红、绿发射对应跃迁均是双光子过程，实验结果与理论分析相符。此外，对红、绿发射带面积比的研究表明激发功率和Yb3+掺杂量影响发光颜色；进而可实现简便的色彩设计。

Upconversion luminescence is one of the most efficient progress for the generation of visible radiation by near-infrared (NIR) excitation. A lot of studying works indicated, that, under 980 nm excitation, Yb3+/Er3+ and Yb3+/Tm3+ co-doped NaYF4 materials are well-known because of the highest upconversion efficiency so far. Due to the feature of NIR excitation, frequency upconversion materials would have wide and potential application in light emitting displays, multiplexed biological labeling, short-wavelength lasers and so on. In general, the manipulating color is implemented by changing the intensities of red, green and blue, respectively. The method is complex and expensive. For frequency upconversion red, green and blue lights can be emitted at same time by only one pump NIR laser and the proportions of red/green and red/blue are variable with the pump power. So, the simple color design can be obtained based on the upconversion luminescence. This paper specially discussed a feasible approach to modulate the output color based on the upconversion materials. In this paper the upconversion phosphors NaYF4∶Yb3+, Er3+ were prepared by co-precipitation progress. XRD patterns of the samples showed that the annealing process at 400~600 ℃ induced transformation from the cubic to the hexagonal phase that benefits the upconversion emission. A strong absorption peak near 970 nm was observed, which is due to the transition from ground state 2F2/7 to excited state 2F2/5 of Yb3+. Upconversion luminescence of red, green and blue was obtained under the excitation of 980 nm diode in NaYF4∶Yb3+, Er3+. However, the blue light is too weak to observe. Green and red emissions centered at 521, 539 and 659 nm, correspond to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 of Er3+, respectively. The rate equation was built for this upconversion system. From the rate equations the two photons process is obtained for the green and red luminescence under low pump power. The experimental slope agrees with the results from the rate equations. A liner relationship between the pump power and the equivalent wavelength was obtained. The luminescent color can be continuously modulated in a broad wavelength region by changing the pump power. The equivalent wavelength region is also variable with the dopant concentration of Yb3+. In this work, the range is near 40 nm from 588 nm to 624 nm for 10%Yb3+. When dopant concentration of Yb3+ increases, the wavelength region shifts to blue. This study offers an approach for quantitatively modulating the emission color. This method is simple and easy to operate. It has a potential industrial application in light-emitting displays, anti-counterfeiting techniques， and so on.