Abstract：YLiF4 codoped with Er3+，Tm3+and Yb3+ ions was synthesized by hydrothermal method. The absorption spectra and upconversion spectra excited at 980 nm were investigated. Under the excitation of infrared photons，strong white emission can be obtained. According to the value of n obtained from the power law，the 484 nm blue emission，524 and 552 nm green emission, and 665 nm red emission are all due to two photon process，while the UV emission is attributed to three photon process. The authors also analyzed the upconversion mechanism and process.
Key words：Upconversion;Hydrothermal;Er3+;Tm3+;Yb3+;Host material YLiF4
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