Abstract: To increase the output power and slope efficiency of up conversion ultraviolet(UV) laser based on the 4f5d state of rare-earth ions doped in hosts, upconversion UV amplifiers can be structured to amplify the output power of oscillators. The laser kinetics for the upconversion UV fiber amplifier based on the transition from 4f5d to the ³H₄ gr ound state in Pr³⁺∶ZBLAN fiber was investigated by using steady population rate equations and propagation equations. The saturation signal power, output power, slope efficiency and optimum fiber length were calculated. There exists a saturated power of input signal. The laser output power is almost independent of the input signal power when the signal power exceeds the saturated value. When the input power is greater than 1 mW, both the output power and the slope efficiency of the amplifier are 2 to 3 times those of the oscillator under the same conditions. The conclusion is that the fiber amplifier can greatly enhance the output power and the slope efficiency of 4f5d upco nversion Pr³⁺∶ZBLAN fiber laser.

Key words: fiber amplifier, Pr³⁺∶ZBLAN, 4f5d state, ultraviolet laser, upconversion