Study On Time Domain Characteristics Of Quasi Continuous Fiber Laser

Quasi continuous fiber laser is widely used in high-end drilling,welding and cleaning fields.The time-domain characteristics of laser pulse directly affect the performance of fiber laser and the quality of laser processing.Therefore,the research on the stability of laser pulse is very important,but the research on this problem is relatively less.In this paper,a high-power quasi continuous fiber laser is built,and the methods to improve the stability of laser pulse are studied from two aspects of current and laser.It is found that the driving current and laser pulse of the laser produce overshoot and relaxation oscillation.Based on the simulation results,the reason of this phenomenon is analyzed and verified by experiments.By prolonging the rise time of the current and increasing the bias current,the stable pulse output is obtained in the high power quasi continuous fiber laser.The main contents of this paper are as follows:A high-power quasi continuous fiber laser is designed and constructed.The laser adopts915 nm double end pump structure.The final optical conversion efficiency reaches 70.8%.The output average power can reach 75 W under the modulation mode of 10 ms pulse width,10 Hz repetition rate and 10% duty cycle.The industrial processing test is carried out by using the laser.According to the constant current theory,a constant current driving power supply based on FET is designed and built.Based on the circuit simulation analysis and experimental results,the time of the rising edge of the voltage and pulse current of the switching power supply is adjusted to solve the overshoot and relaxation oscillation of the rising edge of the output current of the power supply,and the stable pulse current output with smooth waveform is realized.The overshoot phenomenon of the rising edge of the output laser pulse of the quasi continuous fiber laser is studied experimentally.The relationship between the overshoot parameter and the current setting is discussed and the mechanism of the overshoot is analyzed.Based on the cavity rate equation and boundary conditions,the resonator simulation model of the quasi continuous fiber laser is established.Combined with the experimental and simulation results,the overshoot phenomenon of the rising edge of the laser is successfully suppressed by increasing the bias current.