Research on Mid-Infrared Parametric Oscillators - Part 05

3.Experimental Results and Analysis 3.1Output Characteristics of Fiber Pulsed Lasers The laser power after passing through the isolation collimator and the PBS was measured using a power meter (Ophir FL250 A-BB-50), and the results are shown in Figure 4. It can be seen that the output power of the fiber pulsed laser increases linearly with the increase of the power of the second-stage power amplifier (LD). When the power of the second-stage power amplifier (LD) is 115 W, the output power of the laser after passing through the isolation collimator is 84.4 W, corresponding to an optical-to-optical conversion efficiency of 65.1%, and the output power after passing through the PBS is 43.7 W. The output spot was observed using a focus spot analyzer (Ophir LBS-300s), as shown in Figure 4. The temporal and spectral characteristics of the fiber laser pulse at the highest pump power are shown in Figures 5 and 6, respectively. During laser amplification, the pulse width gradually widens, with an output pulse width of 120 ns. When the repetition frequency is 150 kHz, the center wavelength of the output laser is 1064.3 nm, the 3 dB spectral width is 3.47 nm, and the beam quality factor M2 is 1.62. 

Fig. 4 Nanosecond fiber laser power after ISO Collimator versus second stage LD power and beam profile 

Fig. 5 The diagram of nanosecond fiber laser time domain characteristic 

Fig. 6 The diagram of nanosecond fiber laser spectrum