An Endurance DPSS laser measuring pulse width, frequency and energy.
Exploring Q-switch Cr:YAG modulation for 10 watt DPSSL Nd:YAG laser.
- Frequency of all pulses.
- Frequencies for main and secondary pulses.
- Energy deviation for 10 consecutive pulses.
- Pulses forms.
- Pulses width.
Fig.1 shows a diagram for measuring the DPSS laser pulse amplitude, frequency and shape.
Fig. 1. Diagram of measuring DPSS laser parameters
The laser beam passes through a half reflection mirror onto a photodetector. The mirror is necessary for attenuation of the laser radiation hitting the photodetector to avoid its damage. The photodetector is based on a reverse-biased photodiode (ФД-225). The photodetector is assembled on an FD-225 photodiode according to a reverse bias scheme. The photodetector output signal goes to the oscilloscope input.
Fig. 2. Pulse period
Fig.2 shows the pulse period. The period is not steady. It varies within a fairy narrow range of 32-36 µs. Consequently, the pulse frequency varied from 28 to 31 kHz.
Fig. 3. Pulse amplitude
The pulse amplitude is not constant too. As is seen in fig. 3, it changes within a rather broad range. The difference between the minimum and maximum low energy is 45%.
Fig. 4 shows a greater number of pulses per unit of time to present more vividly the changes in the pulse amplitude relative to one another.
Fig. 4. Pulse amplitude
The different scanning pulse shape is seen in figs. 5 and 6.
Fig 5. Singel-pulse shape
Fig 6. Single-pulse shape
As seen from figs. 5 and 6, the pulse seems to consist of two pulses, the amplitude of the first one is much greater than that of the other one. But not all the pulses have the same shape. Fig. 7 shows a single pulse without a subsequent one with a smaller amplitude.
Fig. 7. Single-pulse shape