Continuum Surelite EX 10, Operation And Maintenance Manual

Page: 103 / 114

Appendix A: PIV Operation and Maintenance
Crystal phase matching
Phase matching the doubling crystal is occasionally necessary to maintain maximum
energy of the doubled pulses. A toggle switch, mounted on the side of the laser bench,
controls a motor which rotates the crystal while the PIV cover remains closed. To
phase match the crystal do the following:
1. Turn on both lasers and allow them to warm up at least 20 minutes, then raise
their 1,064 nm beam blocks to disengage them.
2. Set a power meter in the PIV output and open the PIV beam dump.
3. Move the SHG toggle switch back and forth to find the crystal position yielding
maximum power. Remember that as the crystal rotates, beam power goes
through many minor maxima, but the central maximum has significantly more
power.
Beam power balance
PIV requires that the pulse from each laser have the same energy. The best way to
balance the energies is to adjust the time interval between the flashlamp firing and
opening the Q-switch, using external control pulses. Adjusting flashlamp voltage
produces a similar result.
Flashlamp voltage
The simplest way to change the YAG beam energy is to adjust the flashlamp discharge
voltage on the YAG power supply. Refer to your Surelite or Powerlite manual for
details. This method has the disadvantage of causing the beam to diverge, its pulse
width to increase, and its harmonic conversion efficiency to decrease.
External control
External control of both flashlamp and Q-switch firing allows control over pulse
energy in the same way. Both the RS232 interface and Direct Access Triggering (DAT
Mode 2) allow this control. Pages
37 to 43 of a Surelite manual give details.
To balance the pulse power from both lasers, do the following:
1. Turn on both Surelites and allow them to warm up.
2. Place a power meter in the PIV output beam and push the shutter button to
close the intracavity shutter of one laser. Then measure the power of the other
laser.
3. Reverse the shutter positions of both lasers and adjust the energy of the second
laser to match the first. Do this either by adjusting the flashlamp discharge
voltage and/or the timing between the fire and Q-switch pulses.