ORPHEUS User’s Manual
Light Conversion support@lightcon.com 31
7. OPTIMIZATION OF ORPHEUS PERFORMANCE
7.1 Checking Pump Laser Parameters
The output performance of ORPHEUS is very sensitive to the input beam/pulse parameters. If the
output from ORPHEUS changes significantly – the parameters of the pump laser would be the first thing to
check.
The most important pump laser characteristics are the following:
1. Pump pulse energy.
2. Pump beam profile, diameter and collimation.
3. Pump pulse duration and compression.
4. Wavelength and spectral width.
5. Contrast ratio (pre- and post- pulses).
6. Stability of output parameters (pulse-to-pulse).
Pump pulse energy is supposed to be kept the same or at least ±10-15% from the energy that was
used during the installation. If the pump pulse energy will be significantly lower – there might be no output
from ORPHEUS or the output might be significantly lower, instable. If pulse energy is high – there is a risk of
damaging optical components of ORPHEUS and the crystals. Pulse energy might change because of the
following:
• Different pump current of laser diodes in laser.
• Changes of internal repetition rate of laser.
• Clipping of the beam on beam steering optics, damage of beam steering optics.
• Additional pump beam splitting or attenuation before ORPHEUS, etc.
• Degradation of the elements of amplifier or misalignment of cavity (lower output).
Pump pulse energy can be calculated from total power of pump laser and repetition rate. Please
check the installation documentation for pump pulse energy for ORPHEUS.
The profile of the beam should be at least visually inspected from time to time. Hot spots in the
beam profile, diffraction patterns because of clipping might create small scale non-linear effects or even
damage of the optical components inside ORPHEUS. The change of the diameter and/or collimation will
change the focusing conditions of the beams inside leading to lower/no output from the system.
Different pulse duration and compression affect the output of ORPHEUS similar as different pulse
energy. The compression/duration however does not change the energy of the pulse, but it changes the
peak intensity. Usual indicator of problems with pulse duration is white light generator of ORPHEUS: if
pulse duration is instable or higher than usual – WLC intensity will also be instable or it may even not be
possible to obtain white light generation. This appears in most of the cases because of CW presence in the
output from oscillator. Different pulse duration can originate from:
• Misalignment of compressor length – can be checked/adjusted from the remote control.
• CW spectral modulation of oscillator output – can be monitored with a spectrometer.
• Nanosecond operation if oscillator is off / not mode-locked / in CW regime / seed is blocked.
• Misalignment of stretcher / amplifier / compressor.
• Different wavelength and spectral width from the oscillator.
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