ORPHEUS User’s Manual
30
Light Conversion
6.
DAILY OPERATION
The ORPHEUS device should always be powered on
–
every time it is switched off the motors lose
their position by a few steps. In that case it may be necessary to reset their positions using the WinTOPAS
software, this operation is described in the troubleshooting section. Every time the power to ORPHEUS is
switched off/on, the USB cable may need to be re-connected to the computer.
The pump laser should be turned on by following the guidelines in the user’s manual for the laser.
Typical warm-up time for the system from a cold start should be about 20-30 minutes. It is recommended
to let the system warm up before opening the main shutter of ORPHEUS.
Before operating ORPHEUS, always inspect that the laser is operating at the same parameters as
during installation of the device. Check that you are using the same repetition rate and laser power. Use of
the pulse picker feature to lower the repetition rate is acceptable.
Never operate ORPHEUS with higher
than nominal input pulse energy, when OPA was aligned by trained service engineer. Too high pulse
energy may result in damage to the optical components.
6.1
Setting the Wavelength
1.
Start the WinTOPAS application.
2.
Select the device to be operated (only applicable if more than one OPA/NOPA is controlled by the
same computer).
3.
Type in the wavelength of interest and press Enter.
4.
Place an appropriate wavelength separator at the output of ORPHEUS to separate the Signal and
Idler beams.
5.
Open the shutter by pressing the button in the software.
Please refer to the manual of WinTOPAS for more information on software operation and other ways
to control the output of ORPHEUS.
6.2
Optimizing the Output
To optimize the power,
you should first try to optimize the angle of “SHG crystal” stage while
monitoring the output with a power meter. The angle of this crystal is very sensitive, and second harmonic
generation can be severely diminished even if the stage is off by only a few steps. Tuning is performed via
the “
Motors
”
section in WinTOPAS.
The next motors to check would be “Crystal 2” and “Delay 3”. Changing
the positions of these stages also influences the output wavelength, so it is recommended to check the
output with a spectrometer as well.
If you find it necessary to optimize one motor at every wavelength by a constant number of steps,
you can introduce an offset to the calibration curve. Follow the instructions of paragraph 7.7 in the
troubleshooting section.
If the OPA is producing insufficient parametric output, input beam alignment should be checked. It is
possible to gently push the BRM2 module in various directions while monitoring the output power
–
this
provides a non-destructive way to check if the input beam direction needs optimization. If you see that
doing so increases the output, you can adjust the fine screws of the BRM2 kinematic mount with a 2 mm
hex key to maximize the power.