Qioptiq DIV 20 Instruction Manual - page 5
5
4. Operation
This description explains operation of the DIV 20 as driver for the laser
modulator series LM 0202 or LM 13 in the light chopper mode. For these
modulators a special cable and an adapter are included with the DIV 20.
Operation of the DIV 20 with other modulators or in other modes is similar.
The DIV20 has to be switched off for any connecting procedures.
Begin setup (see Appendix A) by connecting the special adapter with the
modulator, such that the banana plugs are fully inserted (step 1). For the
completion of the adapter connection, the two housing screws of the plug have
to be screwed into the modulator housing (step 2). Then connect the special
plug of the cable´s modulator-side to the adapter (step 3) and finally the cable´s
input side (2 triaxial plugs) to the output sockets (Offset) and (Pulse) of the DIV
20 as depicted in Appendix B. Also connect the ground Banana-plug to the
corresponding Banana-plug at the DIV 20.
If you want to use another cable instead of the included special cable, please
note that cable length must be less than 0.5 m with a capacity of less than 40
pF/m. Otherwise reduction of the specifications is possible. The connected
system (including the cable) must have a sufficient isolation strength to
withstand the maximum output voltage. Also EMC-qualities of the new cables
would have to be proven by the applicant to justify a CE-certification.
Connect your TTL-signal generator
with “Input TTL” socket and attach the
Ferrite (delivered with the DIV 20) to the cable used for the connection. For best
EMC-performance also use Ferrites on the modulator-cable (Appendix C).
Switch on the DIV 20 using the power switch (S4): the line control LED
indicates power on.
The DC-Offset knob (PO) controls the offset voltage within the range 0 V to
+600 V. This permits compensating possible double refraction induced
birefringence of the modulator and choosing the optimum working point.
Before setting the offset voltage, the modulator should have reached thermal
equilibrium with the environment. The offset voltage chosen is such that mini-
mum light intensity is achieved behind the modulator. Make sure that the mode
switch (S1) is set to the LOW position. In order to reach optimum conditions,
the modulator must be correctly aligned as well. Please refer to the manual
laser modulator LM 0202.
Finally, by optimizing the setting of offset and pulse voltage, the light intensity
will be minimum in the LOW position of the mode switch (S2) and maximum in
the HIGH position. Further increase of the pulse voltage will only reduce the
maximum light intensity. Once correctly adjusted, the pulse voltage does not
need any further readjustment. Changing temperatures, on the other hand,
might require readjustment of the offset voltage.
Once correct values for pulse and offset voltages are found, set the mode
switch (S2) to the PULSE position. Set the output voltage of your signal
generator such that the DIV 20 is reliably triggered according to +5 V TTL-