MOGlabs CEF, Manual

Page: 34 / 60

20
Chapter 4. Troubleshooting
WARNING:
Ensure that the filter is never perpendicular to the laser axis
(filter angle 0
◦
, notch horizontal in fig. 3.1) if the diode is powered on. The
filter is a highly reflective mirror that will back-reflect light into the diode,
which can cause catastrophic damage.
To change the wavelength:
1. Set the laser current so that the output power is sufficient, taking
care to ensure that the internal cavity power is below the maximum
rated for the bare diode i.e. without feedback (see Fig. 2.1).
For adjustments of greater than 1nm:
2. Unlock the filter so that it can rotate, by turning the spindle-clamp
lock screw anti-clockwise, for example one full turn.
3. Rotate the filter assembly spindle using an allen key or hex ball
driver in the hex socket in the centre of the shaft, making sure that
the notch does not align at 0
◦
to the laser body.
4. Lock the spindle-clamp.
For adjustments of less than 1nm:
5. Check that the spring-plunger is engaged but not locked against the
brass arm of the spindle clamp. That is, the pin should be visibly
protruding from the spring-plunger screw, and touching the brass
arm.
6. Adjust the filter angle using the fine thread
λ
adjust screw, acting
against the spring-loaded plunger opposite to the
λ
adjust screw.
7. The laser will hop between external cavity modes as the wavelength
is adjusted, through cycles of dim and bright output.
8. It may be necessary to adjust the spring plunger, so that pressure is
maintained on the brass arm of the spindle clamp, without locking
completely.