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SolsTiS User Manual v10.0
corresponding to roughly one étalon FSR (~0.15-0.7nm), depending on
the model purchased.
2.
To avoid overshoot, it is recommended that the
Etalon Tune
tuning speed
setting is first set to the highest percentage increment by adjusting the
black underscore beneath the tuning percentage, ie. 50.00%. As the
étalon is tuned and the user approaches the required wavelength, the
Etalon Tune
percentage increment can then be reduced from a unit to one
decimal place to two decimal places eg. Starting at 50.00 to 51.00 to
51.20 to 51.23.
3.
As the étalon can be tuned through a wavelength range that is greater
than one étalon FSR, the user may need to tune (either up or down)
through a wavelength jump to the next étalon mode in order to access the
required wavelength. Similarly, if the required wavelength is reached close
to a jump to the next étalon mode, or if the Etalon Tune control is not
roughly centred when the target wavelength is reached, it may be possible
to reach the target wavelength away from a mode jump by tuning the
étalon in reverse through the étalon mode jump. If it is still not possible to
access the required wavelength without tuning the étalon close to a mode
jump, the BRF should be tuned a few steps up or down (i.e., single step
clicks up or down) to try to use the BRF to ‘pull’ or ‘push’ the laser output
wavelength relative to the étalon transmission peak. The étalon tuning
procedure should then be repeated.
Single Longitudinal Mode Operation
– Locking the Intracavity Etalon
to a SolsTiS Cavity Mode (SolsTiS-PX, -PSX, -SRX)
Once SolsTiS has been fine tuned to the required wavelength, the
Etalon
Lock
button on the laser control page of the UI may be pushed. This locks
the peak of the étalon transmission function to the nearest longitudinal
mode frequency that is oscillating in the SolsTiS laser cavity. The indicator
on the left-hand status window will confirm the lock condition.
Note!
I
t is recommended that SolsTiS’ wavelength is
monitored via a high precision wavemeter as the
Etalon
Lock
is applied to see if the output wavelength jumps. Any
wavelength change should ideally be less than one SolsTiS
cavity mode spacing (~0.7GHz). If a wavelength jump on
the order of or greater than one SolsTiS cavity FSR is
observed, this may be a sign of a poor etalon lock (see
below).
1.
If the
Etalon Lock
does not engage after several attempts, the
étalon voltage may be too close to the end of the étalon peak
lock circuit capture range, and therefore may need to be tuned
slightly until locking is achieved. This may be adjusted using the
Etalon Tune
control, and in this case it is advisable to try
adjusting this in steps of 0.1 % until a successful étalon lock is
achieved. If needed, the étalon voltage behaviour may be
monitored on a CRO by selecting
Etalon Photodiode
from the
drop down menu of one of the two user configurable Monitor
outputs.
2.
An iterative combination of both
BRF Tune
and
Etalon Tune
controls may be needed to fine tune SolsTiS to the required
output wavelength while making sure that the
Etalon Tune
control is set towards the middle of its adjustment range (i.e.,
away from either end of its adjustment range, where the laser
may be close to jumping the next étalon mode).
Note!
Once the
Etalon Lock
has been engaged,
this circuit will resist attempts to tune SolsTiS’
wavelength via the
Etalon Tune
. Be sure to
disengage the
Etalon Lock
before trying to tune
SolsTiS via the
Etalon Tune
.