MOGlabs DLC202, Manual, Page: 70 / 82

60 Appendix F. Laser head board
Note only one temperature sensor should be connected. For high
bandwidth
RF
modulation (see below), the diode should be con-
nected to the
SMA
connector (
P3
) rather than to the
MOLEX
HD1
.
Another very small circuit board, to connect directly to the diode,
is also available from
MOG
labs, with
SMA
and
MOLEX
connectors.
The
MOG
labs
DLC
does not provide a mechanism for optical power
control or measurement for diodes with an internal photodiode.
F.2 Grating pivot point compensation
From Rev 5, the laser headboard has two stack outputs, driven in
parallel, with a trimpot adjustment (
RT1
) of the voltage ratio between
the two. By driving two stacks, the effective grating pivot point can
be optimised to extend the mode-hop-free scan range.
The two
actuators can be driven equally so that only the cavity length will
vary, without rotation, or with a large ratio so that the grating rotates
while translating.
LENS
OUTPUT BEAM
LASER DIODE
GRATING
PIVOT
STACK
(PRIMARY)
STACK
(SECONDARY)
GR
AT
IN
G M
OU
NT
Figure F.2: Schematic of a Littrow-configuration
ECDL
with two piezo
stack actuators controlling the grating angle and cavity length. Scanning
the primary stack will rotate the grating and change the cavity length. If a
second actuator is added, the change in frequency due to the rotation and
the cavity length change can be synchronised to extend the mode-hop-free
scan range.