MOGlabs CEF, Manual

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38
Appendix B. Laser head board
B.2 B1047/B1240 headboards
The B1047 and B1240 provide high-speed active modulation of the diode
current. They use 500 MHz opamps and very low latency circuitry to re-
duce phase delay to around 12 ns for the B1240. The B1047 allows for
closed-loop bandwidth of about 1.2 MHz while the B1240 can achieve
about 4 MHz (in both cases, without phase advance), which is helpful in
achieving sub-Hz linewidth reduction by locking to a high-finesse optical
cavity. The B1240 also allows direct-ground connection or buffered; the
latter is about 10% slower but reduces problems with ground-loop noise.
The B1240 is not suitable for diodes with high compliance voltage, typi-
cally diodes with wavelength below 600 nm.
Note that connection to the SMA input will reduce the diode current, even
if the control voltage is at zero.
C
5
C
4
R
4
R 7
C 6
R 5
R 6
C 11
R 12
D1
R 10
C 8
R 14
U
3
R
1
C
3
Q
1
R 2
C 1
C 2
R 3
R 11
P2
U1
P5
U2
R 13 C 7
R 9
SMA
P3
P4
P6
L1
L2
P1
AC DC
LED
Thermistor
Piezo1
Laser diode
TEC
+
–
+
–
+
–
+
–
+ –
Piezo2
C
1
C
6
C
7
R
1
5
R
3
R
4
R
6
R 2
D1
R 5
C 5
R 16
C 2
R 1
R
1
4
C 8
R 17
C
4
U
1
R
7
U
3
U
2
R 10
R 11
R 12
R 13
P6
P5
R 8
RL1
R 9
C 3
SMA
P9
P10
P11
L2
P8
L1
AC DC
Buff
LED
Thermistor
Piezo1 Laser diode
TEC
Piezo2
Figure B.3:
B1047 (left) and B1240 (right) enhanced laser head boards. Jumpers
at top left can be configured for AC or DC coupling. The B1240 has an additional
jumper “Buff ” for direct or buffered (differential) ground coupling, shown connected
for differential coupling; change to pins 1 and 2 for direct. Modulation input via
SMA connector, sensitivity 2.5 mA/V. Connectors are Hirose DF59.