O P E R A T I O N S
Functions and Features
32
LDC-3700 Series
C H A P T E R
2
A standard BNC connector on the rear panel of the LDC−3700B Controller is available for connecting
any standard BNC terminated cable.
Figure 2.4
LDC−3700B Series Rear Panel
Modulating the Controller Laser Current Source
The LDC−3700B Series Laser Diode Controller allows a modulated signal to be superimposed on
the LASER injection current. For example, assume you are using an LED for your experiment
where you need operate the led in constant current at P
OP
= 1 mW, and a modulated injection
current from 3 to 30 kHz. The experiment requires the LDC−3724B’s laser controller to be
configured for the 200 mA range, high bandwidth mode with a limit of 175 mA. The allowable
bandwidth of the modulated signal, defined as the 3 dB roll off point, is dependent on the LDC−
3700B Series family member, the LASER current range, and the LASER mode (constant current
low/high bandwidth). See the section, LASER CURRENT SOURCE SPECIFICATIONS, in Chapter
1 for external analog modulation bandwidth specifications.
Setting up the controller for a modulated laser injection current is easy. The (
MOD
)
EXTERNAL
connector (BNC), on the front panel, is the input for the modulated signal. The modulation port input
impedance is 10 k
Ω
. The transfer function (mA/V) shown is for the LDC 3724B. This transfer
function varies by model and laser drive current output range. The transfer function for the low and
high current ranges of the LDC 3714B are 5 mA/V and 10 mA/V, and 200 mA/V and 400 mA/V, for
the LDC−3744B.
Set the LDC−3700B in Constant Current High Bandwidth Mode by selecting
I
HBW
in the
LASER
MODE
section of the front panel. Do this by toggling the
SELECT
push button until the
I
HBW
1, 2 TE MDL +
1, 2 INTLK
TE CONTROLLER
CURRENT SOURCE
THERM RANGE
SENSOR SELECT
THERM
PD BIAS
ADJUST
TRIGGER
OUTPUT
N / A
LM335
AD590
100 A
µ
10 A
µ
9 ANLG GND
8 SENSE +
9 LSR ANOD
50 mA/V
20 mA/V
MOD
EXTERNAL
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