Adjusting The Bias Voltage For The Monitor Diode; Selecting Constant Current Or Constant Power Mode - THORLABS ITC8 Series Operation Manual

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2.2.5 Adjusting the bias voltage for the monitor diode

If required, the monitor diode may be driven with a bias voltage up to 10 V.
Before switching on bias voltage make sure that the photodiode
If the photodiode is forward biased with a voltage, a current will flow
through it that could damage or even destroy it.
The bias voltage can be set by adjusting the parameter:
U =
BIA
in the channel menu of the module.
(Refer to chapter 2.2.2, "Changing parameters" on page 31)

2.2.6 Selecting constant current or constant power mode

The current modules ITC8xxx offer two operating modes for the laser diode.
In constant current mode the laser diode current is kept constant. If the temperature
of the laser changes the optical power will change too since the efficiency of the laser
will change.
If the set-up uses a monitor diode receiving a certain part of the laser light the
measured monitor diode current can be kept constant by adjusting the laser diode
current correspondingly. Changes in temperature of the laser will cause a change of
its efficiency but the laser diode current is re-set for the optical power to remain
constant. This is called constant power mode, Pconst.
Select the parameter
MODE =
and toggle between Pconst (CP) and Cconst (CC).
For "constant power" mode a monitor diode is necessary in the set-up.
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© 2010 Thorlabs
Attention
polarity is set correctly (inverse direction).
Functions in the channel menu
NOTE
33