December 2019 28 LDC-3706 Series Laser Controller
Operating a Laser in Constant Current (Current) Mode with Analog
Modulation
1. Plug the LDC-3706 into an appropriate AC power source supplying the correct mains voltage
and frequency for the instrument (refer to the rear panel for the correct ratings)
2. Turn on the LDC-3706. The laser output will be disabled at power up and the unit will
automatically configure its parameters to the state which existed when the power was last
shut off.
3. If the temperature controller is required please refer to the section below on temperature
control prior to enabling the laser current output.
4. Press the LASER MODE soft button until the CURRENT LED is illuminated.
5. Select the maximum output current range for the laser by pressing the RANGE soft button
under LASER RANGE. For best performance select the lowest range that allows the laser to
be run at the maximum desired output current.
6. Press LASER under PARAMETER to adjust the laser current limit, voltage limit, power limit
(if applicable), calibration PD value, photodiode reverse voltage bias, and LD TEC error link.
Also make sure to adjust to either LOW or HIGH bandwidth mode, based on the maximum
required modulation frequency. The maximum frequency bandwidth for each range can be
found in the specifications in Chapter 1.
7. Press the soft button under MOD to enable the input BNC jack and connect the voltage
signal that will be superimposed on to the output. See the Specifications in Chapter 1 for
details on transfer function and maximum bandwidth. Note that all limits also apply to the
modulated output, thereby protecting the laser in all operating modes.
Be sure not to exceed the specified modulation voltage level or damage to the
instrument may result.
8. Under the ADJUST section press the LASER soft button and use the knob to adjust the
output current to the desired output. Press the ON soft button under LASER MODE. It is
advised when using a new laser or connection to the laser to set the output to zero prior to
enabling the output. Once the output is enabled slowly ramp the current to the desired
output.
9. The user can display measured voltage, photodiode current, calculated photodiode power,
and current setpoint on either the left or right side of the LASER display by pressing the
LEFT or RIGHT display soft buttons under the LASER display.
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