December 2019 24 LDC-3706 Series Laser Controller
Bandwidth: This selects between low-bandwidth and high-bandwidth modes for the
modulation input. The maximum frequency for each bandwidth mode is listed in the
specifications in Chapter 1.
Photodiode Responsivity: The photodiode responsivity in
µA/mW for the laser system
currently being controlled is set here. The default value is 0.0
µA; end user is required to
enter a value for laser power conversion.
Photodiode Bias Voltage: The LDC-3706 Laser Controller provides an adjustable reverse
bias of 0 – 5 VDC for the photodiode. The bias can be adjusted by the front panel under the
Parameter Laser selection or via GPIB/USB. The default value is 0.0V; end user is required
to enter a value for photodiode current readings.
TEC Disable Output:
“LD TEC Error” when enabled will disable the current source
output if the temperature controller exceeds the temperature limits or if the TEC output is
disabled either by the user or due to an error. When this mode is active, the laser current
source will not enable unless the TEC output is enabled.
Brightness: This allows the user to select a level of brightness for the front panel displays.
Values between 1 (dim) and 10 (bright) can be selected from the front panel. This value can
also be controlled remotely (see Chapter 4).
Laser Calibration:
This menu allows for calibration of the laser diode current output and
reading, laser diode voltage readings, and the monitor diode current reading. See
chapter 5 for more details.
STORE Button – Stores instrument parameters for control mode, setpoints, limits, sensor type,
sensor calibration constants, and PID values for bins numbered 1 – 10.
RECALL Button – Recalls instrument parameters for control mode, setpoints, limits, sensor type,
sensor calibration constants, and PID values for bins numbered 1 – 10. Recall bin 0 will reset all
parameters to the factory defaults.
Non-volatile memory is used for saving the instrument parameters. When a store operation is
performed, all of the current instrument parameters are stored to a "bin" number (1 - 10). When that
"bin" number is recalled, the instrument configuration is recalled to the stored values.
To enter the STORE/RECALL mode, press either the STORE or RECALL button which will display
the current “bin” number in the bottom of the screen. The current “bin” number will be flashing and
the ADJUST knob can be used to select a new “bin”. The store or recall operation is performed
when the SET button is pressed. If the SET button isn’t pressed after three seconds the LDC-3706
instrument will time out and the new “bin” number will not be stored or recalled.
Modulation State: The Modulation State parameter allows the user to select whether the Laser
Modulation Analog input is enabled or not. For best results, when not modulating the laser
through the BNC input port on the front of the instrument, make sure that the Modulation State
is set to the OFF condition by pressing the Enable button until the ENABLE LED is unlit.
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