Calibration Of Optical Power Display - THORLABS LDC200C series Operation Manual

LDC200C Series
"I " increases to the limit "I
LD
ð If the connection to the photodiode is interrupted in constant power mode, the laser current
"I " increases to the set current limit "I
LD
ð If the injection current "I
not longer correspond to the specifications for normal operation. However, the set maximum
current "I " cannot be exceeded.
LIM
ð If the connection to the laser diode is interrupted during operation, the output is switched off
automatically. LED "LASER ON" (F7) extinguishes, LED "OPEN" (F4) lights up and a short
beep is heard.
ð If the output is switched on while the interlock is closed and there is no laser diode
connected, at first the LED "LASER ON" (F7) lights up and the output switches on. Then the
LDC2xxC recognizes the missing laser diode, switches the output off, the LED "LASER
ON" (F7) extinguishes and the LED "OPEN" (F4) lights up. Connect the laser, then press
"LASER ON" (F8) - the LED "OPEN" (F4) extinguishes and the laser diode current output
switches.
ð The laser current can be modulated via the connector "MOD IN" (R3) - see section
Analog Modulation
Changing the "I " setting range
PD
With potentiometer "PD RANGE" (F25) the full scale of the adjustment knob (F9) can be set in
order to ease the setting of the operating point in constant power mode even with low
photodiode current. The photodiode current range depends on the type of the LDC2xxC
controller:
· LDC200CV: 0.6 mA to 2 mA
· LDC201CU, LDC202C, LDC205C: 3 mA to 10 mA
· LDC210C, LDC220C, LDC240C: 6 mA to 20 mA
· Turn the potentiometer "PD RANGE" (F25) completely counter clockwise.
· Turn the adjust knob (F9) completely counter clockwise.
· Select constant power mode "P" (key "CONST" F24), connect the laser diode and the
photodiode and switch on the laser current by pressing the key "LASER ON" (F8).
· Set the desired photodiode current with the knob (F9).
If the desired operating point cannot be reached even if the knob (F9) is turned completely
clockwise (i.e. I > 0.6 mA), turn the potentiometer "PD RANGE" (F25) clockwise until the
PD
desired setting range has been reached.
Note
A change of the "PD RANGE" (F25) leads to a change of the power set value in CP mode. In
constant current mode the potentiometer "PD RANGE" is without function.

3.5 Calibration of Optical Power Display

Additionally to the photodiode current "I
displayed. To achieve a correct optical power display, a calibration (potentiometer "CAL" - F12)
must be carried out:
ð Select constant current mode "I" - key "CONST" (F24).
ð With the knob (F8), set the laser current "I
output power of the laser diode is known, e.g. from the data sheet of the laser diode. You
16
" after the output is switched on.
LIM
LIM
" is limited by the selected current limit "I
LD
.
17
".
", the optical power of the laser diode can be
PD
" to an operating point for which the optical
LD
", ripple and noise do
LIM
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