THORLABS MCLS2-CUSTOM User Manual page 21

MCLS2-CUSTOM 4-Channel Laser/SLD Source
Turning the Source Off
When completely powering down an enabled unit, first press and release the ENABLE ALL button (if all sources
are enabled), or each of the individual ENABLE switches for the channels, and then turn the POWER key switch
counterclockwise, which will turn OFF the entire unit. Anytime the unit is turned OFF and then turned back ON,
the lasers and SLDs in the unit will be disabled until an individual ENABLE button or the ENABLE ALL button is
pressed.
Modulating a Source Output
The Modulation Inputs can be used to modulate the light source output or set the light source output remotely
using a 5 V power source via the BNCs located on the back panel of the unit. The 5 V maximum inputs correspond
to the maximum output of each channel. The modulation input is also additive with the internal laser or SLD set
point. If too much voltage is applied, on its own or in combination with the internal setpoint, internal current
limiting will prevent damage to the diode and the diodes will be immediately disabled.
There are two methods of modulation available. The first method is enabling the laser or SLD and setting the
percent output to 0.00 %, "Standby," allowing utilization of the full 0 to 5 V input range. This mode allows more
flexibility, but the drawback is that a minimum voltage will be required to operate above the threshold current for
laser sources. The second mode is to set the output to the desired minimum as an offset or to utilize Threshold
Mode and adjusting the output one step up from 0.00 %. The internal drive and the external modulation level are
additive so the analog modulation voltage will need to be limited to less than 5 V, but a DC offset will not be
required.
Modulating from Standby Operation – Set the control knob on the front panel to its full counterclockwise setting
for standby mode (Output 0.00 %). Apply an appropriate signal between 0 and 5 V to the Modulation Input for
the desired channel. Determine the DC offset by increasing the voltage slowly until a large power jump is seen on
the output. An easier method it to apply a 1 V
then the bottom edge is no longer clipping. This method requires applying the laser or SLD output to a
photodetector and monitoring with an oscilloscope. Next maximize the amplitude so that the peak is 5 V or less
as desired.
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DO NOT turn the power key switch off until laser/SLD is disabled. Failing to disable
all outputs first can damage the unit permanently.
sinusoid and adjust the DC offset until the sinusoid appears and
pp
Modulation from Standby Operation
100
80
60
40
20
0
External Input Amplitude
Time
Chapter 4: Operation
TTN353580-D02