OWNERS MANUAL | Cobolt 06-01 Series | D0136-K DECEMBER 2018
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should be applied to modulate the laser, and the duty cycle is set by the input signal. The on/off modulation socket
takes a 3.5 mm stereo audio plug. The plug should be connected as shown in the figure below.
In Cobolt Monitor
™
there is a tick box “On/Off Modulation”, which indicates when on/off modulation is active. When
this is the case, all other options are greyed out (although the previous mode remains checked, as the laser remembers
which state it was in previously). The laser automatically detects when an on/off modulation signal is present and
enables
on/off modulation, so there is no need for the user to check the “On/Off Modulation” box manually. In the
box next to this tick box the user can set the peak power level that the laser will modulate up to. This is set in the
factory to the laser’s nominal maximum power level. If analog or digital modulation
is enabled when On/Off
modulation is enabled, the laser will operate in both simultaneously. See below for more information about
modulation mode combinations.
NOTE
The on/off modulation feature should never be used as remote interlock connector. A remote
interlock socket is provided for this purpose on the laser head
Digital modulation
Digital modulation is the fastest modulation type; it has the largest bandwidth and shortest rise time. Digital
modulation requires a 0-5V TTL input signal applied to the digital modulation input female SMA connector on the
laser head, and the duty cycle is set by the input signal. The diode current is modulated in a square wave.
To enable digital modulation using the Cobolt Monitor
™
software, select “Modulation Mode”, and “Digital” under
Modulation Type. You can set the peak power level that the laser wil
l modulate up to by first pressing the “More”
button which opens up a new control window and then enter your preferred value in the box to the right of the
“Modulation Mode” check box.
Analog modulation
Analog modulation allows direct control of the laser power by an input signal. This allows the laser to be modulated
with arbitrary waveform at limited bandwidth. To enable analog modulation using the Cobolt Monitor software,
select “Modulation Mode”, and “Analog” under Modulation Type. The input signal sho
uld be connected to the Analog
BNC connector on the key control box (CDRH model) or the dedicated pins on the 15-pin D-SUB (OEM model). The
laser is calibrated so that a 1 V input gives 100 % of the laser’s nominal power level (for frequencies above 1 MHz
it
may be necessary to increase the amplitude of the analog signal up to 1.5 V). Note that the laser may give more power
if a voltage larger than 1 V is used. Although the current is clamped to a safe current limit to prevent damage, the user
must nevertheless avoid overdriving the diode so that it gives more than the nominal power level. Specifications and
diode lifetime are not guaranteed above nominal power, which is stated on the
manufacturer’s identification label
on
the laser head. Measure the input voltage before connecting to the laser head.
Ground
+5V
!
