OWNERS MANUAL | Cobolt Skyra™ |
D0423-E JANUARY 2018
30 | 45
Continuous wave operation
Each laser line has two continuous-wave operating modes: constant power and constant current. The default mode
for each line is constant power. In constant current mode the laser runs at a set current level. In constant power
setting is used to regulate the output power level.
Laser 1 : DPL has an photodiode to monitor the power and actively adjust the current to maintain a stable output
power.
Modulation mode operation
Which modulation type to use?
Each laser line has three different modulation types: digital, analog and internal. These modulation types aim to cover
most applications the user may have, and they each have very different specifications.
Digital modulation allows for fast modulation speeds. Use digital modulation if you are modulating at high
speeds in a square wave.
Analog modulation is not as fast as digital, but has the advantage that the user can drive the laser with
arbitrary waveforms. Use this mode if you require arbitrary waveform.
Internal modulation allows the user to modulate the laser without an external modulation signal source.
Digital and Analog modulation can be used simultaneously in combination to give complicated output shapes such as
pulse bursts. These combinations are dealt with separately at the end of this section. Switching between modulation
types can be done using the Cobolt Monitor™ software or with direct commands.
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 male SMB connector on the laser
head, 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 will 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.
The power levels are controlled by the high and low current settings. The high current is set during manufacturing to
achieve up to 100 % of the nominal power in the ON state, at 1 kHz, 50% duty cycle. It is not always possible to reach
MLD
DPL
Digital modulation bandwidth
DC – 5 MHz
DC – 5 kHz
Analog modulation bandwidth
DC- 500 kHz
DC – 5 kHz
Internal modulation bandwidth
Up to 500 Hz
