Synrad Pulstar P100 Series, Руководство оператора, Страница: 55 / 110

technical reference
3
7 Synrad Pulstar p100 operator’s manual
Controlling laser power
The Controlling laser power section includes subsections:
■ Tickle pulse
■ Pulse Width Modulation (PWM)
■ Command signal
Important Note: Except for bench testing, we do not recommend using a UC-2000 Controller with
the Pulstar OEM p100 laser. The automatically-generated tickle signal from the UC-
2000 may interfere with the laser’s pulsing performance.
To control the p100’s output power and pulsing characteristics, thoroughly review this section, Controlling
laser power , for an understanding of the signal parameters necessary to control Pulstar pulsed lasers.
Tickle pulse
Note: Because all Pulstar OEM p100 lasers incorporate a built-in tickle generator, there is no need to
supply external tickle pulses. The application of external tickle pulses may affect the p100’s puls-
ing performance.
Tickle pulses pre-ionize the laser gas to just below the lasing threshold so that a further increase in pulse
width adds enough energy to the plasma to cause laser emission. Tickle pulses cause the laser to respond
predictably and almost instantaneously to PWM Command signals, even when there is considerable delay
(laser off time) between applied Command signals.
Internal circuitry monitors the incoming PWM signal and determines the amount of time the laser was
on (lasing) during the last 200 microsecond (µs) interval. If the laser’s on time was greater than the preset
tickle value, then no tickle pulse is generated because the PWM signal was sufficient to maintain a plasma
state. If no PWM signal was applied during the 200-µs measurement period (or was
shorter
than the preset
tickle value), internal circuitry generates a tickle pulse such that the laser always receives a pre-set amount
of RF drive averaged over any 200-µs interval.
Pulse Width Modulation (PWM)
Pulse Width Modulation, or PWM, controls laser power by varying the duty cycle of Pulstar’s RF ampli-
fiers, which in turn control the time-averaged RF power applied to the laser. Typically, Pulstar p100 laser
output follows the PWM input with a rise and fall time constant of ~ 40 µs; however, the laser cannot
precisely follow PWM input signals of the “On” pulse is less than 40 µs in duration. The laser’s percentage
of optical output increases as duty cycle increases (at a constant PWM frequency) or as PWM frequency
decreases (at a constant duty cycle).
Pulstar p100 lasers are designed to operate at Command signal frequencies ranging from a single-shot up to
100 kHz; however, the choice of PWM frequency depends on the user’s specific application.