Synrad Model 48 Laser
Control Using the 9500 Series
Pulse Generators

AN0002

Application Note By STEVE BIRRELL

Summary

The 9500+ Series Pulse Generators provide a multiplex function which is ideal for providing the necessary tickle pulse, in addition to a variety of operational modes useful for controlling the laser.

QC Family

QC 9512+, QC 9514+, QC9518+

Introduction

Enabling and disabling the second channel will enable/disable laser emission.The pulse generator channel outputs can be operated in a number of modes (continuously, burst, single shot, duty cycle). This allows the laser to be pulsed continuously or for a controlled number of pulses. Individual channels may also be controlled by the gate input for synchronizing to an external signal.

Four or eight channel pulse generators may be used to synchronize the laser to instruments, video, and/or stages. This allows control of a complete experimental setup from one instrument.

The figure on the following page shows a 5 kHz tickle pulse multiplexed with a PWM pulse operated in the duty cycle mode (3 pulses on, two pulses off). The bottom pulse is a sync signal programmed to precede the laser pulses by 30us.

Many RF excited CO2 lasers, such as the Synrad Series 48, use a PWM command signal to control the laser energy and require a short `tickle' pulse to pre-ionize the laser gas. The tickle current keeps the laser ionized but below lasing threshold and any increase in the pulse width provides enough energy to result in laser emission. This allows the laser to respond predictably and almost immediately to changes in the PWM control signal. The Series 48 specifies a 1us, 5kHz pulse to generate the tickle current. A PWM signal from 1% to 95% controls the output power.

The 9500+ Series Pulse Generators provide a multiplex function which is ideal for providing the necessary tickle pulse, in addition, to a variety of operational modes useful for controlling the laser. Control of the laser is done by multiplexing two channels: One channel is used to generate the 1us, 5kHz tickle pulse; and the second channel is used to generate the PWM output pulse.

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