Laser Timing with the BME_G02

Jitter-Free Control of a Femtosecond Lasersystem

shown below is typical example of a fs-laser system, an oscillator with two amplifiers, the first stage running at 10Hz, the second stage running at 1Hz. This demonstration has been derived from a diode pumped fs laser system built at the university of Jena, Germany.

A photodiode picks up the oscillator 76MHz signal which is fed into the external clock/trigger input of a BME_SG02 card. Using the fs-oscillator as the external clock 7 separately delayed outputs have to be fired synchronously to the arriving laser pulses with an allowed jitter of less than 0.5ns (actuallly the jitter is in this case only 50psec) and the output voltages fitted to specific needs of various devices.

The BME_SG02 master card sets the base repetition frequency of 10Hz. The BME_G05 slave cards have an output scaler that divides down the base repetition frequency of 10Hz by any integer number, in this case dividing it by 10 to get a repetition frequency of 1 Hz for the second amplifier. Thus it is possible to run the first amplifier at a repetition rate of 10Hz and the second at 1Hz without any additional device as well as exactly triggering further Pockels cells, pump lasers and instrumentation.

The timing of the laser system is as follows:

a)      Since the pumplaser of the 2. amplifier is a laser diode stack, it must be fired roughly 2msec before the laser pulse

b)      The flashlamp of the 1. amplifiers pumplaser must be fired 180usec in advance

c)      the Q-switch of the 1. amplifiers pumplaser must be fired 3usec in advance

d)      the timing of the pockels cells comes with the laser pulse and must be completely jitterfree for optimum performance of the laser system

 

As an option, it is possible to use the 50Hz line signal to derive the 10Hz base repetition rate of the laser system. Synchronizing the 10Hz base repetition rate of the laser system to the 50Hz line frequency might be advantageous, if line voltage variations can effect the output stability of the laser system.

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