BME Bergmann

Bergmann Messgeräte Entwicklung KG


This is a small quarterwave switch that can typically be used in regenerative amplifiers for 800nm working with two Pockels cells, one for injecting the pulse into the amplifier, the other for extracting it after amplification. The principle of this amplifier layout is shown in the figure above.

When both Pockels cells are at zero voltage state, the seed pulse makes just one round trip before being ejected again. To trap the pulse, Pockels cell no. 1 must be switched to quarterwave after
the pulse has just left Pockels cell no. 1 and the QWP before it. When the pulse returns from its round trip, the polarization will not be rotated anymore, thus the pulse is trapped.

To eject the pulse from the amplifier, Pockels cell no. 2 must be switched to quarterwave voltage just after it has left Pockels cell no. 2. Thus after returning from the next round trip in the amplifier, the polarization will be roptated by 90 degrees, thus ejecting the pulse.

The oscilloscope trace shown here was taken by applying quarterwave voltage to the Pockels cell, measuring the transmission in a single pass setup. Risetime is 3.5nsec, which is a good deal faster than necessary for the usual round trip time in these amplifiers of 10nsec.

This q-switch driver is very small, needs only one supply voltage and a trigger. Presently we fabricate two versions,
Close-Coupled or connected to the Pockels cell with 30cm cable
Of course, at cutomer request we can make any other design.