QBY-BT GaN Pockels cell drivers

QBY-BT is an encased version of QBY-4001, a Pockels cell driver by OEM Tech based on GaN transistors. It provides bipolar voltage pulses (3-4 ns rise/fall) on the outputs to control the birefringence of an electro-optical crystal to change the polarization state of light passing through. It is a compact bench-top model with fast switch to obtain short pulses starting from 10 ns. The QBY-BT is equipped with internal controller to manage the output and with cooling fan, which made it possible to increase the max. rep. rate in five times at the maximum voltage in comparison with QBY-4001.

One can adjust pulse amplitude, pulse repetition rate and width manually or by external controlling device through RS-485 interface. Pulse controlling TTL signals J1 and J2 (see the picture below) are generated internally under controller regulation. Simultaneously, the module generates an output synchronisation signal (TRIGGER OUT) with a definite time shift towards to J1, this could help to syncronise the whole system. It is also possible to connect an external pulse generator to set an operating frequency and pulse width.

Output voltage is up to 4 kV, max. rep. rate strongly depends on selected output voltage value and on load capacitance. We recommend therefore to use the shortest possible cables and choose a Pockels cell with lower capacitance.

The module requires +24 V DC power supply.

Please, note that by bipolar device an output pulse voltage U is formed by applying +U/2 to positive output wire and –U/2 to negative.

The module was designed to work in set-reset scheme when a base voltage level equals to zero. Non-periodic pulses are also possible, set by pulse generator.

A pockels cell driver on GaN is very sensitive to load capacitance. In order to keep its performance close to datasheet values, one needs to minimize the load capacitance, numbers less than 5 pF are appreciated.