I try to generate nanosecond pulses with a Pockels cell. The experiment scheme is:
The laser beam, passing through the optical isolator, enters the Pockels cell, then through the Glan-Thompson polarizer enters the fast photodetector (2 GHz). Photodetector and oscilloscope are impedance matchend (50 Ohm), but I have to use sma-bnc adapter. Also I use galvanic isolator of the cell driver. So Even when the laser beam is obstructed, the oscilloscope shows the presence of a transient every time the cell is triggered. I think there is electrical induction on the wires. How can I shield the driver correctly? The photodetector already has a shield. Thanks.
The nanosec pulse correspond to ~30cm light propagation distance, so the setup naturally becomes UWB transmitter/ receiver.
I would first try to replace photodetector by 'SMA short' or matched load to see whether it is photodetector or SMA cable or directly the oscilloscope that picks the EMI.
In my experience, SMA connectors are not great in such case, N-type connectors are much better (they have separate inner ground circle), so one should use them if possible.
Also, there is a known technique of ferrite sleeves/ common mode toroids but it does not seem to be efficient at nanosec pulses.
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