The sampling strobe generation work is taking some strange twists (details to come), but one branch I'm exploring is solidly traditional: step recovery diodes (SRDs). I have some real ones on order (not quite as unobtainium as I thought), but in the mean time, it turns out that the bog-standard 1N914/1N4148 type diodes can function as decent, if slow, SRDs.

In case you're wondering, those long leads are there for a reason (see below). There's not much to the test circuit - the diode is just shunted across the output of a pulse generator and measured with an oscilloscope.

Here's the measured output from the diode. Channel 2 (blue) is a copy of the output of the pulse generator (from another output channel) for reference. During the positive swing of the pulse, current flows through the diode. When the input polarity is reversed, the diode continues to conduct for a brief time, then suddenly "snaps off." You can clearly see the rapid drop in conduction, with the waveform becoming almost vertical at this scale.

Zooming in, we see that the rapid drop has a fall time of around 800 ps (ignore the automated measurement, it's looking at the overall drop from the top of the pulse). The pulse generator has a fall time of around 8.5 ns (compare the blue trace), so the diode has sharpened the fall time considerably.

This diode is very slow compared to diodes designed as SRDs, but it illustrates the concept.

Those long leads? They add some inductance which peaks the pulse a little. Here's the same diode with short leads. Note how the bottom edge of the pulse droops a little. In this regime, the inductance of a few cm of wire matters, and sometimes can be used to advantage. Of course, I found this by accident :-)

There is a paper out there on the internet somewhere that used a 1N4148 diode like this to produce a strobe for a moderate-speed sampling gate. Now I can't find it again, and it doesn't appear to be in my collection of papers. When it turns up again, I'll post the link here.