helical resonators?

An ECL nand gate can make a very fast on/off oscillator; 1.5 to 2.5 cycles for switching, and clean.

There are a variety of optical things that might work without requiring something as slow as physical motion, e.g. high birefringence fibre and a liquid crystal retarder or a Pockels cell. The classical fibre phase modulator is several turns of fibre wrapped round a piezoelectric cylinder, but that's still a kilohertz sort of thing.

Cheers

Phil Hobbs

I was just kidding. It would be too big and expensive, and I need to close the phase lock loop in a few microseconds.

Why not build a multi-phase oscillator, then at "go time", pick the closest phase output and phase lock that one?

Reminds me of the first time I designed a driver for a Pockels cell. All I had was a (beefy) 12V rail so I put HV warnings on there. Dutifully in English and Spanish. Fired it up ... "Hey guys, it works!" ... wanted to move it closer to the unit ... *BZZZZT* ... Ouch! A Chinese engineer could not resist razzing me that I should have put the warning on there also in Chinese and German.

Presumably, a phase delay that is adjustable? Reflect a beam from the top of a mercury column in a thermometer. A fever thermometer with 1" indication range will give the retroreflection about 150 ps of adjustment range.

Extra points for filling the void above the mercury with a suitable index-matching medium, and for getting the whole assembly ROHS approved...

Gotta watch out for those dangerous 12V rails.

:-)

I had built a thingamagic that made around 200V from that. Pulsed ...

The Pockels things were wounted on the board and their contacts exposed everywhere.

Use gallium; AFAIK it is not on the shit list.

Corrodes like mad though.

Cheers

Phil Hobbs