[dguest]

Photomultiplier tubes have a solid state counterpart [1] but there's still a lot of use for the vacuum tube version.

[1]: https://en.wikipedia.org/wiki/Silicon_photomultiplier

[HansHamster]

And Hamamatsu (and some others) still produce and sell photomultiplier tubes. The microchannel plate PMTs are pretty nifty things [1]. You can get single-digit picosecond time resolution out of them. [1]: https://www.hamamatsu.com/us/en/product/optical-sensors/pmt/...