modulator box

Modulates, what else? :)

It's a box.

If you've got a modulator, you can stick it inside theah.

RL

Well, thanks for clearing that up.

Generates an arbitrary waveform when triggered, and drives a 2-stage e/o modulator that was mounted inside. It was used in the NIF fusion system.

I'm sure the e/o modulator is not inside that one; it's too valuable.

We made the arb waveform by summing 120 Gaussian impuses spaced 250 ps apart. You can see the Gibbs Ears in the white waveform.

Yes. I was surprised to find that pic online, with the posters on the end of the rack.

The 120 Gaussian impulses were spaced optimally to get a flat-top rectangular waveform. But if you try to make a square pulse from those impulses, you get the Batman effect, the ears on either end.

Fortunately, the real waveform doesn't need the sharp corners.

Nowadays, one would just use a screaming fast DAC.

The next-gen modulator uses a Tek arb to make the waveform, and we post-process that. I had to invent a new way to bias some $300 distributed amplifier chips. DAs are usually specified for telecom use, where the waveform is DC-balanced data, 8b10b or some such, but we wanted big short pulses.

What’s the wavelength? I might be interested.

Cheers

Phil Hobbs

We modulate at 1053 nm, which is optically amplified, tripled to UV, and amplified some more.

The triplers are giant, beautiful, pinkish slabs of glass. Take the NIF tour if you are ever around Livermore.