I wondered the same thing. Acousto-optic modulators and deflectors have been commercial items since the late 1970s/early 1980s. I used them in that era. They

I wondered the same thing. Acousto-optic modulators and deflectors have been commercial items since the late 1970s/early 1980s. I used them in that era. They were even intrinsic parts of laser systems, sitting within the cavity to create pulses of various kinds. There's also a 50 year history of measuring dynamics in gas and condensed phase systems by the transient grating method which uses laser pulses to generate temporary gratings in all sorts of media. Two short (nanoseconds and on down) cross in a sample (solid, liquid, gas, flame, etc.). They generate an interference pattern and the fringe separation depends on the crossing angle. At points of high intensity, some kind of excitation is created and the refractive index gets modulated by the fringe pattern forming a grating. Now bring in a third pulse at a later time and it will scatter off of this grating. The grating will decay with time as the excitation relaxes due to whatever physical or chemical process is under study. Change the delay between the excitation and probe pulses to get a decay curve which is the observable to be fitted, modeled, compared with theory, etc.