Timing.
… lasers inject their energy within nanoseconds, compared with milliseconds for spark plugs.
That’s what makes it interesting for focus fusion.
I don’t know whether they’re strong enough to ionise the switch fill gas as required. But multiple shots possibly can add up (maybe not):
The laser is not strong enough to light the leanest fuel mixtures with a single pulse. By using several 800-picosecond-long pulses, however, they can inject enough energy to ignite the mixture completely.
