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Fun fact: these laser pulses are so short they are no longer a single wavelength. They have a spectrum due to the uncertainty principle. And at this short of a time scale, it’s pretty broad.

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I might regret asking, but could you explain this? (At a physics 101 level)

Time and energy are “conjugated” quantities: the more one is sharp, the more the other one is broad (it’s the same concept as Fourier transforming a Gaussian: the more it’s peaked the more the transform is broad). In order for the time duration of the pulse to be so short, it must have a broad uncertainty in energy, which for light is the same as a wide spectrum of colors.

That’s why it’s very tricky to find materials for mirrors and lenses when working with these short pulses: they must work well over a large range of frequencies. If they happen to absorb some more than others not only they would burn, but they would also change the temporal profile of the pulse.

Thanks very much ziofill. Is this the same thing as the Heisenberg Uncertainty Principle? Or is there something else similar for time and energy?

Yes, it's the same thing in the sense that even if you work with a single photon the same applies (if you want its wavefunction to be narrow in time, its energy uncertainty must be broad)

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