# Ultrashort Optical Pulses

If an ultrashort optical pulse has a complex wavefunction with central frequency corresponding to a wavelength = 585 nm and a Gaussian envelope of RMS width of 6 femtoseconds, how can I calculate how many optical cycles are contained in the pulse width?

## The Attempt at a Solution

Not too sure where to begin. I don't understand how a width can be measured in seconds. If it had been provided as a length, I would assume that one needs to simply divide that length by two times the wavelength to get the amount of cycles.

## Answers and Replies

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When you say of something "in two minutes drive from here", you refer to a distance in terms of time.

So then I suppose I can multiply it by the speed of light to get a distance, and then divide accordingly to get the answer?

That sounds right. The only issue is that with this sort of duration one cannot really talk of a particular frequency, but I guess that's what the problem wants you to neglect.

Sounds good. Thanks for the help.