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? 2. Relevant equations 3. 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.