# Minimum spread of frequency and wavelength in neodymium laser

What is the equation linking the minimum spread in wavelength and frequency of a pulsed laser, in relation to the lasers pulse time and operational wavelength.

For example:

If a Neodymium laser operates at a wavelength of 1×10–6 m and the laser is operated in pulsed mode, emitting pulses of duration 3×10–11 s.

What is the minimum spread in frequency and wavelength?

• Neodymium laser isn't really a good example I think. It's (as far as I recall) far from limit, which is given by Fourier transform. I don't remember exact equations now, but look-up Fourier-limited lasers pulses and you will get what you need. It's somewhat resembling Heisenberg uncertainty principle binding time and bandwidth. – Jarosław Komar Dec 19 '14 at 12:07