# Multi wavelength lasers

At the lab I work at, we have a laser capable of emitting light at a spectrum of wavelength. As far as I know, this spectrum is continuous, in that it can emit from 800 nm to 1200 nm for example.

Conventional lasers emit a single wavelength of light due to the emission signature of specific atoms, which is clearly not the case here. My question is how does a laser like this work? How can it emit variable wavelengths?

First, the spectrum isn't really continuous because you need a standing wave in the laser cavity. But the difference between them is $\frac{c}{2L}$ where L is the cavity's length which makes the spectrum look continuous in a regular spectrum analyzer, for example a $30cm$ long resonator will have a difference of $500MHz$ which is negligible compared to the optical frequency.