Semiconductor lasers tunable and multi wavelength lasers
A tuneable laser is a laser whose wavelength of operation can be modified in a controlled way. While all laser gain media allow little moves in output wavelength, just a few types of lasers allow consistent tuning over a significant wavelength range.
There are numerous sorts and categories of tuneable lasers. They exist in the gas, fluid, and solid state. Semiconductor lasers are usually monochromatic because the electronic levels are disseminated in continuous energy bands.