English: Spectrum of a en:Helium neon laser taken using an Ocean Optics HR2000 spectrometer [1] by bouncing the laser off of a white benchtop and guiding the diffuse reflected light directly into the spectrometer. The emission spectrum of the HeNe laser is even more monochromatic than seen here (it is typically around a mere 2 picometers in bandwidth) and the broadening of the peak in this spectrum is actually a result of the imperfect optics and scattering of light inside the spectrometer which results in some light being detected on the parts of the (linear CCD) sensor which surround the central peak. A very high resolution spectrum of a en:Brillouin scattered HeNe laser can be seen here [2] for reference. Spectrum taken by me.