Measuring the spectrum of a laser diode emission with a resolution of a few pm is necessary when addressing different kinds of issues: the use of a laser source for metrological applications based on interferometry or other physical phenomena such as the Raman effect or atom cooling usually requires pure spectra or, at the very least, good knowledge of the true spectral characteristics.
Laser users and integrators often have a huge choice of laser sources but with limited information on their laser spectrum unless they use an intrinsically pure laser, as for instance a HeNe laser. This can lead to serious difficulties in understanding the results of metrological setups or industrializing products. And here lies the need to evaluate source quality, the true operating range or component uniformity.
Measuring the spectrum of a laser with high resolution is also a necessity when developing new and innovative lasers.