In the 1960's I worked for a company that produced spectrometers. For most purposes we supplied xenon lamps as the light source. I do not remember the range thes lamps cover but we normally worked with the uv and the near uv regions. All mirrors were first surface. All the lenses and windows were quartz or equivlant. Most calibrations were done using varions compounds that had known adsorbance lines or floursed (spelling) at known wave lengths. Most of the equipment we produced was used in research labs, either in universities or medical research labs.