There's some kind of filter at the entrance slit of the spectrometer.
Blue laser light grazes the baffle in the spectrometer:
Blue laser light at the entrance slit appears orange:
Red/orange halo around blue core of blue laser light after passing
through the entrance slit:
Blue laser light from fiber optic shown on white paper:
White light shown through entrance slit appears yellow:
Note: In the laser there's also some kind of filter
after the pinhole but before the laser feedback beamsplitter.
Laser output feedback sensor:
