The first 532nm laser tested was a small 5mW pointer from Thorlabs.
It is mounted on a Thorlabs 6 axis mount. This allow very good
positioning of the laser spot at the center of the microscope field.
This laser does not require any beam expander because the beam width is
already 5mm diameter. This is enough for a good focusing. The main
problem with this laser is his multi lines spectrum as can be seen on the
graph below. The two lines above 535 nm can be eliminated by the laser
line filter. The triplet at 531-532 nm cannot be modified by a filter.
It is nevertheless possible to get some Raman spectra with such a laser
but the resolution is reduced and extra peaks could arise in the
spectrum if the Raman lines are too narrow as illustrated below.
Comparison of spectra obtained with the multi
wavelengths Thorlabs laser and the single line laser. As the Raman peaks
of Enstatite are rather broad, the spectra with both laser are similar
and no peak splitting is observed.
Calcite spectrum with double peaks due to the multi