First tests with laser pointer


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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.

Test spectra

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 lines laser