Is it possible to work with large laser spot sizes on a Raman microscope?

Yes.  Certain system, such as the LabRAM HR, can be configured with adaptive optics such as the LineScan or DuoScan™ which allow laser spots to be created which can have dimensions up to 270 x 270 µm2 (depending on the objective being used).

Standard Raman microscopes are limited to spot sizes in the order of 0.5-10 µm (depending on the laser wavelength and objective being used), which is due to the optical path of the collimated laser beam through the objective.  While such small spot sizes are ideal for analysis of microscopic features and offer excellent spatial resolution when combined with true confocal optics, they can be limited for bulk or macroscopic analysis.

The LineScan and DuoScan™ optics have scanning mirrors in the microscope which rapidly rastor the microscopic laser spot over the sample either in a line (for LineScan) or in a user defined line or rectangle (for DuoScan™).  These allow an average spectrum to be acquired from the line or rectangular area, and thus allows a Raman microscope to be used for macro analysis.

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