Photochemistry and Spectroscopy Department

Institute of Physical Chemistry, Polish Academy of Sciences


The collimated beam of the excitation laser enters into the inverted microscope system that consists of a cylindrical lens (CL) and a cylindrical mirror (CM). The lens (CL) focuses the laser beam onto a slit focus located perpendicularly to the plane of Figure at point OC. This focus is imaged exactly at 1:1 scale onto the sample surface by a cylindrical mirror CM. The corrected excitation laser image has dimensions of 0.1 x 2 mm at the surface of the sample. The light scattered from the sample is collected through a concentric system of mirrors with a large aperture, 1,5 steradians. After reflections from the mirrors M1 and M2 the light impinges onto the slit of the MS monochromator. Here is formed a magnified image of the excitation sheaf. The magnification is 15-fold, thus the image dimensions are 1.5 x 3.0 mm. A field lens L creates the image of the mirror M2 on the monochromator grating. It allows to fully utilize the monochromator aperture, and to minimize light losses.The concentric system of the mirrors M1 and M2 has the curvature radius optimized to minimize spherical aberrations. Before taking Raman measurements the whole system is set so that the focus of the excitation beam fully overlaps with the back projection of the slit. For this purpose, a small microscope is used (on the left on the photograph). Under such conditions the signal is optimized by shifting the sample S along the system axis.