An electron microscope (10) is adapted to enable spectroscopic analysis of a sample (16). A parabolic mirror (18) has a central aperture (20) through which the electron beam can pass. The mirror (18) focuses laser illumination from a transverse optical path (24) onto the sample, and collects Raman and/or other scattered light, passing it back to an optical system (30). The mirror (18) is retractable (within the vacuum of the electron microscope) by a sliding arm assembly (22). An adjustable kinematic mount (44) defines the inserted position of the parabolic mirror (18). A second parabolic mirror (104) is provided to direct the scattered or generated light towards an optical analyser. The parabolic mirrors are positioned in an aberration cancelling orientation and such that they compensate for inaccuracies in the position of the sliding arm assembly (22).