An optical module includes a chamber capable of being evacuated and a mirror in the chamber. The mirror includes a plurality of individual mirrors. Each individual mirror includes: a mirror body including a reflection face; a support structure; and a thermally conductive portion that mechanically connects the support structure to the mirror body. For at least one individual mirror, the thermally conductive portion includes a plurality of thermally conductive strips arranged radially, adjacent thermally conductive strips being separated from each other, and each of the plurality of thermally conductive strips connecting the mirror body to the support structure. For at least one individual mirror, an actuator is associated with the mirror body, the actuator being configured to displace the mirror body relative to the support structure in at least one degree of freedom.