A probe for examining a sample (5), the probe comprising an emitter (1) for emitting radiation, a detector (1) for detecting radiation and a dielectric member (3) configured to direct radiation from the emitter (1) to the sample (5) and to direct radiation reflected by the sample (5) to the detector (1), wherein in use, the dielectric member (3) occupies at least half of the radiation path length from the emitter (1) to the sample (5) to the detector (1).