A spectral purity filter includes a body of material, through which a plurality of apertures extend. The apertures are arranged to suppress radiation having a first wavelength and to allow at least a portion of radiation having a second wavelength to be transmitted through the apertures. The second wavelength of radiation is shorter than the first wavelength of radiation. The body of material is formed from a material having a bulk reflectance of substantially greater than or equal to 70% at the first wavelength of radiation. The material has a melting point above 1000° C.