Optical notch filter apparatus and method therefor

An optical notch filter apparatus for attenuating light of a predetermined wavelength, the apparatus comprising:

• a dielectric optical element having a layer of metal disposed upon a surface thereof so as to form a metal/dielectric interface;
• a dielectric medium adjacent the layer of metal, the dielectric medium having a dielectric constant different from a dielectric constant of the dielectric optical element;
• wherein, when in use, light of a p-polarised state and the predetermined wavelength following a first propagation path so as to be incident upon the metal/dielectric interface is attenuated under conditions that support surface plasmon resonance;
• and
• at least one polarisation modifying optical element arranged relative to the dielectric optical element so as, when in use, to translate the state of polarisation of light of an s-polarised state to the p-polarised state, thereby permitting light at the predetermined wavelength having both the p- and the s-polarised states to be attenuated.