A method of modulating an optical beam.

摘要

A method of modulating an optical beam (1) and apparatus for use in such a method are described. An etalon structure (2) is provided which has an absorption edge in the vicinity of the wavelength of the optical beam (1) and which comprises material of a smaller band gap, for example gallium arsenide, sandwiched between layers of material of a larger band gap, for example aluminium gallium arsenide, so that the smaller band gap material forms a quantum size effect confinement region for electrons and holes. The smaller band gap material may consist of layers (4) separated by barrier layers (3) of the larger band gap material so that the layers (4) form quantum wells. The optical beam (1) is directed through quantum size effect confinement region of the etalon structure (2) and a polarised control optical beam (5) is directed at the etalon structure (2) perpendicular to a direction of quantum size effect confinement of the etalon structure (2), thereby causing the optical beam (1) to be modulated by the control optical beam (5).