CREATION OF AN OPTICAL XYZ COORDINATE SYSTEM USING BIDIRECTIONAL BLAZING FROM A SYMMETRICAL TRIANGULAR-GROOVE GRATING IN A CONICAL DIFFRACTION MOUNT

An xyz beam splitter is described that uses a diffraction grating upon which light is incident in a plane parallel to the grating grooves to produce symmetric conical diffraction into the +/-1 orders, with all higher orders being suppressed or evanescent. The +/-1 orders are mutu ally orthogonal when the wavelength/grating period ratio lambda/LAMBDA = 1/square-root 2, independent of the angle of incidence phi. Orthogo nality of the +/-1 orders with the direction of incidence occurs at ph i = arctan(1/square-root 2) = 35.264-degrees. By choice of a symmetric triangular-groove profile (isoceles with a 120-degrees apex angle), b idirectional blazing occurs into the desired +/-1 orders, with little or no light appearing in the vestigial 0 order.