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 mutually orthogonal when the wavelength/grating period ratio
, independent of the angle of incidence ϕ. Orthogonality of, the ±1 orders with the direction of incidence occurs at
. By choice of a symmetric triangular-groove profile (isoceles with a 120° apex angle), bidirectional blazing occurs into the desired ±1 orders, with little or no light appearing in the vestigial 0 order.
© 1993 Optical Society of America
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