Abstract: Photonic switch working in Momentum-Division-Multiple-Access (MDMA) mode for microwave and optical wavelengths based upon the measurement of the spin, orbital angular momentum and total angular momentum of the involved photons. For the optical wavelengths Dove prisms and holograms are used in form of a Mach-Zehnder-Interferometer as selectors; for the microwave wavelengths phased-array antennas with double orthogonal dipoles act as selectors.

Abstract: A Fourier transform spectrometer for use, among others, for sensing gases or liquids includes two polarizers, a birefringent optical component interposed between the two polarizers and a detector. Light from an extended source is substantially polarized by a first of the two polarizers, split into divergent beams by the birefringent optical component, and again caused to converge by the birefringent optical component so that, after passing through a second of the two polarizers, the light forms an interferogram in a plane behind the birefringent optical component where the detector is situated. The Fourier transform spectrometer is thereby provided with a way of forming an interferogram of the light from the extended source without a lens or a second birefringent optical component. This improves the field of view of the spectrometer and is likely to reduce its cost.