Abstract: Various medical conditions in a subject may be diagnosed by comparing the concentration of a diagnostic species such as ethane in breath samples from a subject from different stages of the breathing cycle. Using phase sensitive measurement of absorption of IR laser radiation, very small concentrations of the diagnostic species can be measured. Apparatus for collecting breath samples from different stages of the breathing cycle is also disclosed.

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 contains a birefringent optical component, removing the need for a Michelson interferometer used in conventional instruments. A suitable birefringent element such as a Wollaston prism, is used to introduce a path difference between two light polarisations. Use of an extended light source so that all areas of the birefringent component are illuminated simultaneously ensures that different positions on the birefringent component correspond to different path differences between the two polarisations. A Fourier-transform of the resulting interferogram at the detector results in the spectral distribution of the input light being obtained. The use of an extended light source permits a Fourier-transform spectrometer with no moving parts to be achieved.