In this paper, using a modified model of slowly varying amplitudes, a process of optics-to-THZ-conversion of vortex beams based on the nonlinear difference frequency generation in a medium with second-order susceptibility is considered. A theoretical substantiation of the law of topological charge conversion of vortex beams is given – the topological charge of the output THz vortex beam is equal to the difference of the topological charges of the input optical vortex beams. A simulation model of the processes under consideration is implemented.

It is proposed that a special optical device be used to connect the radio antenna array to a Radio-over-Fiber light guide line, which provides splitting optical signals into predetermined frequency bands. The field calculation within the device active region is done.

In this paper, we consider the process of fiber vortex modes generation using chiral periodic structures that include both chiral optical fibers and chiral (vortex) fiber Bragg gratings (ChFBGs). A generalized theoretical model of the ChFBG is developed including an arbitrary function of apodization and chirping, which provides a way to calculate gratings that generate vortex modes with a given state for the required frequency band and reflection coefficient. In addition, a matrix method for describing the ChFBG is proposed, based on the mathematical apparatus of the coupled modes theory and scattering matrices. Simulation modeling of the fiber structures considered is carried out. Chiral optical fibers maintaining optical vortex propagation are also described. It is also proposed to use chiral fiber-optic periodic structures as sensors of physical fields (temperature, strain, etc.), which can be applied to address multi-sensor monitoring systems due to a unique address parameter—the orbital angular momentum of optical radiation.

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The paper investigates the possibility of obtaining transparent bulk nanocrystalline pyroceram glass with a 3D-gradient of the refractive index for a mixer of an optical device to control the radiation pattern of an array antenna. The starting material was biphasic. Operating modes are described and photographs of the resulting samples are presented. An optimal method of treatment is identified, comprising the selected heating and cooling modes of samples. The analysis of the degree of deformation due to nanostructural processing of the samples is conducted. The resulting material will be used for the development of fiber-optic telecommunications systems.