Light beams bearing orbital angular momentum (OAM) are used in various scientific and engineering applications, such as microscopy, laser material processing, and optical tweezers. Precise topological charge control is crucial for efficiently using vortex beams in different fields, such as information encoding in optical communications and sensor systems. This work presents a novel method for optimizing an emitting micro-ring resonator (MRR) for emitting vortex beams with variable orders of OAM. The MRR consists of a ring waveguide with periodic structures side-coupled to a bus waveguide. The resonator is tunable due to the phase change material Sb₂Se₃ deposited on the ring. This material can change from amorphous to crystalline while changing its refractive index. In the amorphous phase, it is 3.285 + 0i, while in the transition to the crystalline phase, it reaches 4.050 + 0i at emission wavelength 1550 nm. We used this property to control the vortex beam topological charge. In our study, we optimized the distance between the bus waveguide and the ring waveguide, the bending angle, and the width of the bus waveguide. The optimality criterion was chosen to maximize the flux density of the radiated energy emitted by the resonator. The numerical simulation results proved our method. The proposed approach can be used to optimize optical beam emitters carrying OAM for various applications.

An intraoperative diagnostic is a vital tool in modern surgery, and it improves the accuracy of tumor removal and reduces the likelihood of damage to healthy tissue. The paper considers increasing the accuracy of intraoperative diagnostics through multimodal methods: a combination of Raman spectroscopy and optical coherence tomography. It is shown that when used in conjunction with machine learning methods, the accuracy of the diagnostic system can be up to 98%. To further increase the accuracy, it is advisable to consider other types of Raman spectroscopy as part of a multimodal system.

The paper proposes a novel mathematical model of emission and spatial distribution of the optical radiation that carries orbital angular momentum, i.e. optical vortex beams, by microring resonators (MRRs). The considered MRR features a diffraction grating formed by holes perforated on its surface, facilitating the emission of vortex beams. The emission process is analytically examined using the theory of scattering electromagnetic waves by permittivity inhomogeneities, applying the Rayleigh approximation. We use the vector representation of the electromagnetic fields utilizing the Kirchhoff–Helmholtz integral theorem to describe the field spatial distribution. Unlike already known ones, the proposed model considers the impact of the MRR and the diffraction grating parameters, including its inhomogeneities configuration, on the emitted field. Numerical simulations conducted using the Finite Difference Time Domain method in the Ansys Lumerical 2020 R2.4 environment support the validity of the proposed analytical model. The results we obtained enable us to identify the area with the highest energy flux density from the resonator at a specified distance analytically and with high accuracy. This capability can greatly streamline and enhance the development and optimization of vortex field emitters based on micro-ring resonators.

Subject of study. Microring resonators with a radiation-emitting diffraction grating formed by periodic holes on their surface are investigated. Aim of study . The aim of this study is to develop mathematical models for the emission and spatial radiation distribution of the optical vortex beams carrying orbital angular momentum, produced by microring resonators. Method . The process of optical beam radiation from a microring resonator is described using the general theory of electromagnetic wave scattering by dielectric inhomogeneities in the Rayleigh approximation. Optical vortex beam forming is considered in terms of the vector representation of electromagnetic fields based on the Kirchhoff–Helmholtz integral theorem. Numerical simulations were performed in the Ansys Lumerical software environment. Main results . Analytical expressions have been derived to determine the spatial distribution of the electric field and the energy flux density emitted by a microring resonator depending on the configuration of the resonator and the parameters of the periodic holes on its surface, as well as the region of the maximum energy flux density, depending on the topological charge of the generated optical vortex beam. To verify and confirm the accuracy of the second part of the mathematical model, additional numerical simulations were performed in the Ansys Lumerical environment. Practical significance. The findings of the study can be utilized to enhance the efficiency of communication channels and optimize them in promising optical information technologies.