Herein, we have discussed three major methods which have been generally employed for the generation of optical beams with orbital angular momentum (OAM). These methods include the practice of diffractive optics elements (DOEs), metasurfaces (MSs), and photonic integrated circuits (PICs) for the production of in-plane and out-of-plane OAM. This topic has been significantly evolved as a result; these three methods have been further implemented efficiently by different novel approaches which are discussed as well. Furthermore, development in the OAM detection techniques has also been presented. We have tried our best to bring novel and up-to-date information to the readers on this interesting and widely investigated topic.

Herein we propose a design of a wavelength-tunable integrated vortex beam emitter based on the silicon-on-insulator platform. The emitter is implemented using a PN-depletion diode inside a microring resonator with the emitting hole grating that was used to produce a vortex beam. The resonance wavelengths can be shifted due to the refractive index change associated with the free plasma dispersion effect. Obtained numerical modeling results confirm the efficiency of the proposed approach, providing a resonance wavelength shift while maintaining the required topological charge of the emitted vortex beam. It is known that optical vortices got a lot of attention due to extensive telecommunication and biochemical applications, but also, they have revealed some beneficial use cases in sensors. Flexibility in spectral tuning demonstrated by the proposed device can significantly improve the accuracy of sensors based on fiber Bragg gratings. Moreover, we demonstrate that the proposed device can provide a displacement of the resonance by the value of the free spectral range of the ring resonator, which means the possibility to implement an ultra-fast orbital angular momentum (de)multiplexing or modulation.

We propose and numerically verify a design approach to a grating coupler (GC) for in-plane generation and propagation of quasi-TE vortex modes with azimuthal order ±1 within photonic integrated circuits (PICs). In the considered GC design example, silicon nitride waveguides with silica substrate and cladding are used. The shallowly etched grating is illuminated by the incident optical beam from a standard single-mode fiber. We optimize the GC design parameters to maximize the purity of orbital angular momentum (OAM) mode first for the case of a theoretical ideally fabricated grating, and then consider a more practical case of GC design, when the etching resolution is limited. The numerical modeling results show possibility of the vortex mode generation with >96% purity of the target OAM state ±1 at the wavelength 1550 nm. The proposed design, compatible with the standard nanofabrication process, provides a simple, compact and robust solution for various potential PIC-based applications of OAM beams.

We propose and numerically verify a design of the photonic integrated circuit for in-plane generation of a 1st azimuthal order vortex mode in dielectric rectangular waveguides. Radiation is introduced into the proposed structure in a standard way through two grating couplers. Applying a mode coupling and specific phase shift, a field with the required amplitude-phase distribution is formed directly in the output waveguide. The geometric dimensions of the device are simulated and optimized to fit the technological parameters of the silicon-on-insulator platform.

In this article we present the brief review of different scenarios of using the photonic integrated circuits (PIC) in the swept-source optical coherence tomography (SS-OCT) with different degree of integration and propose implementation of PICs on the Si/Ge manufacturing technology with integrated analogous balanced photodetectors. The first PIC implementation contains two arms for processing backscattered light and light reflected in “off-axis” mode on the same chip. We present results of simulation of such PIC that demonstrate its functionality. The second PIC implementation provides functionality for the optical processing of the backscattered signals and includes integrated narrow-band filter based on the adjustable unbalanced Mach-Zehnder interferometer for reseting the digital signal processor in the beginning of the every period of the frequency sweep. Implementing the SS-OCT functionality on the PIC will make possible to reduce the cost of the final device, as well as significantly reduce its geometric size, which is an important factor that provides portable use.

We present design of photonic integrated orbital angular momentum (OAM) emitters consisting of access waveguides and ring resonator with top grating made from holes. Access waveguides are coupled to the resonator using “pulleycoupler” scheme. The device is designed for silicon-on-insulator (SOI) manufacturing platform. We simulated singlemode resonator with one access waveguide and shown that it emits two OAM modes in out-of-plane regime. Than we simulated multimode resonator with two access waveguides and shown that it emits up to four OAM modes. The implementation of OAM emitter based on the ring resonator has specific resonance spectrum therefore such devices are WDM compatible. Compactness of such device allows using it in photonic integrated circuits.