Self-imaging of orbital angular momentum (OAM) modes in rectangular multimode interference waveguides

Abstract

We study the propagation of orbital angular momentum (OAM) modes in rectangular multimode waveguides. Due to the multimode interference effect, an OAM mode input forms self-images at certain propagation distances. As OAM modes can be decomposed as the superposition of a pair of quarter-wave phase-shifted even and odd modes, their symmetry properties lead to two different self-imaging categories - forming the OAM-maintaining and the field-splitting self-images. We analyze these phenomena using multimode interference theory, and establish the rules governing the OAM-maintaining self-imaging, which allows the multi-mode interference waveguides to be used as OAM mode splitters and couplers.

Higher Order Mode Conversion From Berry's Phase in Silicon Optical Waveguides

“…In a fashion analogous to HG and LG beams in paraxial optics, it has been shown that superpositions of higher order modes of rectangular dielectric waveguides, quasi-HG modes, can form quasi-Laguerre-Gaussian (quasi-LG) modes exhibiting optical vortices and possessing orbital AM [23], [24]. Such modes have been used to demonstrate on-chip OAM generators, multiplexers, and multimode interference devices [25]- [27]. Below we compute the angular momentum ( + ) of such quasi-LG modes in units of ℏ per photon and numerically demonstrate higher order mode conversion in the out-of-plane waveguide in Fig.…”

Recent Advances in Generation and Detection of Orbital Angular Momentum Optical Beams—A Review

“…The idea of getting the necessary distribution at the output of the device already touched upon TE 01 and TE 10 eigenmodes being mixed with π/2 phase shift. The rectangular WGs assisting multiple transverse modes and keeping symmetry in two orthogonal transverse directions are also proposed in [ 171 ].…”

Modeling and Optimization of Vortex Modes Propagation in Rectangular Dielectric Waveguides

“…More recently, in order to provide miniaturization, robustness, repeatability in massive production, cost and energy efficiency of the systems involving optical vortices, significant attention of research groups has been focused on developing photonic integrated circuits (PICs) for generation, processing and detection of vortex modes. As a result, a number of integrated OAM-based solutions have been proposed, which in general can be subdivided into three groups depending on the approaches used for vortex beam generation and transmission: i) out-of-plane solutions [31]- [44]; ii) in-plane solutions [45]- [49], and iii) solutions based on three-dimensional (3D) PICs [50], [51]. In the current paper, we focus on planar (two-dimensional) waveguides, which are compatible with standard PIC fabrication processes.…”

“…Up to now this approach is much less elaborated and only a few publications on are known [45]- [49]. In [45]- [48], the solutions for generation of OAM beams with azimuthal order of ±1 have been proposed and numerically modelled.…”

“…These solutions involve the use of the system of silicon waveguides and directional couplers [45], a waveguide with a single longitudinal trench [46], a hybrid plasmonic waveguide [47], and integrable quarter-wave plates [48]. In [49], authors theoretically investigated propagation and self-imaging of OAM modes in multimode interference waveguides and showed that such devices can be used as OAM mode splitters and couplers. In the papers [52], [53], we have experimentally demonstrated for the first time in-plane propagation of the 1 st order quasi-TE vortex modes in a planar rectangular polymer waveguide.…”