Efficient mid-Infrared vortex beam generation using optical waveguides integrated with micro-spiral phase plates. (13th September 2019)

• Record Type: Journal Article
• Authors: Zhou, Junchao; Lin, Pao Tai
• Is Part Of: Journal of optics. Volume 21:Number 10(2019)
• Publication Date: 2019-09-13
• Subjects: Laguerre–Gaussian mode -- mid-Infrared -- vortex beam; Optics -- Periodicals; 535.05
• DOI: 10.1088/2040-8986/ab3b25
• Languages: English
• ISSNs: 2040-8978

Abstract

Abstract: Vortex beam generation from a mid-infrared photonic chip was numerically demonstrated by engineering the phase front of a waveguide mode. Multi-level micro-spiral phase plates (SPPs) consisting of N segments were patterned on the waveguide facet. The micro-SPP introduced an annular phase change by 2 π that converted the Hermite–Gaussian (HG) waveguide mode into Laguerre–Gaussian (LG) mode at topological charge ∣l∣ = 1. Using a 3D finite difference time domain simulation, we resolved the near-field optical phase map next to the micro-SPP and its far-field beam profile projected from the waveguide surface. The vortex beam formation was spectrally dependent. A uniform and symmetric donut-shaped pattern corresponding to an ideal vortex beam was created at λ = 3.1–3.3 μ m. In addition, the HG → LG mode conversion efficiency was improved by increasing the number of segments, N . Thus, our micro-SPP enabled present photonic circuits to create vortex beams, which is critical for the development of optical interconnection and broadband communication.