Generation of mid-infrared vortex beams by 3-D printed polymer phase plates

Abstract

Light carrying vortex beam characteristics were demonstrated in the mid-infrared (mid-IR) region using polymer based spiral phase plates (SPP). The SPP was fabricated through three dimensional (3-D) direct laser writing method, which can construct the optical phase according to the mid-IR wavelength of interest. The fabricated SPP consisted of 32 layers and the layer thickness was precisely adjusted between 100 and 600 nm to create 2π helical phase change. The ideal SPP structure and the gradient optical phase diagram were designed and simulated by the finite-difference time-domain (FDTD) method. Characteristic vortex beam profiles with a ring-shaped pattern and a sharp centric dark spot were experimentally illustrated at a wavelength range of λ = 3.1–3.3 µm. The formation of mid-IR OAM through high throughput 3-D writing technology provides critical integrated components to explore quantum photonics and optical communications.