Sub-wavelength custom reprogrammable active photonic platform for high-resolution beam shaping and holography

Abstract

High-quality holograms constructed from a modulated waveguide require a periodicity beyond a quarter of the wavelength. Classical electro-optic modulation would be at first glance excluded to achieve this goal, as this requires (metal) electrodes closer than a few tens of nm to the waveguide. However, we enable this in our Active Photonic Platform (APP) by using a metamaterial constructed from a conductive oxide and an isolating nitride to obtain matching refractive index in the waveguide cladding region over the visible wavelength range.

State-of-the-art waveguide-based holographic displays achieve ultra-low noise by using mode conversion as active driving mechanism. Recent work aims to combine this with the precise control offered by subwavelength modulation to create a new generation of APP’s. Our approach employs the electro-optic effect to modulate a slab waveguide by an electrode cladding layer. Crucially, this method enables the use of subwavelength sized electrodes leading to similar sized refractive index modulation, that furthermore is reprogrammable at video rate.

We propose a Barium Titanate waveguide electro-optically modulated on sub-wavelength scale by a metamaterial electrode. We present a driving scheme, inspired by signal analysis, that leverages electric field simulations and nonlinear optics to achieve any desired spatial modulation. We employ finite difference time domain simulations to create dynamic image generation under ideal and realistic scenarios. We considered all relevant design parameters enable the creation of a reprogrammable APP capable of high-quality beamforming, directional sensing, and video-rate holography.