The LiNbO3 Slab Waveguide: A Platform for Terahertz Signal Generation, Detection, and Control

Abstract

We provide an overview of the terahertz (THz) polaritonics system, an on-chip platform for the generation, detection, and control of THz-frequency electromagnetic waves. The “chip” is a thin slab of lithium niobate crystal whose nonlinear and electro-optic properties directly enable the functionality. We first discuss dielectric slab waveguiding, which determines THz wave behavior in the polaritonics system. We then cover the generation of broadband and narrowband THz waves with an ultrafast laser pulse. The next topic is time-resolved imaging, which lets us record movies of the THz waves as they propagate at the speed of light with sub-cycle temporal and λ/100 spatial resolution. The final experimental tool discussed is laser machining, which makes it possible to fabricate photonic elements directly in the lithium niobate slab. Using these techniques, we show THz waves interacting with a variety of microstructures including a mirror, diffraction grating, waveguide, interferometer, photonic crystal, and metal antenna. These structures enable wave steering, guiding, spectral and spatial filtering, amplitude modulation, field enhancement, and sub-wavelength field localization. The broad capability set makes the polaritonics platform a promising one for future high-speed devices in optical communications and computation. The field enhancement and control also makes this an excellent platform for nonlinear THz spectroscopy.