Gratingless integrated tunneling multiplexer for terahertz waves

• Published in: Optica Vol. 8; no. 5; p. 621
• Main Authors: Headland, Daniel, Withayachumnankul, Withawat, Fujita, Masayuki, Nagatsuma, Tadao
• Format: Journal Article
• Language: English
• Published: 20.05.2021
• ISSN: 2334-2536; 2334-2536
• DOI: 10.1364/OPTICA.420715

The arrayed waveguide grating (AWG) is a versatile and scalable passive photonic multiplexer that sees widespread usage. However, the necessity of a waveguide array engenders large device size, and gratings invariably commute finite power into undesired diffraction orders. Here, we demonstrate AWG-like functionality without a grating or waveguide array, yielding benefits to compactness, bandwidth, and efficiency. To this end, we exploit optical tunneling from a dielectric waveguide to an adjacent slab in order to realize a slab-confined frequency-scanning beam, which is manipulated using in-slab beamforming techniques that we have developed in order to separate distinct frequency bands. In this way, we devise an all-intrinsic-silicon integrated 4 × 1 frequency-division terahertz multiplexer, which is shown to support aggregate data rates up to 48 Gbit/s with an on–off-keying modulation scheme, operating in the vicinity of 350 GHz. Our investigation targets the terahertz range, to provide a critical missing building block for future high-volume wireless communications networks.