The terahertz range holds potential for ultra-wideband wireless communications applications, including 6G and beyond, due to large and under-utilized spectral bandwidth. Terahertz communications will benefit from channelization as individual channel bandwidths will be reduced, thereby simplifying baseband and intermediate-frequency (IF) circuits. Furthermore, passive multiplexers enable power combining of several independent sources at different frequencies, which is beneficial to terahertz technology because the achievable transmission distance is restricted by factors including limited power and strong path loss.
Researchers have introduced the concept of gratingless tunneling multiplexers and employed it to realize a diplexer, triplexer, and 4×1 multiplexer for terahertz waves—all of which are both highly compact and efficient owing to in-slab beamforming technique.
The simplicity of this technique offers versatility. A designer may essentially specify a desired in-slab magnitude distribution that is mediated by a single physical parameter: waveguide-to-slab separation. Furthermore, the curvature of the waveguide may be optimized, e.g. using Gerchberg–Saxton hologram-like techniques to project near-arbitrary beam shapes into the slab.