We study experimentally the transmission of an electro-magnetic waveguide in the frequency range from 160 to 300 GHz. Photo-mixing is used to excite and detect the fundamental TE10 mode in a rectangular waveguide with two orders-of-magnitude lower impedance. The large impedance mismatch leads to a strong frequency dependence of the transmission, which we measure with a high-dynamic range of up to 80 dB, and with high frequency-resolution. The modified transmission function is directly related to the information rate of the waveguide, which we estimate to be about 1 bit per photon. We suggest that the results are applicable to a Josephson junction employed as a single-photon source and coupled to a superconducting waveguide to achieve a simple on-demand narrow-bandwidth free-space number-state channel.
@article{arxiv.1909.08976,
title = {Analysis of a single-mode waveguide at sub-terahertz frequencies as a communication channel},
author = {Marc Westig and Holger Thierschmann and Allard Katan and Matvey Finkel and Teun M. Klapwijk},
journal= {arXiv preprint arXiv:1909.08976},
year = {2020}
}