Abstract
We study experimentally the transmission of an electromagnetic 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 quantum channel.
Highlights
An important problem in communication technology is the transmission of a coded message, from an initial point via a channel to a final point, with minimal error in receiving and decoding the message
For a 3D cavity, the relative energy loss in surface defects scales inversely proportional to its size,5 which is dependent on the propagating mode because of the mode-dependent current distribution at the cavity walls
The frequency-tunable electromagnetic signal, in the appropriate frequency range of 160–300 GHz, is generated and detected by superimposing the outputs of two 780 nm distributed feedback (DFB) lasers in a beam combiner (BC) and illuminating two GaAs photo-mixers connected at the output of the beam combiner via polarization maintaining fibers (PMF), with one photo-mixer acting as a coherent terahertz source (S) and the second one as a coherent terahertz detector (D)
Summary
An important problem in communication technology is the transmission of a coded message, from an initial point via a channel to a final point, with minimal error in receiving and decoding the message. Electro-magnetic transmission lines, such as an optical fiber or a waveguide, are attractive as a communication channel because compared to free space, they minimize the radiative information loss. We analyze experimental results on the transmission of a waveguide at subterahertz (THz) frequencies in the context of this information communication-effectiveness. For a 3D cavity, the relative energy loss in surface defects scales inversely proportional to its size, which is dependent on the propagating mode because of the mode-dependent current distribution at the cavity walls. This type of technology has been developed many years ago in the field of astronomical detectors for applications at significantly higher frequencies. Developed for the astronomically important range of hundreds of gigahertz and for other sophisticated 3D submillimeter waveguide circuits, the technology appears suitable for use in quantum networks as well
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