Wireless Signal Transmission at the 2 and 3 THz-Band Enabled by Photonics-Based Transmitter and Hot Electron Bolometer Mixer

We have demonstrated terahertz (THz) wireless transmission of quadrature phase-shift keying (QPSK) signals at 2 and 3 THz-bands. Despite higher atmospheric attenuation at frequencies above 1 THz, it might be applicable for short-range wireless communications. The proposed system is composed of a photonics-based transmitter using an optical comb source and a heterodyne receiver system using a hot electron bolometer mixer (HEBM). In the transmitter, THz signals are generated by photomixing of optical carriers extracted from broadband optical combs. The receiver system consists of a quasi-optical HEBM and a phase-locked THz quantum cascade laser (THz-QCL) as a local oscillator (LO). Although the emission power of the photonics-based transmitter was on the order of tens of nW, it could be received with sufficient SNRs due to high sensitivity of the HEBM. Demonstrations of signal transmission were carried out with 2 and 3 THz-band. Optical carriers were modulated with basic LTE FDD R9 uplink signals with full filled QPSK, and converted to THz signals, transmitting to the receiver system. The THz signals were successfully demodulated, in which error vector magnitude (EVM) values of the demodulated signal was about 22% and 30% for 2 and 3 THz-band, respectively.