High absorption in a wide frequency band has attracted considerable interest since their potential applications in frequency spectrum imaging systems and anti-radar cloaking. In this paper, a polarization-independent, ultra-broadband and omnidirectional terahertz absorber is proposed, fabricated and evaluated. It is experimentally demonstrated that an over 95% absorption can be obtained in the frequency range of 0.75~2.41 THz. Attributing to the multi-frequency destructive interference between the layers and the impedance-matching condition of the grating, five successive absorption peaks at 0.88 THz, 1.20 THz, 1.53 THz, 1.96 THz and 2.23 THz merged into a ultra-broadband absorption spectrum.

For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.

Based on the symmetric, asymmetric atom-photon couplings and the phase difference between two separated atoms, single-photon transport properties in an optical waveguide coupled with two separated two-level atoms are theoretically investigated. The transmission and reflection amplitudes for the single-photon propagation in such a hybrid system are deduced via a real-space approach. Several new phenomena such as phase-coupled induced transparency, single-photon switches, symmetric and asymmetric bifrequency photon attenuators are analyzed. In addition, the dissipation effect of such a hybrid system is also discussed.

Due to the excellent spectral efficiency and inherent resistance to multipath fading effect, OFDM has been widely adopted in Digital video broadcasting-terrestrial (DVB-T). However, as a multi-carrier transmission technique, there is sampling frequency offset (SFO) in the OFDM systems, which will seriously degrade performance of demodulation by resulting in interference between adjacent sub-carriers (ICI) and demodulated phase deviation. In this paper, to achieve correction of phase errors and solve the problem that OFDM signals cannot be correctly demodulated for complex constellation when SFO exists, we propose an adaptive sampling frequency tracking and demodulated phase error compensation scheme based on synchronization symbol information of OFDM signals. Numerical results supported by simulations are provided to show that the proposed scheme in an ADSL environment indicate great performance improvement of demodulation.