Terahertz aperture SNOM mapping of metamaterial coupled resonators

Metamaterials have emerged as the basis of a novel optoelectronic platform operating in the terahertz (THz) range, due to their versatility and strong light-matter interaction. The necessary design of efficient modulators and detectors requires a detailed investigation of metamaterial resonances and their interplay with an active medium, e.g. graphene. An aperture-SNOM (a-SNOM) system based on picosecond THz pulses was used to investigate the spectral characteristics of a set of lithographically tuned metamaterial coupled resonators. This approach allowed the mapping of the supported E-field of each resonator a few microns from the device plane, yielding bonding and antibonding modes reminiscent of electromagnetic induced transparency

Digital Chunk Processing with Orthogonal GFDM Doubles Wireless Channel Capacity

A novel physical layer (PHY) transmission technique for increasing the channel capacity of transmission, termed as Orthogonal Generalized Frequency Division Multiplexing (OGFDM), has been proposed, investigated and evaluated in this paper. A combination of the Digital Hilbert Filter (DHF) with Generalized Frequency Division Multiplexing (GFDM) has been shown to double wireless channel capacity for each transmitted frequency sub-carrier at acceptable Bit Error Rate (BER) limits. By making use of the great properties of Hilbert transforms, orthogonality is achieved between the traditionally non-orthogonal GDFM subcarriers improving the BER and wireless channel capacity of the transmission. The OGFDM seems to combine the attributes of GFDM and Orthogonal Frequency Division Multiplexing (OFDM) in one sustainable system. The proposed solution achieves orthogonality between the filters of adjacent frequencies of subcarriers instead of between the frequencies of subcarriers themselves. Also, an OGFDM system model is presented, based on which, the relation between the main filter parameters and the system BER and channel capacity performance is specified in a wireless electrical back-to-back transmission system. Finally, by means of simulations, the impact of applying the proposed advanced filters on the aggregated system performance of the BER and channel capacity is shown in an Additive White Gaussian Noise (AWGN) wireless channel