Abstract
The revolutionary 5G cellular systems represent a breakthrough in the communication network design to provide a single platform for enabling enhanced broadband communications, virtual ...reality, autonomous driving, and the internet of everything. However, the ongoing massive deployment of 5G networks has unveiled inherent limitations that have stimulated the demand for innovative technologies with a vision toward 6G communications. Terahertz (0.1-10 THz) technology has been identified as a critical enabler for 6G communications with the prospect of massive capacity and connectivity. Nonetheless, existing terahertz on-chip communication devices suffer from crosstalk, scattering losses, limited data speed, and insufficient tunability. Here, we demonstrate a new class of phototunable, on-chip topological terahertz devices consisting of a broadband single-channel 160 Gbit/s communication link and a silicon Valley Photonic Crystal based demultiplexer. The optically controllable demultiplexing of two different carriers modulated signals without crosstalk is enabled by the topological protection and a critically coupled high-quality (
Q
) cavity. As a proof of concept, we demultiplexed high spectral efficiency 40 Gbit/s signals and demonstrated real-time streaming of uncompressed high-definition (HD) video (1.5 Gbit/s) using the topological photonic chip. Phototunable silicon topological photonics will augment complementary metal oxide semiconductor (CMOS) compatible terahertz technologies, vital for accelerating the development of futuristic 6G and 7G communication era driving the real-time terabits per second wireless connectivity for network sensing, holographic communication, and cognitive internet of everything.
The classical theory of modulation instability (MI) attributed to Bespalov-Talanov in optics and Benjamin-Feir for water waves is just a linear approximation of nonlinear effects and has limitations ...that have been corrected using the exact weakly nonlinear theory of wave propagation. We report results of experiments in both optics and hydrodynamics, which are in excellent agreement with nonlinear theory. These observations clearly demonstrate that MI has a wider band of unstable frequencies than predicted by the linear stability analysis. The range of areas where the nonlinear theory of MI can be applied is actually much larger than considered here.
We demonstrate the effectiveness of frequency selective surface filters in wireless communications at low terahertz (THz) frequencies. Full-wave simulations of pass-band filters designed at 270 GHz ...and 330 GHz are compared with measurements over 220-360 GHz, showing remarkable agreement. The filter spectral response is used to analytically model a THz filter-based wireless channel for modulated signals. In particular, numerical results and measurements for an OOK modulated signal are in good agreement for both free-space and filtered transmission at 14 Gb/s. In both cases, bit error rates (BER) as low as 10-10 are measured. This result demonstrates that the filters marginally affect the BER with respect to free-space, interference-free transmission, whereas interfering signals are strongly rejected. This result is demonstrated through a systematic evaluation of the BER in presence of an interfering signal with different carriers and amplitudes. Results confirm a strong filter rejection to interference carriers close to the filter central frequency. Conversely, without the filters the BER performance is fully compromised. Finally, we demonstrate numerically and experimentally that the constellation diagram for 104 Gb/s QAM-16 communication is not significantly affected by the filter. The investigated filters may provide a robust approach towards efficient spectrum management for future 6G wireless applications.
The discovery of the Fermi-Pasta-Ulam (FPU) recurrence phenomenon in the 1950 s was a major step in science that later led to the discovery of solitons in nonlinear physics. More recently, it was ...shown that optical fibers can serve as a medium for observing the FPU phenomenon. In the present work, we have found experimentally and numerically that in the low-dispersion region of an optical fiber, the recurrence is strongly influenced by the third-order-dispersion (TOD) term. Namely, the presence of TOD leads to several disappearances and recoveries of the FPU recurrence when the central frequency of the pump wave is varied. The effect is highly nontrivial and can be explained in terms of reversible and irreversible losses caused by Cherenkov radiations interacting with a multiplicity of modes sharing the optical energy in the process of its partition.
We experimentally test the universality of the Anderson three dimensional metal-insulator transition, using a quasiperiodic atomic kicked rotor. Nine sets of parameters controlling the microscopic ...details have been tested. Our observation indicates that the transition is of second order, with a critical exponent independent of the microscopic details; the average value 1.63±0.05 agrees very well with the numerically predicted value ν=1.58.
Using a three-frequency one-dimensional kicked rotor experimentally realized with a cold atomic gas, we study the transport properties at the critical point of the metal-insulator Anderson ...transition. We accurately measure the time evolution of an initially localized wave packet and show that it displays at the critical point a scaling invariance characteristic of this second-order phase transition. The shape of the momentum distribution at the critical point is found to be in excellent agreement with the analytical form deduced from the self-consistent theory of localization.
Anderson localization, the absence of diffusion in disordered media, draws its origins from the destructive interference between multiple scattering paths. The localization properties of disordered ...systems are expected to be dramatically sensitive to their symmetries. So far, this question has been little explored experimentally. Here we investigate the realization of an artificial gauge field in a synthetic (temporal) dimension of a disordered, periodically driven quantum system. Tuning the strength of this gauge field allows us to control the parity-time symmetry properties of the system, which we probe through the experimental observation of three symmetry-sensitive signatures of localization. The first two are the coherent backscattering, marker of weak localization, and the recently predicted coherent forward scattering, genuine interferential signature of Anderson localization. The third is the direct measurement of the β(g) scaling function in two different symmetry classes, allowing to demonstrate its universality and the one-parameter scaling hypothesis.
Anderson localization is the ubiquitous phenomenon of inhibition of transport of classical and quantum waves in a disordered medium. In dimension one, it is well known that all states are localized, ...implying that the distribution of an initially narrow wave packet released in a disordered potential will, at long time, decay exponentially on the scale of the localization length. However, the exact shape of the stationary localized distribution differs from a purely exponential profile and has been computed almost fifty years ago by Gogolin. Using the atomic quantum kicked rotor, a paradigmatic quantum simulator of Anderson localization physics, we study this asymptotic distribution by two complementary approaches. First, we discuss the connection of the statistical properties of the system’s localized eigenfunctions and their exponential decay with the localization length of the Gogolin distribution. Next, we make use of our experimental platform, realizing an ideal Floquet disordered system, to measure the long-time probability distribution and highlight the very good agreement with the analytical prediction compared to the purely exponential one over 3 orders of magnitude.
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