We present a microwave experimental setup emulating tight-binding systems that is now widely used in the realm of topological photonics. A thorough description of the experimental building blocks is presented, showing the advantages and the limits of this platform. Various experimental realizations are then described, ranging from the selective enhancement of a defect state in a non-Hermitian Su-Schrieffer-Heeger (SSH) chain, to the generation of giant pseudo-magnetic fields in deformed honeycomb lattices. Introducing nonlinear losses, the interplay between nonlinearity and topological protection can be engineered to realize a nonlinearly functionalized topological mode with promising applications in receiver protection.
Coherent perfect absorption is one of the possibilities to get high absorption but typically suffers from being a resonant phenomena, i.e., efficient absorption only in a local frequency range. Additionally, if applied in high power applications, the understanding of the interplay of non-linearities and coherent perfect absorption is crucial. Here we show experimentally and theoretically the formation of non-linear coherent perfect absorption in the proximity of exceptional point degeneracies of the zeros of the scattering function. Using a microwave platform, consisting of a lossy nonlinear resonator coupled to two interrogating antennas, we show that a coherent incident excitation can trigger a self-induced perfect absorption once its intensity exceeds a critical value. Note, that a (near) perfect absorption persists for a broad-band frequency range around the nonlinear coherent perfect absorption condition. Its origin is traced to a quartic behavior that the absorbance spectrum acquires in the proximity of the exceptional points of the nonlinear scattering operator.
Receiver protectors (RPs) shield sensitive electronics from high-power incoming signals that might damage them. Typical RP schemes range from simple fusing and PIN diodes, to superconducting circuits and plasma cells -each having a variety of drawbacks associated with unacceptable system downtime and self-destruction, to significant insertion losses and power consumption. Here, we theoretically propose and experimentally demonstrate a unique self-shielding RP based on a coupled-resonator-microwave-waveguide (CRMW) with a topological defect being inductively coupled to a diode. This RP utilizes a charge-conjugation (C) symmetric resonant defect mode that is robust against disorder and demonstrates high transmittance at low incident powers. When incident power exceeds a critical value, a self-induced resonant trapping effect occurs leading to a dramatic suppression of transmittance and a simultaneous increase of the reflectance close to unity. The proposed RP device is self-protected from overheating and electrical breakdown and can be utilized in radars, reflection altimeters, and a broad range of communication systems.
We present a microwave realization of a reflective topological limiter based on an explicit selfinduced violation of a charge-conjugation (CT ) symmetry. The starting point is a bipartite structure created by coupled dielectric resonators with a topological defect placed at the center and two lossy resonators placed on the neighboring sites of the defect. This defect supports a resonant mode if the CT -symmetry is present, while it is suppressed once the symmetry is violated due to permittivity changes of the defect resonator associated with high irradiances of the incident radiation. This destruction leads to a suppression of transmittance and a subsequent increase of the reflectance while the absorption is also suppressed.
Shaping single-mode operation in high-power fibers requires a precise knowledge of the gain-medium optical properties. This requires precise measurements of the refractive index differences (Δn) between the core and the cladding of the fiber. We exploit a quantum optical method based on low-coherence Hong-Ou-Mandel interferometry to perform practical measurements of the refractive index difference using broadband energy-time entangled photons. The precision enhancement reached with this method is benchmarked with a classical method based on single photon interferometry. We show in classical regime an improvement by an order of magnitude of the precision compared to already reported classical methods. Strikingly, in the quantum regime, we demonstrate an extra factor of 4 on the precision enhancement, exhibiting a state-of-the-art Δn precision of 6 × 10−7. This work sets the quantum photonics metrology as a powerful characterization tool that should enable a faster and reliable design of materials dedicated to light amplification.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.