Binbin Yang

Photon–magnon coupled systems have established as a versatile platform for investigating hybrid coherent phenomena that bestow important applications in signal communication and transduction potentially extending to the quantum regime. Recently, near-field photon mode couplings leveraging microwave surface plasmon polaritons have emerged as a promising approach towards enhanced coupling strengths and tailored spectral features, primarily owing to their optimized mode profiles and high sensitivity to local dielectric environment. To date, most reports have focused only on a single, isolated surface plasmon mode (either traveling or localized) coupling to magnon modes; however, additional functionalities and novel control knobs can arise via further exploiting the interference between distinct modes. In this work, we investigate the transmission characteristics and the photon–magnon coupling when an interfering spoof surface plasmon polariton (SSPP) mode couples to a magnon mode. We use a Mach–Zehnder interferometer (MZI) structure that transforms the phase difference of the electromagnetic signals propagating on the two arms into amplitude interference, resulting in frequency-selective excitation of even and odd modes. By loading a ferrimagnetic Y 3 Fe 5 O 12 (YIG) disc at selective locations along the MZI structure, we observe strong and tunable photon–magnon couplings between the MZI’s SSPP modes and the YIG’s magnon mode, as well as a pronounced transmission nonreciprocity that is attributed to the coupling between the magnon modes and the rotating rf fields of the photon mode, whose origin can be attributed to the slow-wave propagation along the SSPP structure. Such a nonreciprocity is further tailored by the design of different MZI device symmetries.

Despite its wide acceptance, one of the most critical limitations of Terahertz wave technology is its high sensitivity to moisture. This limitation can, in turn, be exploited for use in moisture detection applications. This work presents a quantitative, non-invasive characterization of moisture content in standard gypsum drywall using Terahertz Time-Domain Spectroscopy (THz-TDS). With an increase in the moisture content of the drywall sample, experimental results indicated an increase in the dielectric properties such as the refractive index, permittivity, absorption coefficient, extinction coefficient, and dissipation factor. The demonstrated sensitivity to moisture establishes THz-TDS as a powerful tool for structural monitoring, hidden defect detection, and electromagnetic modeling of real-world building environments. Beyond material diagnostics, these findings have broader implications for THz indoor propagation studies, especially for emerging sub-THz and low THz communication technologies in 5G/6G and THz imaging of objects hidden behind the wall.

In this paper, we report a novel shape synthesis method for multi-mode dielectric resonator antennas (DRA) that combines characteristic mode analysis (CMA) and a binary genetic algorithm (BGA). This feed-independent optimization forms a non-canonical dielectric body from tetrahedral elements, shaping the geometry to support the required modal resonant frequencies and quality factors. A feed network is then designed to excite the corresponding modes for matched and decoupled responses. As a demonstration of the proposed design approach, two three-mode MIMO DRAs are synthesized from both a rectangular and a cylindrical volume to operate at 2.45 GHz. The synthesized MIMO DRA’s complex shape (based on rectangle) is then fabricated using Nanoparticle jetted zirconia. A combination of probe and slot feeds are employed to excite the desired modes. Due to the orthogonality of the characteristic modes and the careful design of the feeding network, isolation >20 dB is achieved between all ports.

Improving the photon-magnon coupling strength can be done by tuning the structure of microwave resonators to better interact with the magnon counterpart. Planar resonators accommodating unconventional photon modes beyond the half- and quarter-wavelength designs have been explored due to their optimized mode profiles and potentials for on-chip integration. Here, we designed and fabricated an actively controlled ring resonator supporting the spoof localized surface plasmons (LSPs), and implemented it in the investigation of photon-magnon coupling for hybrid magnonic applications. We demonstrated gain-assisted photon-magnon coupling with the YIG magnon mode under several different sample geometries. The achieved coupling amplification largely benefits from the high quality factor (Q-factor) due to the additional gain provided by a semiconductor amplifier, which effectively increases the Q-factor from a nearly null state (passive resonance) to more than 1000 for a quadrupole LSP mode. Our results suggest an additional control knob for manipulating photon-magnon coupled systems exploiting external controls of gain and loss.

This article proposes a novel compact wideband dielectric resonator antenna design that incorporates inhomogeneous material distribution in a cubic structure. Specifically, in this design, the cubic dielectric resonator antenna is divided into multiple small blocks, and a continuous genetic algorithm is employed to optimize the material property of each block in order to maximize the radiation bandwidth. As a result, a cubic dielectric resonator antenna with inhomogeneous material distributions is designed and tested. In measurement, the proposed compact dielectric resonator antenna design exhibits 64.9% impedance bandwidth (4.08–8 GHz), considerably higher than the bandwidth of the initial homogeneous dielectric resonator antenna. The maximum system gain achieved over the frequency range is 9 dB at 7 GHz, with a peak measured system efficiency of 90.6%.

Developing hybrid materials and structures for electromagnetic wave engineering has been a promising route towards novel functionalities and tunabilities in many modern applications. Despite its established success in engineering optical light and terahertz waves, the implementation of metaresonators operating in the microwave band is still emerging, especially the implementation of metaresonators that allow on-chip integration and size miniaturization, which is crucial for developing hybrid quantum systems in the microwave band. In this work, we present a microwave metaresonator consisting of split-ring and spiral resonators, and implement it for the investigation of photon-magnon coupling for hybrid magnonic applications. We observe broadened bandwidth of the split-ring modes augmented by the additional spiral resonator, and, by coupling the modes to a magnetic sample, the resultant photon-magnon coupling can be significantly enhanced by more than tenfold. Our work suggests that combinatorial, hybrid microwave resonators may be a promising approach towards future development and implementation of photon-magnon coupling in hybrid magnonic systems.