Self-Kerr Effect across the Yellow Rydberg Series of Excitons in Cu_{2}O

We investigate the nonlinear refraction induced by Rydberg excitons in Cu_{2}O. Using a high-precision interferometry imaging technique that spatially resolves the nonlinear phase shift, we observe significant shifts at extremely low laser intensity near each exciton resonance. From this, we derive the nonlinear index n_{2}, present the n_{2} spectrum for principal quantum numbers n≥5, and report large n_{2} values of order 10^{-3}  mm^{2}/mW. Moreover, we observe a rapid saturation of the Kerr nonlinearity and find that the saturation intensity I_{sat} decreases as n^{-7}. We explain this with the Rydberg blockade mechanism, whereby giant Rydberg interactions limit the exciton density, resulting in a maximum phase shift of 0.5 rad in our setup.

Fractional Derivative Modification of Drude Model

A novel, two-parameter modification of a Drude model, based on fractional time derivatives, is presented. The dielectric susceptibility is calculated analytically and simulated numerically, showing good agreement between theoretical description and numerical results. The absorption coefficient and wave vector are shown to follow a power law in the frequency domain, which is a common phenomenon in electromagnetic and acoustic wave propagation in complex media such as biological tissues. The main novelty of the proposal is the introduction of two separate parameters that provide a more flexible model than most other approaches found in the literature. Moreover, an efficient numerical implementation of the model is presented and its accuracy and stability are examined. Finally, the model is applied to an exemplary soft tissue, confirming its flexibility and usefulness in the context of medical biosensors.

Fractal Plasmons on Cantor Set Thin Film

The propagation of surface plasmon–polaritons is investigated in a metallic, fractal-like structure based on Cantor set. The dynamic of plasmonic modes generating on the Cantor structure is discussed in the context of the setup geometry. The numerically obtained reflection spectra are analyzed with the box-counting method to obtain their dimension, which is shown to be dependent on the geometry of the plasmonic structure. The entropy of the structure is also calculated and shown to be proportional to the dimension. Presented analysis allows for extracting information about fractal plasmonic structure from the reflectance spectrum. Predictions regarding the experimental observation of discussed effects are presented.

Solid-state pulsed microwave emitter based on Rydberg excitons

We theoretically demonstrate how the cuprous oxide Cu ₂O could be used as a gain medium in a solid-state maser. By taking advantage of radiative microwave transitions between highly excited Rydberg states, one can achieve population inversion and masing in a wide range of wavelengths. In the pulsed emission regime, the considered excitonic system is characterized by intricate and rich dynamics, which are investigated numerically, taking into account several key features of the medium, such as strong Stark shift of energy levels and the presence of the Rydberg blockade effect.

Proposal of tunable Rydberg exciton maser

We propose a continuous-mode solid-state maser based on Cu₂O, where ensemble of highly excited Rydberg exciton states serves as a gain medium. We show that the system is highly tunable with an external electric field, allowing for a wide range of emission frequencies within terahertz range. Numerical simulations of the system dynamics are performed to optimize the conditions for efficient masing and estimate the emission power.

Ultraslow long-living plasmons with electromagnetically induced transparency

We analytically examine propagation of surface plasmon polaritons (SPPs) at a thin metallic film between a glass substrate and an electromagnetically induced transparency (EIT) medium. High precision and high resolution in the frequency domain provided by EIT paves the way toward plasmonic group velocities' reduction, even by up to four orders of magnitude, and corresponding lifetime enhancement of SPPs up to microseconds.