Current Physics - Current Issue

This research puts forward a cost-efficient high-efficiency plasmonic photonic crystal sensor for biomedical applications that functions in the near-infrared range.

The sensor design is composed of multiple two-dimensional photonic crystal layers stacked in the order of SiO2 foundational layer, graphite layer, MgF2 waveguide, and finally a gold ring over the top. The graphite layer is deposited for optimum sensing and high absorption peaks and is state-of-the-art in this research work. Metal deposition of the gold layer is used for harnessing plasmonic properties that play a vital role in detecting small refractive index changes.

The sensor design is investigated for a range of coupling incident angles and it is found that the sensor is responsive to a broad range of angles i.e., 0^o to 80^o. The proposed sensor has given output peak values of more than 90% in the whole range of incident source angles.

Finally, water and 25% concentration of glucose samples are used for investigating sensor performance and it is noted that the sensor’s sensitivity reaches as high as 1675 nm/RIU-1 with a Figure of Merit (FOM) of 20.94 RIU-1. The sensor’s numerical simulations have been performed using Finite Element Method (FEM) and Finite Difference Time Domain (FDTD).

Circular Rydberg States (CRS) were studied theoretically and experimentally in numerous works. In particular, in the previous paper by one of us, there were derived analytical expressions for the energy of classical CRS in collinear electric (F) and magnetic (B) fields of arbitrary strengths imposed on a hydrogenic system (atom or ion). For the magnetic field B of any strength, the author of that study gave formulas for the dependency of the classical ionization threshold Fc(B) and the energy at this threshold Ec(B). He also analyzed the stability of the motion by going beyond the CRS. In addition, for two important particular cases previously studied in the literature – classical CRS in a magnetic field only and classical CRS in an electric field only – some new results were also presented in that paper, especially concerning the Stark effect.

In the present paper, we study analytically axially-symmetric CRS of a heliumic system (He atom or He-like ion) subjected to an electric or magnetic field of arbitrary strength.

In this investigation, analytical techniques were applied.

We showed that in the case of the Stark effect, the difference in the unperturbed structure of the heliumic systems (compared to hydrogenic systems), i.e., the non-negligible size, causes the decrease of the classical ionization threshold, as well as increases the energy and the orbit radius of the outer electron at the ionization threshold. Also, the allowance for the non-negligible size of the internal subsystem increases the maximum possible absolute value of the induced electric dipole moment. In the case of the Zeeman effect, we demonstrated that the non-negligible size of the inner system increases the energy and the orbit radius of the outer electron.

The allowance for the non-negligible size of the internal subsystem can strongly affect the properties of the axially symmetric circular states. We believe that our results are of fundamental importance.

A model of quantum gravity unrelated to general relativity is described. The main postulate of the model is the assumption of the existence of a background of superstrongly interacting gravitons. To describe the interaction of a graviton with any particle during their collision, a new constant is introduced.

It is shown that screening of the background of single gravitons by a pair of bodies leads to approximately equal attractive and repulsive forces between the bodies. Pairing of a part of the background gravitons provided that the pairs are destroyed as a result of a collision with a body, yields an attractive force twice as great as the repulsive force, and gravity arises as an effect of background screening.

Newton’s constant has been calculated in the model as a function of background temperature, which allows the value of the new constant to be estimated. This model is free from divergences, unlike quantum gravity models based on general relativity, due to the specific shape of the Planck spectrum of the graviton background. A theoretical estimate of the Hubble constant, depending on the new constant, is also obtained.

An important feature of the model is the necessity of an “atomic” structure of matter, which leads as a side effect to the prohibition of the existence of black holes that do not have such a structure. Small additional effects of the model, caused by the interaction of photons with gravitons, may have great significance for cosmology.