In this paper, we propose a highly sensitive quasi-D-shaped fiber optic biosensor for detection of high refractive index (RI) liquid analytes via surface plasmon resonance. The main mechanism of sensing is interplay between photonic crystal fiber fundamental mode and plasmonic mode which leads to formation of different resonance peaks depending on the analyte RI. We numerically analyze the structure sensitivity to design parameters and demonstrate the sensing performance of the proposed biosensor using both spectral sensitivity and amplitude sensitivity methods. The proposed biosensor has a RI detection range of 0.15 refractive index unit (RIU) from 1.45 to 1.6. The sensor exhibits linear sensing performance with a RI spectral sensitivity of 9300 nm/RIU for analyte RI ranging from 1.45 to 1.525, 1176 nm/RIU for analyte RI ranging from 1.525 to 1.6 and in particular, 11800 nm/RIU for analyte RI between 1.475 and 1.5. Furthermore, an average RI sensitivity of 4800 nm/RIU for analyte RI ranging from 1.45 to 1.6 is demonstrated. We also study the amplitude sensitivities of the proposed sensor which show promising maximum values of 183.6 RIU-1 for 785 nm excitation and 820 RIU-1 for 1050 nm excitation. Due to the simple structure of the proposed biosensor, large detection range, high sensitivity and promising linear sensing performance, the proposed biosensor can be a promising candidate for detecting various high RI chemical and biochemical samples.

We consider a quadpartite hybrid system that incorporates a microwave cavity, a yttrium-iron-garnet (YIG) magnetic sphere resonator, a mechanical resonator, and an $LC$ electrical resonator. The entanglement and the quantum steering properties of this quadpartite system are thoroughly investigated by considering practical parameters. The microwave cavity mode is directly coupled to the magnon, mechanical, and electrical modes via Kittel magnetostatics, radiation pressure, and adjustable capacitance of the $LC$ configuration, respectively. We demonstrate tripartite entanglement among different modes, including indirectly coupled modes (such as magnon entanglement with mechanical and $LC$ electrical modes) for operating temperatures up to 2 K. Furthermore, we observe the presence of asymmetric one-way steering, revealing that the mechanical oscillator and the $LC$ resonant modes can steer the indirectly coupled magnon mode (yet in one direction while steering is not possible in the backward direction). The integration of the four interacting modes provides a variety of controlling degrees of freedom and makes the proposed quadpartite system an attractive approach for a wide range of applications, including data processing and communication, sensing, and quantum technologies.

We present a scheme to generate continuous-variable bipartite entanglement between two optical modes in a hybrid optical-microwave-plasmonic graphene waveguide system. In this scheme, we exploit the interaction of two light fields coupled to the same microwave mode via plasmonic graphene waveguide to generate two-mode squeezing, which can be used for continuous-variable quantum teleportation of the light signals over large distances. Furthermore, we study the teleportation fidelity of an unknown coherent state. The teleportation protocol is robust against the thermal noise associated with the microwave degree of freedom.

In this paper, we propose a novel quantum approach for microwave-to-optical conversion in a multilayer graphene structure. The graphene layers are electrically connected and pumped by an optical field. The physical concept is based on using a driving microwave signal to modulate the optical input pump by controlling graphene conductivity. Consequently, upper and lower optical sidebands are generated. To achieve low noise conversion, the lower sideband is suppressed by the multilayer graphene destruction resonance. A perturbation approach is implemented to model the effective permittivity of the electrically driven multilayer graphene. Subsequently, a quantum mechanical analysis is carried out to describe the evolution of the interacting fields. It is shown that a quantum microwave-to-optical conversion is achieved for miltilayer graphene of the proper length (i.e., number of layers). The conversion rate and the number of converted photons are evaluated according to several parameters. These include the microwave signal frequency, the microwave driving voltages, the graphene intrinsic electron density, and the number of graphene layers. Owing to multilayer dispersion and to the properties of graphene, it is shown that a significant number of photons (converted from microwave to optical frequency range) is achieved for microvolt microwave driving voltages. Furthermore, a frequency-tunable operation is achieved using this technique simply by modifying the optical pump frequency.

In this paper, we propose a novel technique for the phase-matched coupling and frequency conversion of terahertz (THz) waves. The principle of operation is based on nonlinear THz wave interaction in a graphene parallel plate waveguide filled with lithium niobate. The THz waves induce nonlinear polarization that modulates the effective permittivity of the waveguide by modifying the graphene conductivity. To model the evolution of the THz waves, small modulation amplitudes are presumed and a perturbation analysis is performed. First, two THz inputs (the pump and the signal) with distinct frequencies, that is, f ₁ and f ₂ , are considered. The two waves are coupled in a phase-matched fashion and show significant signal gain. Second, a third THz input with low intensity is considered at frequency f ₃ . Frequency conversion from f ₃ to a new frequency, that is, f ₄ , is attainable, assisted by the permittivity modulation induced by the co-propagating waves f ₁ and f ₂ . The generated frequency has a Ω = f ₁ - f ₂ frequency detuning from the f ₃ frequency, that is, f ₄ = f ₃ - (f ₁ - f ₂ ). Thus, tunable frequency conversion can be achieved by controlling f ₁ , f ₂ , or f ₃ . Our numerical estimations show viable gain and conversion efficiency over the entire THz range considered, from 0.1 to 2 THz. The proposed technique is compact, tunable, and (in principle) spans the entire THz range.