Differential global surface impedance (DGSI) model, a rigorous approach, has been applied to the analysis of three dimensional plasmonic circuits. This model gives a global relation between the tangential electric field and the equivalent surface electric current on the boundary of an object. This approach helps one bring the unknowns to the boundary surface of an object and so avoid volumetric discretization. It also eliminates the need for equivalent surface magnetic current consideration. Therefore, there is no need to evaluate the rather complex integral operator related to this current. This will result in a great reduction in computation time and memory resources. On the other hand, due to small field variations along the longitudinal direction of each boundary segment, it is suggested to use the two dimensional DGSI matrix in the analysis of a three dimensional plasmonic circuit. This leads to a much simpler formulation of the DGSI model. Besides, our numerical results verify that this simplifying assumption will not greatly affect the accuracy of the analysis. Plasmonic waveguides with different thicknesses along with a line coupler have been analyzed. The results are verified with the results of a commercial software as well as global surface impedance (GSI) model previously presented in the literature.

A four port network adder-subtractor module, for surface plasmon polariton (SPP) waves based on a ring resonator filter is proposed. The functionality of module is achieved by the phase difference manipulation of guided SPPs through different arms connected to the ring resonator. The module is designed using the concepts of a basic two port device proposed in this paper. It is shown that two port network eliminates odd, and transmits even SPP modes of a single source. Moreover, in the case of four-port adder (with two individual sources), it is elucidated that according to the location of each output port, one can achieve the consequent added or subtracted outputs, correspondingly. Two distinct peaks are observed in the transmission spectrum of adder and subtractor outputs, where increasing the individual source phase difference, leads to a red shift in the adder output, and a blue shift in the subtractor output peaks. The proposed module can be used as the building block for implementing arithmetic operations in plasmonic integrated circuits. The transmission line theory verifies the numerical simulation results, and demonstrates the functionality of the adder/subtractor module.

An important property of electromagnetic fields, which arises from the interaction between fields and chiral molecules, is called optical chirality. By enhancing this field property, while maintaining constant input power, we are able to increase absorption of circularly polarized light by chiral molecules of a certain handedness. This enhancement is achieved through the use of achiral plasmonic nano-particles in conjunction with the twisted metamaterials. Optical chirality enhancement (OCE) has an important application in sensing enantiomers of chiral molecules. Here, we present a preliminary scheme to measure enantiomeric excess in mixtures of chiral molecules using OCE boosted by twisted metamaterials. This scheme does not require measurement of a frequency shift in the circular dichroism response.

This study proposes a structure for graphene spaser (surface plasmon amplification by stimulated emission of radiation) and develops an electrostatic model for quantizing plasmonic modes. Using this model, one can analyze any spaser consisting of graphene in the electrostatic regime. The proposed structure is investigated analytically and the spasing condition is derived. We show that spasing can occur at some frequencies where the quality factor of plasmonic modes is higher than some particular minimum values. Finally, an algorithmic design procedure is proposed by which one can design a viable structure at a given frequency. As an example, a spaser with plasmon energy of 0. 1 eV is designed.

Nanostructures of noble metal materials have been used in organic solar cells for enhancement of performance and light trapping. In this study, we have introduced branched silver cauliflower-like nanopatterns as sub-wavelength structured metal grating in organic solar cells. Self-assembled fabrication process of branched nanopatterns was carried out on a bio-template of cicada wing nanonipple arrays using a gas aggregation dc magnetron sputtering nanocluster source without size filtration. The branched nanostructures provide surface gaps with dimensions near the organic exciton diffusion length, which prevents recombination of charge carriers. An increased power conversion efficiency of 14.8% compared to that of the planar device was achieved mainly due to the enhancement in the short-circuit current density. Besides, these branched cauliflower-like nanopatterns had enhanced optical light absorption in the solar cell as a result of enhancing the optical path length of the reflected light in the active layer and plasmonic effects of the noble metal material.