امیر مدنی

In this paper, the spectral characteristics of nanocomposite structurally chiral medium (NSCM) which is doped with metal nanoparticles have been studied. This medium consists of silver nanospheres that are irregularly placed inside a structurally chiral material whose dielectric properties can be represented by a resonant effective uniaxial tensor. The structurally chiral material is considered with locally a 42m point group symmetry. particular examples of one-dimensional photonic crystals are structurally chiral media such as chiral elastomers, cholesteric liquid crystals, or chiral sculptured thin films. They are continuously nonhomogeneous materials with a spiral variation of anisotropy along a fixed axis. They show the circular Bragg phenomenon (CBP), where a cohanded circularly polarized plane wave, collision normally, is highly reflected in a certain wavelength range, whereas a similar wave of the contrary handedness is transmitted. Tuning and switching of the Bragg phenomenon can be studied by utilization of the usually high sensitivity of SCM to external low-frequency electric or magnetic fields as well as to applied light, and inserting various types of defects into the structure. Another way to control the spectral properties of the structurally chiral material is by doping them with materials having strong optical resonance. This great optical resonance has been shown for a nanocomposite consisting of metallic nanospheres randomly dispersed in a transparent matrix, whereas the optical properties of the host materials lack resonant properties. In this work, we optimize the spectrum of the structurally chiral medium by adjusting the nanoparticle size. The dielectric function is an important parameter in the design and optimization of the plasmonic resonances of the nanostructures. This function is different for nanoparticles in terms of shape and size from the dielectric function of bulk material. In the desired dielectric function, the nanoparticle size f